STUDY DESIGN: Measurements, descriptive. OBJECTIVES: To describe a weight bearing method to assess bilateral hip abductor & external rotator muscle performance. BACKGROUND: The hip abductors and external rotators are important in maintaining lower extremity alignment during weight bearing tasks. As such, there is a need for a method to assess hip muscle performance in weight bearing. METHODS: The weight bearing method utilized a force transducer connected to a non-stretchable fabric strap positioned around the distal ends of both thighs (proximal to the lateral epicondyles). The force generation capacity was recorded with the participants in a semi-squat position (30° of hip and 50° of knee flexion). To establish the reliability of the measurement, 20 participants were tested on 2 separate days. Intraclass correlation coefficient (ICC_3,1) and Standard Error of Measurement were calculated to evaluate the test-retest reliability and inter-session consistency. The level of agreement between the muscle performance values obtained using the weight bearing method and the traditional non-weight bearing test in side-lying (dynamometer) was assessed using a linear correlation model. RESULTS: The weight bearing hip muscle performance assessment was reliable (ICC=0.99, 95% CI=0.97-0.99), and consistent (SEM = 0.02 N/kg). The measured strength using the weight bearing method was moderately associated with the strength values measured in non-weight bearing (r=0.75, p<0.01). CONCLUSIONS: The proposed weight bearing method to assess hip abductor & external rotator muscle performance can be used as a simple, economic, and reliable method to assess hip muscle strength.

J Orthop Sports Phys Ther, Epub 18 March 2013. doi:10.2519/jospt.2013.4412

KEY WORDS: abductor, external rotator, gluteus maximus, gluteus medius, hip, strength

STUDY DESIGN: Reliability study. OBJECTIVES: To determine the feasibility and reliability of using transcranial magnetic stimulation (TMS) to assess corticomotor excitability (CE) of the gluteus maximus. BACKGROUND: Sport-specific skill training targeting greater utilization of the gluteus maximus has been proposed as a method to reduce the incidence of noncontact knee injuries. The use of TMS to assess changes in CE may help to determine training-induced central mechanisms associated with gluteus maximus activation. METHODS: Within- and between-day reliability was measured in 10 healthy adults. The CE was measured by stimulating the gluteus maximus ìhotspotî at 120% and 150% of motor threshold, while subjects performed a double-leg bridge. An intraclass correlation coefficient (model 2,1), standard error of measurement, and minimal detectable change were calculated to determine the within- and between-day reliability for the following TMS variables: peak-to-peak motor-evoked potential (MEP) amplitudes, cortical silent period, and MEP latency. RESULTS: It is feasible to measure the CE of the gluteus maximus with TMS. The intraclass correlation coefficients for all TMS outcome measures ranged from 0.73 to 0.97. The ranges of minimal detectable change, with respect to mean values for each TMS variable, were larger for MEP amplitude (304.7-585.4 µV) compared to those for cortical silent period duration (25.3-40.8 milliseconds) and MEP latency (1.1-2.1 milliseconds). CONCLUSION: The present study demonstrated a feasible method for using TMS to measure CE of the gluteus maximus. Small minimal detectable change values for the cortical silent period and MEP latency provide a reference for future studies.

J Orthop Sports Phys Ther 2013;43(4):214-221. Epub 13 March 2013. doi:10.2519/jospt.2013.4188

KEY WORDS: corticomotor excitability, reliability, transcranial magnetic stimulation

STUDY DESIGN: Controlled laboratory study, repeated-measures design. OBJECTIVES: To compare hip abductor muscle activity during selected exercises using fine-wire electromyography, and to determine which exercises are best for activating the gluteus medius and the superior portion of the gluteus maximus, while minimizing activity of the tensor fascia lata (TFL). BACKGROUND: Abnormal hip kinematics (ie, excessive hip adduction and internal rotation) has been linked to certain musculoskeletal disorders. The TFL is a hip abductor, but it also internally rotates the hip. As such, it may be important to select exercises that activate the gluteal hip abductors while minimizing activation of the TFL. METHODS: Twenty healthy persons participated. Electromyographic signals were obtained from the gluteus medius, superior gluteus maximus, and TFL muscles using fine-wire electrodes as subjects performed 11 different exercises. Normalized electromyographic signal amplitude was compared among muscles for each exercise, using multiple 1-way repeated-measures analyses of variance. A descriptive gluteal-to-TFL muscle activation index was used to identify preferred exercises for recruiting the gluteal muscles while minimizing TFL activity. RESULTS: Both gluteal muscles were significantly (P<.05) more active than the TFL in unilateral and bilateral bridging, quadruped hip extension (knee flexed and extending), the clam, sidestepping, and squatting. The gluteal-to-TFL muscle activation index ranged from 18 to 115 and was highest for the clam (115), sidestep (64), unilateral bridge (59), and both quadruped exercises (50). CONCLUSION: If the goal of rehabilitation is to preferentially activate the gluteal muscles while minimizing TFL activation, then the clam, sidestep, unilateral bridge, and both quadruped hip extension exercises would appear to be the most appropriate.

J Orthop Sports Phys Ther 2013;43(2):54-64. Epub 16 November 2012. doi:10.2519/jospt.2013.4116

KEY WORDS: EMG, gluteus maximus, gluteus medius, hip

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

J Orthop Sports Phys Ther 2012;42(6):A1-A54. doi:10.2519/jospt.2012.0301

KEY WORDS: knee, knee pain, PFP

The patient was a 27-year-old man who was a recreational baseball player. He was referred to a physical therapist for a suspected medial meniscus injury following a right-sided lower extremity twisting injury sustained 3 weeks prior. Despite 4 weeks of physical therapist intervention, the patient was unable to successfully return to athletic activities. The patient was then referred to an orthopaedic surgeon, who ordered magnetic resonance imaging of his right knee, which revealed a focal full-thickness chondral lesion at the median patellar ridge.

J Orthop Sports Phys Ther 2012;42(3):291. doi:10.2519/jospt.2012.0404

KEY WORDS: knee, magnetic resonance imaging, MRI

STUDY DESIGN: Randomized controlled trial. OBJECTIVES: To examine the effectiveness of isolated hip abductor and external rotator strengthening on pain, health status, and hip strength in females with patellofemoral pain (PFP). BACKGROUND: Altered hip kinematics resulting from hip muscle weakness has been proposed as a contributing factor in the development of PFP. To date, no study has examined clinical outcomes associated with isolated hip muscle strengthening in those with PFP. METHODS: Twenty-eight females with PFP were sequentially assigned to an exercise (n = 14) or a no-exercise control group (n = 14). The exercise group completed bilateral hip abductor and external rotator strengthening 3 times per week for 8 weeks. Pain (visual analog scale), health status (WOMAC), and hip strength (handheld dynamometer) were assessed at baseline and postintervention. Pain and health status were also evaluated at 6 months postintervention in the exercise group. Two-factor mixed-model analyses of variance were used to determine the effects of the intervention on each outcome variable. RESULTS: Significant group-by-time interactions were observed for each variable of interest. Post hoc testing revealed that pain, health status, and bilateral hip strength improved in the exercise group following the 8-week intervention but did not change in the control group. Improvements in pain and health status were sustained at 6-month follow-up in the exercise group. CONCLUSION: A program of isolated hip abductor and external rotator strengthening was effective in improving pain and health status in females with PFP compared to a no-exercise control group. The incorporation of hip-strengthening exercises should be considered when designing a rehabilitation program for females with PFP. LEVEL OF EVIDENCE: Therapy, level 2b.

J Orthop Sports Phys Ther 2012;42(1):22-29, Epub 25 October 2011. doi:10.2519/jospt.2012.3704

KEY WORDS: anterior knee pain, clinical trial, patella, rehabilitation, self-report

STUDY DESIGN: Prospective cohort study. OBJECTIVES: To characterize knee cartilage change in individuals with knee osteoarthritis (KOA) who have completed a therapeutic exercise program. BACKGROUND: While therapeutic exercise is frequently used successfully to improve pain and function in individuals with KOA, no studies have reported the volume of cartilage change or individual factors that may impact volume of cartilage change in those completing an exercise program for KOA. METHODS: Thirteen individuals with KOA underwent magnetic resonance imaging to quantify cartilage volume change in the weight-bearing regions of the medial and lateral femoral condyles and the entire surface of the tibial plateaus from baseline to 1-year follow-up. Body structure and function measures were taken for body mass index, knee axis alignment, knee motion, and knee strength. Activity limitations and activity levels were also measured prior to the therapeutic exercise program, using the Western Ontario and McMaster Universities Osteoarthritis Index and the Physical Activity Scale for the Elderly. At 6 months from baseline, follow-up clinical measurements of knee strength and motion were performed. At 1 year from baseline, imaging of the knee cartilage and knee alignment were performed, and participants completed the Western Ontario and McMaster Universities Osteoarthritis Index and Physical Activity Scale for the Elderly. RESULTS: The central region of the medial femoral condyle (cMF) had a median volume of cartilage loss of 3.8%. The other 3 knee tibiofemoral articular surfaces had minimal median cartilage volume change. Individuals were dichotomized into progressors (n = 6) and nonprogressors (n = 7), based on the standard error of measurement of cartilage volume change for the cMF. Progressors were younger, had a larger body mass index, had a higher Kellgren-Lawrence grade in the medial compartment of the knee, and had a greater increase in knee varus alignment from baseline to 1-year follow-up. The progressors also had frontal plane hip and knee kinetics during baseline gait analysis that potentially increased medial knee joint loading. CONCLUSION: The loss of cMF cartilage volume was highly variable and the median loss of cartilage was within the range previously reported. Seven of the 13 individuals did not have cMF cartilage volume loss greater than the standard error of measurement. Change in cartilage volume of the cMF may be influenced to a greater extent by personal factors than by completion of a therapeutic exercise program. Additional research is needed to decipher the interactions among therapeutic exercise and personal characteristics that impact knee cartilage loss.

J Orthop Sports Phys Ther 2011;41(10):708-722, Epub September 2011. doi:10.2519/jospt.2011.3633

KEY WORDS: arthritis, biomechanics, magnetic resonance imaging, MRI

STUDY DESIGN: Controlled laboratory study using a repeated-measures design. OBJECTIVE: To quantify patellofemoral joint reaction force (PFJRF) and stress (PFJS) during forward step-up (FSU), lateral step-up (LSU), and forward step-down (FSD) exercises. BACKGROUND: Although FSU, LSU, and FSD exercises are commonly used in patellofemoral joint rehabilitation programs, the influence of these stepping tasks on patellofemoral joint kinetics has not been quantified. METHODS: Three-dimensional lower extremity kinematics and kinetics and electromyographic (EMG) data were obtained from 20 healthy adults during their performance of FSU, LSU, and FSD exercises. The step height for each participant was adjusted to permit a standardized knee flexion angle of 45°. A previously described biomechanical model of the patellofemoral joint was used to quantify PFJRF and PFJS during each task. Peak PFJRF and PFJS during the concentric and eccentric phases of each step task were compared using a 2-factor analysis of variance (ANOVA). RESULTS: When collapsed across concentric and eccentric phases, peak PFJS was significantly greater during the FSD (mean ± SD, 13.8 ± 0.4 MPa) compared to the LSU (11.5 ± 0.8 MPa; P<.001) and FSU (11.2 ± 0.6 MPa; P = .002) exercises. Peak PFJRF also was significantly greater during the FSD (51.1 ± 2.7 N/kg) compared to the LSU (44.1 ± 3.4 N/kg; P<.001) and FSU (43.6 ± 2.3 N/kg; P = .023) exercises. CONCLUSION: In selecting exercises that promote lower extremity muscle strengthening while minimizing patellofemoral joint loading, LSU and FSU should be considered over FSD exercises, if the same step height is used.

J Orthop Sports Phys Ther 2011;41(4):241-248, Epub 2 February 2011. doi:10.2519/jospt.2011.3408

KEY WORDS: anterior knee pain, biomechanics, patella, patellofemoral pain syndrome, step exercises

STUDY DESIGN: Controlled laboratory study using a cross-sectional design. OBJECTIVES: To compare patellofemoral joint kinematics, femoral rotation, and patella rotation between females with patellofemoral pain (PFP) and pain-free controls using weight-bearing kinematic magnetic resonance imaging. BACKGROUND: Recently, it has been recognized that patellofemoral malalignment may be the result of femoral motion as opposed to patella motion. METHODS: Fifteen females with PFP and 15 pain-free females between the ages of 18 and 45 years participated in this study. Kinematic imaging of the patellofemoral joint was performed using a vertically open magnetic resonance imaging system. Axial-oblique images were obtained using a fast gradient-echo pulse sequence. Images were acquired at a rate of 1 image per second while subjects performed a single-limb squat. Measures of femur and patella rotation (relative to the image field of view), lateral patella tilt, and lateral patella displacement were made from images obtained at 45°, 30°, 15°, and 0° of knee flexion. Group differences were assessed using a mixed-model analysis of variance with repeated measures. RESULTS: When compared to the control group, females with PFP demonstrated significantly greater lateral patella displacement at all angles evaluated and significantly greater lateral patella tilt at 30°, 15°, and 0° of knee flexion. Similarly, greater medial femoral rotation was observed in the PFP group at 45°, 15°, and 0° of knee flexion when compared to the control group. No group differences in patella rotation were found. CONCLUSION: Altered patellofemoral joint kinematics in females with PFP appears to be related to excessive medial femoral rotation, as opposed to lateral patella rotation. Our results suggest that the control of femur rotation may be important in restoring normal patellofemoral joint kinematics.

J Orthop Sports Phys Ther 2010;40(5):277-285, Epub 12 March 2010. doi:10.2519/jospt.2010.3215

KEY WORDS: biomechanics (lower extremity), hip, knee, medical imaging, MRI

Patellofemoral pain syndrome (PFPS) is a clinical condition that is characterized by retropatellar and/or peripatellar pain associated with activities involving lower limb loading (eg, walking, running, jumping, stair climbing, and prolonged sitting and kneeling). PFPS is the most common overuse injury of the lower extremity, and is particularly prevalent in those who are physically active. While treatment for PFPS may be successful for the short-term, long-term results are less promising. The lack of long-term success in treating this condition may be due to the underlying etiologic factors not being addressed. While it is generally agreed that many factors can lead to PFPS, it is our contention that these factors are still not well-understood.

The mission of this first international research retreat was to bring scientists together from around the world who were conducting research aimed at understanding the factors that are related to the development, and consequently the treatment, of PFPS. These etiologic factors were classified as local, distal, and proximal. A call for abstracts for the retreat was made in the summer of 2008. All abstracts were peer-reviewed for scientific merit and relevance to the retreat. In the end, 32 abstracts were accepted for podium presentations and 11 were accepted as posters. In total, 55 participants from 10 countries, including Australia, Belgium, Brazil, Canada, Israel, Italy, the Netherlands, Singapore, United Kingdom, and the United States, contributed to the retreat.

The format of the 2-day meeting included 3 keynote presentations interspersed with 15-minute podium presentations and 5-minute poster presentations. This first retreat was held in Fells Point, Baltimore, Maryland and was hosted by the Division of Biokinesiology and Physical Therapy at the University of Southern California. Included in this PDF is a consensus statement, a listing of the presentations and authors, and abstracts of each of the presentations made at the conference.

J Orthop Sports Phys Ther 2010;40(3):A1-A48. doi:10.2519/jospt.2010.0302

KEY WORD: PFPS

SYNOPSIS: During the last decade, there has been a growing body of literature suggesting that proximal factors may play a contributory role with respect to knee injuries. A review of the biomechanical and clinical studies in this area indicated that impaired muscular control of the hip, pelvis, and trunk can affect tibiofemoral and patellofemoral joint kinematics and kinetics in multiple planes. In particular, there is evidence that motion impairments at the hip may underlie injuries such as anterior cruciate ligament tears, iliotibial band syndrome, and patellofemoral joint pain. In addition, the literature suggests that females may be more disposed to proximal influences than males. Based on the evidence presented as part of this clinical commentary, it can be argued that interventions which address proximal impairments may be beneficial for patients who present with various knee conditions. More specifically, a biomechanical argument can be made for the incorporation of pelvis and trunk stability, as well as dynamic hip joint control, into the design of knee rehabilitation programs. LEVEL OF EVIDENCE: Aetiology/therapy, level 5.

J Orthop Sports Phys Ther 2010;40(2):42-51. doi:10.2519/jospt.2010.3337

KEY WORDS: ACL, iliotibial band syndrome, patella, patellofemoral pain syndrome

STUDY DESIGN: Case report. OBJECTIVE: To highlight the effects of an intervention program consisting of strengthening and neuromuscular reeducation of the gluteus maximus in an elite triathlete with exercise-associated muscle cramping (EAMC). BACKGROUND: Researchers have described 2 theories concerning the etiology of EAMC: (1) muscle fatigue and (2) electrolyte deficit. As such, interventions for EAMC typically consist of stretching/strengthening of the involved muscle and/or supplements to restore electrolyte imbalances. CASE DESCRIPTION: The patient was a 42-year-old male triathlete with a primary complaint of recurrent cramping of his right hamstring muscle, which prevented him from completing races at his desired pace. Strength testing revealed gluteus maximus muscle weakness bilaterally. Electromyographic (EMG) analysis (surface electrodes, 1560 Hz) revealed that the right hamstrings were being activated excessively during terminal swing and the first half of the stance phase (48.1% maximum voluntary isometric contraction [MVIC]). OUTCOMES: Following the intervention, the patient was able to complete 3 triathlons without hamstring cramping. Strength testing revealed that the right hip extension strength improved from 35.6 to 54.7 kg, and activation of the hamstrings during terminal swing and the first half of the stance phase decreased to 36.4% of MVIC. DISCUSSION: A program of gluteus maximus strengthening and neuromuscular training eliminated EAMC of the hamstrings in this patient. Given that the hamstrings and gluteus maximus work as agonists to decelerate the thigh during terminal swing phase and control hip flexion during loading response of running, we postulate that strengthening of the gluteus maximus decreased the relative effort required by the hamstrings, thus reducing EAMC. The results of the EMG evaluation that was performed as part of this case report provides support for this hypothesis. LEVEL OF EVIDENCE: Therapy, level 4.

J Orthop Sports Phys Ther 2010;40(2):112-119, Epub 31 December 2009. doi:10.2519/jospt.2010.3110

KEY WORDS: hip, lower extremity, muscle cramping, running

STUDY DESIGN: Case report. OBJECTIVE: To describe an alternative treatment approach for piriformis syndrome using a hip muscle strengthening program with movement reeducation. BACKGROUND: Interventions for piriformis syndrome typically consist of stretching and/or soft tissue massage to the piriformis muscle. The premise underlying this approach is that a shortening or ìspasmî of the piriformis is responsible for the compression placed upon the sciatic nerve. CASE DESCRIPTION: The patient was a 30-year-old male with right buttock and posterior thigh pain for 2 years. Clinical findings upon examination included reproduction of symptoms with palpation and stretching of the piriformis. Movement analysis during a single-limb step-down revealed excessive hip adduction and internal rotation, which reproduced his symptoms. Strength assessment revealed weakness of the right hip abductor and external rotator muscles. The patientís treatment was limited to hip-strengthening exercises and movement reeducation to correct the excessive hip adduction and internal rotation during functional tasks. OUTCOMES: Following the intervention, the patient reported 0/10 pain with all activities. The initial Lower Extremity Functional Scale questionnaire score of 65/80 improved to 80/80. Lower extremity kinematics for peak hip adduction and internal rotation improved from 15.9° and 12.8° to 5.8° and 5.9°, respectively, during a step-down task. DISCUSSION: This case highlights an alternative view of the pathomechanics of piriformis syndrome (overstretching as opposed to overshortening) and illustrates the need for functional movement analysis as part of the examination of these patients. LEVEL OF EVIDENCE: Therapy, level 4.

J Orthop Sports Phys Ther 2010;40(2):103-111, Epub 31 December 2009. doi:10.2519/jospt.2010.3108

KEY WORDS: biomechanics, gluteus, hip pain, radiculopathy, sciatica

STUDY DESIGN: Clinical measurement, criterion standard. OBJECTIVES: To determine if the clinical measure of femoral anteversion is comparable to measures obtained from magnetic resonance imaging (MRI). An additional purpose of this study was to assess the intertester and intratester reliability of the clinical test. BACKGROUND: Femoral anteversion is commonly assessed as part of the physical examination; however, limited and inconsistent data exist on the validity and reliability of the clinical test. METHODS: Eighteen healthy adults (9 males, 9 females; mean ± SD age, 25.4 ± 3.3 years; body mass index, 22.9 ± 3.4 kg/m²) participated. Each underwent 3 data collection sessions: (1) MRI to measure femoral anteversion, (2) clinical testing of femoral anteversion, measured independently by 2 physical therapists, and (3) repeated clinical testing. Validity and reliability were assessed using intraclass correlation coefficient (ICC_2,3) and standard error of measurement (SEM). RESULTS: Moderate agreement was found between the clinical test and MRI measures of femoral anteversion (ICCs of 0.69 and 0.67 for examiners 1 and 2, respectively). The SEM was similar for both examiners (5.8° and 6.0°). Both intratester (ICCs of 0.88 and 0.90 for examiners 1 and 2, respectively) and intertester (ICC = 0.83) reliability was found to be substantial. CONCLUSIONS: In persons with a low body mass index, the clinical test to assess femoral anteversion was shown to exhibit substantial reliability, but only moderate agreement with MRI measurements. When performing the clinical test, one can be 95% confident that the true value of femoral anteversion will fall within 11.8° of the clinically measured value. This relatively wide confidence interval calls into question the clinical utility of the clinical test for assessing femoral anteversion.

J Orthop Sports Phys Ther 2009;39(8):586-592, Epub 24 June 2009. doi:10.2519/jospt.2009.2996

KEY WORDS: femur, hip morphology, medical imaging, physical examination

STUDY DESIGN: Controlled laboratory study using a cross-sectional, single testing session. OBJECTIVE: To determine the association between frontal plane knee excursion during a drop land task and measures of hip strength, and ankle and hip range of motion. BACKGROUND: Assessment of frontal plane knee excursion during a drop land task has been advocated as a means to screen for potentially injurious lower extremity movement patterns. Accordingly, an understanding of the physical characteristics associated with the magnitude of frontal plane knee excursion could assist clinicians in developing interventions and prevention strategies to minimize injury risk. METHODS AND MEASURES: Thirty-nine female high school soccer players (mean ± SD age, 15.5 ± 1.0 years; height, 162.2 ± 5.3 cm; body mass, 56.8 ± 6.7 kg) participated. Isometric hip muscle strength as well as ankle and hip range of motion measurements were obtained using standard clinical procedures and a handheld dynamometer. Frontal plane knee excursion was assessed using a 6-camera motion analysis system during a drop land task. Using 3-dimensional coordinate data, maximum frontal plane knee excursion was defined as the difference between the distances of right and left lateral knee markers at initial contact and maximum knee flexion during the deceleration phase of landing. Independent variables found to be significantly correlated with frontal plane knee excursion were then entered into a stepwise multiple regression procedure to determine the best set of predictors of this motion. RESULTS: Hip external rotation range of motion and ankle dorsiflexion range of motion were found to be negatively correlated with frontal plane knee excursion (r=-0.40, P=.005 and r=-0.27, P=.05, respectively). Together they accounted for 27% of the variance in frontal plane knee excursion (r=0.52, P=.03). No relationships between measures of hip strength and frontal plane knee excursion were found. CONCLUSIONS: Frontal plane knee excursion during a drop land task was partially attributed to available range of motion at the hip and ankle. These results suggest that range of motion of the joints proximal and distal to the knee should be considered when evaluating individuals who present with excessive frontal plane knee excursion during this task. Given that the relationship between range of motion and frontal plane knee excursion was small, other factors, including learned motor patterns, should be considered.

J Orthop Sports Phys Ther. 2008; 38(11):661-667; Epub 22 August 2008. doi:10.2519/jospt.2008.2695

KEY WORDS: knee injuries, kinematics, lower extremity, range of motion, strength

STUDY DESIGN: Controlled laboratory study using a cross-sectional design. OBJECTIVES: To determine whether females with patellofemoral pain (PFP) demonstrate differences in hip kinematics, hip muscle strength, and hip muscle activation patterns when compared to pain-free controls. BACKGROUND: It has been proposed that abnormal hip kinematics may contribute to the development of PFP. However, research linking hip function to PFP remains limited. METHODS AND MEASURES: Twenty-one females with PFP and 20 pain-free controls participated in this study. Hip kinematics and activity level of hip musculature were obtained during running, a drop jump, and a step-down maneuver. Isometric hip muscle torque production was quantified using a multimodal dynamometer. Group differences were assessed across tasks using mixed-design 2-way analyses of variance and independent t tests. RESULTS: When averaged across all 3 activities, females with PFP demonstrated greater peak hip internal rotation compared to the control group (mean ± SD, 7.6° ± 7.0° versus 1.2° ± 3.8°; P<.05). The individuals in the PFP group also exhibited diminished hip torque production compared to the control group (14% less hip abductor strength and 17% less hip extensor strength). Significantly greater gluteus maximus recruitment was observed for individuals in the PFP group during running and the step-down task. CONCLUSION: The increased peak hip internal rotation motion observed for females in the PFP group was accompanied by decreased hip muscle strength. The increased activation of the gluteus maximus in individuals with PFP suggests that these subjects were attempting to recruit a weakened muscle, perhaps in an effort to stabilize the hip joint. Our results support the proposed link between abnormal hip function and PFP. 

J Orthop Sports Phys Ther 2009;39(1):12-19, Epub 22 August 2008. doi:10.2519/jospt.2009.2885

KEY WORDS: biomechanics, kinematics, knee, motion analysis, patella

STUDY DESIGN: Resident's case problem. BACKGROUND: Recent literature has suggested that acetabular labral pathology secondary to femoroacetabular impingement (FAI) may be a precursor to early-onset hip osteoarthritis. The purpose of this resident's case problem was to explore the extent to which abnormal movement at the hip is a possible contributor to acetabular labral pathology. DIAGNOSIS: The patient was a 25-year-old female with a 4-year history of anterior-medial groin pain. Based on a combination of the clinical examination and magnetic resonance imaging findings, she was given a diagnosis of acetabular labral tear by her orthopaedic surgeon and referred to a physical therapist for assessment. Movement analysis during a single-leg step down, running, and a drop jump maneuver revealed excessive hip adduction and internal rotation on the involved side, which reproduced her symptoms. Application of a hip-strapping device resulted in decreased hip adduction and internal rotation, and an immediate decrease in symptoms. DISCUSSION: The reduction in pain secondary to controlling hip motion suggests that excessive frontal and transverse plane hip motions may contribute to FAI. Accordingly, physical therapy intervention aimed at controlling and reducing hip adduction and internal rotation during activities may be indicated in patients who present with this movement pattern associated with anterior hip/groin pain. LEVEL OF EVIDENCE: Differential diagnosis, level 4.

J Orthop Sports Phys Ther. 2008;38(9):558-565, published online 3 June 2008. doi:10.2519/jospt.2008.2790

KEY WORDS: biomechanics, FAI, femoroacetabular impingement, hip labrum, motion analysis

STUDY DESIGN: Experimental laboratory study. OBJECTIVES: To examine how a change in trunk position influences the kinematics, kinetics, and muscle activity of the lead lower extremity during the forward lunge exercise. BACKGROUND: Altering the position of the trunk during the forward lunge exercise is thought to affect the muscular actions of the lead lower extremity. However, no studies have compared the biomechanical differences between the traditional forward lunge and its variations. METHODS AND MEASURES: Ten healthy adults (5 males, 5 females; mean age ± SD, 26.7 ± 3.2 years) participated. Lower extremity kinematics, kinetics, and surface electromyographic (EMG) data were obtained while subjects performed 3 lunge exercises: normal lunge with the trunk erect (NL), lunge with the trunk forward (LTF), and lunge with trunk extension (LTE). A 1-way analysis of variance with repeated measures was used to compare lower extremity kinematics, joint impulse (area under the moment-time curve), and normalized EMG (highest 1-second window of activity for selected lower extremity muscles) among the 3 lunge conditions. RESULTS: During the LTF condition, significant increases were noted in peak hip flexion angle, hip extensor and ankle plantar flexor impulse, as well as gluteus maximus and biceps femoris EMG (P<.015) when compared to the NL condition. During the LTE condition, a significant increase was noted in peak ankle dorsiflexion and a significant decrease was noted in peak hip flexion angle (P<.015) compared to the NL condition. CONCLUSIONS: Performing a lunge with the trunk forward increased the hip extensor impulse and the recruitment of the hip extensors. In contrast, performing a forward lunge with the trunk extended did not alter joint impulse or activation of the lower extremity musculature. LEVEL OF EVIDENCE: Therapy, level 5.

J Orthop Sports Phys Ther. 2008;38(7):403-409, published online 15 April 2008. doi:10.2519/jospt.2008.2634

KEY WORDS: biomechanics, EMG, impulse, weight bearing

The patient was a 26-year-old female with a 14-year history of right-sided patellofemoral pain and frequent episodes of patellar subluxation/dislocation. Because of her longstanding history of patellofemoral pain and failure to respond to conservative management, magnetic resonance imaging was ordered. Axial and sagittal images of the patellofemoral joint revealed a bone spur on the anterior-medial surface of the femoral trochlear groove. After further consultation with an orthopedic surgeon, an arthroscopic surgical procedure was scheduled to remove the bone spur. At the time of publication, the subject was 1 month postsurgery and symptom free.

J Orthop Sports Phys Ther. 2008;38(3):158. doi:10.2519/jospt.2008.0403

KEY WORDS: magnetic resonance imaging, patellar subluxation/dislocation

Objective:To quantify patellofemoral joint reaction forces and stress while squatting with and without an external load.

Background: Although squatting exercises in the rehabilitation setting are often executed to a relatively shallow depth in order to avoid the higher joint forces associated with increased knee flexion, objective criteria for ranges of motion have not been established.

Methods and Measures: Fifteen healthy adults performed single-repetition squats to 90° of knee flexion without an external load and with an external load (35% of the subject’s body weight [BW]). Anthropometric data, three-dimensional kinematics, and ground reaction forces were used to calculate knee extensor moments (inverse dynamics approach), while a biomechanical model of the patellofemoral joint was used to quantify the patellofemoral joint reaction forces and patellofemoral joint stress. Data were analyzed during the eccentric (0–90°) and concentric (90–0°) phases of the squat maneuver.

Results: In both conditions, knee extensor moments, patellofemoral joint reaction forces, and patellofemoral joint stress increased significantly with greater knee flexion angles (P < 0.05). Peak patellofemoral joint force and stress was observed at 90° of knee flexion. Patellofemoral joint stress at 45°, 60°, 75°, and 90° of knee flexion during the eccentric phase, and at 75° and 90° during the concentric phase, was significantly greater in the loaded trials versus the unloaded trials.

Conclusion: The data indicate that during squatting, patellofemoral joint stress increases as the knee flexion angle increases, and that the addition of external resistance further increases patellofemoral joint stress. These findings suggest that in order to limit patellofemoral joint stress during squatting activities, clinicians should consider limiting terminal joint flexion angles and resistance loads.

J Orthop Sports Phys Ther. 2002; 32(4):141–148.

Key Words: biomechanics, knee, patellofemoral joint reaction force, patellofemoral joint stress

Objective:To determine the effects of patellar taping on knee kinetics, kinematics, and vastus lateralis muscle activity during stair ambulation in individuals with patellofemoral pain (PFP).

Background: Patellar taping is a common treatment technique for individuals with PFP. Specific data on whether patellar taping improves gait variables, however, are limited.

Methods and Measures: Ten subjects with a diagnosis of PFP were studied (5 men, 5 women). The subjects’ mean age, height, and mass were 36.5 ± 11.1 years, 173.1 ± 10.3 cm, and 70.9 ± 13.3 kg, respectively. Lower extremity kinematics, ground reaction forces, and vastus lateralis EMG were obtained simultaneously while subjects ascended and descended stairs, under taped and untaped conditions. Knee moments were calculated using inverse dynamics equations. Four 2 ×2 (tape condition x stair condition) ANOVAs for repeated measures were generated for cadence and average stance phase knee extensor moment, knee flexion angle, and EMG.

Results: On the average, a 92.6% reduction in pain was observed following the application of tape. Increases in cadence, knee flexion angles, and knee extensor moments were observed under the taped condition for both stair ascent and descent; however, no difference in average vastus lateralis EMG was found.

Conclusions: Although patellar taping resulted in decreased pain and increased knee extensor moments, knee flexion angles, and cadence during stair ambulation, the vastus lateralis EMG activity level did not change with taping. Based on data from the vastus lateralis, care must be taken if improved gait parameters indicate change in muscle recruitment.

J Orthop Sports Phys Ther. 2002; 32(1):3–10.

Key Words: biomechanics, gait, patella, physical therapy

The future of orthopaedic and sports physical therapy will ultimately depend on the combination of outcomes and mechanistic research. One could argue that clinic-based research meets our more immediate needs, however, basic and applied research is certainly necessary in the long term. We cannot afford to make the same mistake of the last 30 years by focusing too heavily on 1 type of research, as neither type can exist in isolation and both should be occurring simultaneously. The fact of the matter is that many of the future researchers in physical therapy are still being trained in basic and applied sciences laboratories and their potential contribution to physical therapy science cannot be ignored. Such research efforts should be viewed as opportunities and embraced by the granting agencies within the American Physical Therapy Association, whether it is the Foundation for Physical Therapy or individual sections. Ultimately, the combination of basic, applied, and clinical research will provide a more comprehensive scientific foundation for practice by ensuring that the immediate and future research needs of physical therapy are met.

J Orthop Sports Phys Ther. 2003;33(5):219-220.

Key Words: basic research, applied research

Although patellofemoral pain (PFP) is recognized as being one of the most common disorders of the lower extremity, treatment guidelines and underlying rationales remain vague and controversial. The premise behind most treatment approaches is that PFP is the result of abnormal patellar tracking and/or patellar malalignment. Given as such, interventions typically focus on the joint itself and have traditionally included strengthening the vastus medialis oblique, taping, bracing, soft tissue mobilization, and patellar mobilization. More recently, it has been recognized that the patellofemoral joint and, therefore, PFP may be influenced by the interaction of the segments and joints of the lower extremity. In particular, abnormal motion of the tibia and femur in the transverse and frontal planes may have an effect on patellofemoral joint mechanics. With this in mind, interventions aimed at controlling hip and pelvic motion (proximal stability) and ankle/foot motion (distal stability) may be warranted and should be considered when treating persons with patellofemoral joint dysfunction. The purpose of this paper is to provide a biomechanical overview of how altered lower-extremity mechanics may influence the patellofemoral joint. By addressing these factors, better long-term treatment success and prevention may be achieved.

J Orthop Sports Phys Ther. 2003;33(11):639-646.
 

Key Words: knee, patella, patellofemoral, pain

Study Design: Case report. Objective: To describe an alternative treatment approach for patellofemoral pain. Background: Weakness of the hip, pelvis, and trunk musculature has been hypothesized to influence lower-limb alignment and contribute to patellofemoral pain. Two patients who had a chief complaint of patellofemoral pain and demonstrated lack of control of the hip in the frontal and transverse planes during functional movements were treated with an exercise program targeting the hip, pelvis, and trunk musculature. Methods and Measures: The patients presented in these 2 case reports did not exhibit obvious patellar malalignment or tracking problems; however, on qualitative assessment, both demonstrated excessive hip adduction, internal rotation, and knee valgus during gait and while performing a step-down maneuver. In addition, both patients exhibited weakness of the hip abductors, extensors, and external rotators, as demonstrated by hand-held dynamometry testing. Treatment in both cases occurred over a 14-week period and focused on recruitment and endurance training of the hip, pelvis, and trunk musculature. Functional status, pain, muscle force production, as well as subjective and objective assessment of lower-extremity kinematics during gait and a step-down maneuver were assessed preintervention and postintervention. Results: Both patients experienced a significant reduction in patellofemoral pain, improved lower-extremity kinematics during dynamic testing, and were able to return to their original levels of function. Gluteus medius force production improved by 50% in patient A and 90% in patient B, while gluteus maximus force production improved 55% in patient A and 110% in patient B. Objective kinematic improvements in the step-down task also were demonstrated in patient A. Conclusion: Assessment and treatment of the hip, pelvis, and trunk musculature should be considered in the rehabilitation of patients who present with patellofemoral pain and demonstrate abnormal lower-extremity kinematics.

J Orthop Sports Phys Ther. 2003;33(11):642-660.
 

Key Words: case study, knee pain, lower-extremity rehabilitation, therapeutic exercise

Study Design: Single-group, repeated-measures design. Objective: To compare patellofemoral joint kinematics during weight-bearing and non–weight-bearing knee extension in persons with lateral subluxation of the patella. Background: The only previous study to quantify differences in patellofemoral joint kinematics during weight-bearing and non–weight-bearing tasks was limited in that static loading conditions were utilized. Differences in patellofemoral joint kinematics between weight-bearing and non–weight-bearing conditions have not been quantified during dynamic movement. Methods and Measures: Six females with a diagnosis of patellofemoral pain and lateral subluxation of the patella participated. Using kinematic magnetic resonance imaging, axial images of the patellofemoral joint were obtained as subjects extended their knees from 45° to 0° during non–weight-bearing (5% body weight resistance) and weight-bearing (unilateral squat) conditions. Measurements of patellofemoral joint relationships (medial/lateral patellar displacement and patellar tilt), as well as femur and patella rotations relative to an external reference system (ie, the image field of view), were obtained at 3° increments during knee extension. Results: During non–weight-bearing knee extension, lateral patellar displacement was more pronounced than during the weight-bearing condition between 30° and 12° of knee extension, with statistical significance being reached at 27°, 24°, and 21°. No differences in lateral patellar tilt were observed between conditions (P = .065). During the weight-bearing condition, internal femoral rotation was significantly greater than during the non–weight-bearing condition as the knee extended from 18° to 0°. During the non–weight-bearing condition, the amount of lateral patellar rotation was significantly greater than during the weight-bearing condition throughout the range of motion tested. Conclusions: The results of this study demonstrated that lateral patellar displacement was more pronounced during non–weight-bearing knee extension compared to weight-bearing knee extension in persons with lateral patellar subluxation. In addition, the results of this investigation suggest that the patellofemoral joint kinematics during non–weight-bearing could be characterized as the patella rotating on the femur, while the patellofemoral joint kinematics during the weight-bearing condition could be characterized as the femur rotating underneath the patella.

J Orthop Sports Phys Ther. 2003;33(11):677-685.
 

Key Words: magnetic resonance imaging, patellar tracking, patellofemoral joint

Study Design: Cross-sectional. Objective: To investigate the association between lumbar segmental motion and pain response during the application of a posterior-to-anterior (PA) force to the lumbar spinous processes in persons with nonspecific low back pain. Background: Although low back pain is believed to be associated with altered segmental motion of the lumbar spine, the relationship between subjective reports of pain and objective measurements of segmental motion has not been established. Methods and Measures: Thirty-five individuals between 18 and 45 years of age with nonspecific low back pain (less than 3 months’ duration) participated. All subjects participated in 2 separate procedures: (1) segmental motion assessment during a PA force application over the lumbar spinous processes using dynamic magnetic resonance imaging (MRI), and (2) pain assessment during a PA force application procedure outside of the MRI environment. Frequency counts were used to determine the lumbar segments that were most painful, and which functional spinal units had the most and least motion. Fisher exact tests were performed to determine if an association existed between the most painful segment and the functional spinal unit with the most or least motion. Results: L5 was deemed the most painful segment in nearly half of the participants (48.1%). The L1-2 and L3-4 functional spinal units most frequently had the most motion (25.9% each) and the L4-5 functional spinal units most frequently had the least motion (29.6%). No association was found between the most painful segment and the functional spinal units with either the most or least motion. Conclusion: The results of this study indicate that an assumption regarding segmental motion cannot be inferred from the pain response when using a PA force application procedure.

J Orthop Sports Phys Ther. 2005;35(4):203-209. doi:10.2519/jospt.2005.1479

Key Words: lumbar spine, manual therapy, painful segment

Study Design: Repeated measures design using a sample of convenience. Objective: To assess the criterion-related validity and intrarater reliability of a clinical measurement used for determining the medial/lateral position of the patella. Background: Patellar taping is a common treatment for patellofemoral pain. Application of this intervention requires accurate assessment of patellar orientation; however, the validity of this clinical procedure has not been documented. Methods and Measures: Fourteen subjects (10 women, 4 men; average age, 41 ± 16 years) were evaluated. Clinical assessment of medial/lateral patellar orientation using the technique described by McConnell was compared with the actual position of the patella as determined through magnetic resonance imaging (MRI). Imaging was done on 7 knees of 4 subjects who were asymptomatic and 11 knees of 10 subjects who were symptomatic. Both clinical and MRI assessments were made with the subjects supine, the knee extended, and the quadriceps relaxed. Agreement between the 2 techniques and the intrarater reliability of each measurement were quantified by means of the intraclass correlation coefficient (ICC). Results: Both the clinical and MRI measures of medial/lateral patellar displacement were found to demonstrate good intrarater reliability (ICC = 0.91 and 0.85, respectively). The agreement between the clinical and MRI determinations of medial/lateral patellar position was poor (ICC = 0.44). The average amount of lateral patellar displacement as determined by the clinical method was more than twice that established through MRI. Conclusions: The clinical assessment of the medial/lateral position of the patella overestimates the true amount of lateral patellar displacement. A more valid clinical method of assessing the medial/lateral component of patellar orientation is necessary.

J Orthop Sports Phys Ther. 1999;29(7):372-377,386-393.

Key Words: magnetic resonance imaging, patellar displacement, patellofemoral joint

Patellofemoral pain is one of the most common knee disorders seen in orthopaedic practice. Despite its high incidence, treatment of this disorder remains controversial. Traditionally, nonoperative management of patellofemoral pain has focused on restoring normal patellar tracking by improving dynamic stability. Of particular interest to clinicians has been the vastus medialis oblique, which has been implicated as being the primary medial stabilizer of the patella. Although emphasis on the vastus medialis oblique continues to be the mainstay of conservative care of patellofemoral pain, there exists considerable disagreement between research outcomes and clinical practice. This article critically reviews the current literature concerning the treatment of patellofemoral pain with respect to the vastus medialis oblique, taping, and bracing, as well as various forms of therapeutic exercise, and relates these findings to the prevailing views regarding the management of this disorder.

J Orthop Sports Phys Ther. 1998;28(5):345-354.

Key Words: patellofemoral pain, rehabilitation, vastus medialis oblique

Although patellar taping has been reported to be effective in reducing pain, the effects of this procedure on functional outcomes, such as ambulation, have not been documented. The purpose of this study was to compare stride characteristics and joint motion in subjects with patellofemoral pain, with and without the application of patellar taping using the McConnell technique. Fifteen female subjects between the ages of 14 and 41 years with a diagnosis of patellofemoral pain participated in this study. Stride characteristics (Stride Analyzer) and sagittal plane joint motion (VICON) were recorded simultaneously during taped and untaped trials of free walking, fast walking, and ascending and descending a ramp and stairs. A repeated measures analysis of variance was used to determine differences between taped and untaped trials. Although subjects reported an average pain reduction of 78% using a visual analogue scale, the only significant change in stride characteristics was an increase in stride length during ramp ascent. Patellar taping did, however, result in a small but significant increase in loading response knee flexion across all conditions tested. We believe this finding demonstrates more willingness by the patellofemoral pain subjects to load the knee joint, thus permitting increased shock absorption, increased quadriceps activity, and tolerance of increased patellofemoral joint reaction force.

J Orthop Sports Phys Ther. 1997;26(6):286-291.

Key Words: patellofemoral pain, patellar taping, gait

The relationship between structural foot deformities and excessive subtalar joint pronation as being contributory to patellofemoral pain has not been well documented. It was the purpose of this study to assess the rearfoot posture in patients diagnosed with patellofemoral pain compared with a normal population. In addition, the intratester reliability in obtaining rearfoot measurements was assessed for right and left sides in 21 normal subjects. A goniometer was used to measure rearfoot posture in 30 female subjects (15 with patellofemoral pain and 15 controls). Measurements were taken with the subjects prone and the subtalar joint in neutral. Intraclass correlation coefficients were good for both the right and left measurements (0.87 and 0.86, respectively). A small but significant increase in rearfoot varus was found in the patellofemoral pain group compared with the control group (8.9° vs. 6.8°; p = .0002). These results suggest that increased rearfoot varus may be a contributing factor in patellofemoral pain and should be assessed when evaluating the events at the subtalar joint and the lower extremity. In addition, it has been demonstrated that an individual clinician can obtain consistent rearfoot measurements.

J Orthop Sports Phys Ther. 1995;22(4):155-160.

Key Words: patellofemoral, pain, rearfoot

At the time this study was conducted, there were no financial conflicts of interest with any of the authors. Subsequently, a version of the device described in this manuscript was manufactured and marketed by Matsumoto Prosthetics and Orthotics Manufacturing Co, LTD, located in Nagoya, Japan. Mr. Ota has a financial interest with this arrangement and acknowledges a potential conflict of interest.

Study Design: Repeated-measures, within-subject design.
Objective: To assess the concurrent criterion-related validity and reliability of a clinical device to quantify lateral patellar displacement.
Background: Excessive lateral displacement of the patella is an impairment that is widely associated with patellofemoral pain and/or pathology. Currently, no valid or reliable clinical method to assess lateral patellar displacement has been described in the literature.
Methods and Measures: A total of 26 individuals (14 asymptomatic and 12 symptomatic; mean ± SD age, 27 ± 4 years) participated in the validity portion of this study, while an additional 10 asymptomatic volunteers (mean ± SD age, 28 ± 5 years) participated in the reliability portion. Lateral displacement of the patella was assessed using a custom-designed patellofemoral arthrometer (PFA) and was compared to actual position of the patella as determined by magnetic resonance imaging (MRI). Both PFA and MRI measurements of lateral patellar displacement were made with the knee extended and the quadriceps contracted. The intraclass correlation coefficient (ICC) was used to assess the level of agreement between the PFA and MRI measurements, as well as the intrarater and interrater reliability of the PFA measurements.
Results: The ICC assessing the level of agreement between the MRI and PFA measures of lateral patellar displacement was good (0.86). Excellent intratester (ICC, 0.96 and 0.97) and intertester reliability (ICC, 0.92) were demonstrated.
Conclusion: Our results suggest that reasonable estimations of lateral patellar displacement can be obtained using the PFA.

J Orthop Sports Phys Ther. 2006;36(9):645-652. doi:10.2519/jospt.2006.2263

Key Words: knee, magnetic resonance imaging, patellar tracking, patellofemoral  joint