STUDY DESIGN: Cross-sectional. OBJECTIVE: To determine if females presenting with patellofemoral pain syndrome (PFPS) from no discernable cause other than overuse demonstrate hip weakness and increased hip internal rotation, hip adduction, and knee valgus during stair descent. BACKGROUND: Historically, PFPS has been viewed exclusively as a knee problem. Recent findings have indicated an association between hip weakness and PFPS. Researchers have hypothesized that patients who demonstrate hip weakness would exhibit increased hip internal rotation, hip adduction, and knee valgus during functional activities. To date, researchers have not simultaneously examined hip and knee strength and kinematics in subjects with PFPS to make this determination. METHODS AND MEASURES: Eighteen females diagnosed with PFPS and 18 matched controls participated. Strength measures were taken for the hip external rotators and hip abductors. Hip and knee kinematics were collected as subjects completed a standardized stair-stepping task. Independent t tests were used to determine between-group differences in strength and kinematics during stair descent. RESULTS: Subjects with PFPS generated 24% less hip external rotator (P = .002) and 26% less hip abductor (P =. 006) torque. No between-group differences (P > .05) were found for average hip and knee transverse and frontal plane angles during stair descent. CONCLUSION: Subjects with PFPS had significant hip weakness but did not demonstrate altered hip and knee kinematics as previously theorized. Additional investigations are needed to better understand the association between hip weakness and PFPS etiology. LEVEL OF EVIDENCE: Symptom Prevalence, Level 4.

J Orthop Sports Phys Ther. 2008;38(1):12-18, published online 21 November 2007, doi:10.2519/jospt.2008.2462

KEY WORDS: anterior knee pain, hip abduction, hip external rotation, kinematics

Study Design: Single-occasion, repeated-measures design. Objective: To determine the magnitude of hip abductor muscle activation during 6 rehabilitation exercises. Background: Many researchers have reported that hip strengthening, especially of the hip abductors, is an important component of a lower extremity rehabilitation program. Clinicians employ non–weight-bearing and weight-bearing exercise to strengthen the hip musculature; however, researchers have not examined relative differences in muscle activation during commonly used exercises. Information regarding these differences may provide clinicians with a scientific rationale needed for exercise prescription. Methods and Measures: Sixteen healthy subjects (mean ± SD age, 27 ± 5 years; range, 18-42 years; mean ± SD height, 1.7 ± 0.2 m; mean ± SD body mass, 76 ± 15 kg) volunteered for this study. Bipolar surface electrodes were applied to the right gluteus medius muscle. We measured muscle activation as subjects performed 3 non–weight-bearing (sidelying right hip abduction and standing right hip abduction with the hip at 0° and 20° of flexion) and 3 weight-bearing (left-sided pelvic drop and weight-bearing left hip abduction with the hips at 0° and 20° of flexion) exercises. Data were expressed as a percent of maximum voluntary isometric contraction of the right gluteus medius. Differences in muscle activation across exercises were determined using a 1-way analysis of variance with repeated measures, followed by a sequentially rejective Bonferroni post hoc analysis to identify differences between exercises. Results: The weight-bearing exercises demonstrated significantly greater EMG amplitudes (P<.001) than all non–weight-bearing exercises except non–weight-bearing sidelying hip abduction. Conclusion: The weight-bearing exercises and non–weight-bearing sidelying hip abduction exercise resulted in greater muscle activation because of the greater external torque applied to the hip abductor musculature. Although the non–weight-bearing standing hip abduction exercises required the least activation, they may benefit patients who cannot safely perform the weight-bearing or sidelying hip abduction exercises. Clinicians may use results from this study when designing hip rehabilitation programs.

J Orthop Sports Phys Ther. 2005;35(8):487-494. doi:10.2519/jospt.2005.2066

Key Words: gluteus medius, strengthening exercises, surface EMG

Clinicians routinely have used functional performance tests as an evaluation tool in deciding when an athlete can safely return to unrestricted sporting activities. These practitioners assumed that these tests provide a reliable measure of lower extremity performance; however, little research has been reported on the reliability of these measures. The purpose of this investigation was to determine the reliability of lower extremity functional performance tests. Five male and 15 female volunteers were evaluated using the single hop for distance, triple hop for distance, 6-m timed hop, and crossover hop for distance as described by Noyes (10). One clinician measured each subject's performance using a standardized protocol and retested subjects in the same manner approximately 48 hours later. The order of testing was randomly determined. Subjects' average and individual scores on each functional performance test were used for statistical analysis. Intraclass correlation coefficients (ICCs) and standard error of measurement (SEM) values based on average day 1 and day 2 scores were used to estimate the reliability of each functional performance test. Intraclass correlation coefficients were .96, .95, and .96, and SEMs were 4.56 cm, 15.44 cm, and 15.95 cm, respectively, for the single hop, triple hop, and crossover hop for distance tests. An ICC of .66 and SEM of.13 seconds for the 6-m timed hop resulted from limited variability between measurements; however, its small SEM value inferred that the inconsistency of measurement would occur in an acceptably small range. A repeated measures analysis of variance revealed no significant difference (p > .05) between individual trial scores except for the single hop for distance. We concluded that this difference represented a learning effect not found with the other tests. The results of this investigation demonstrate that clinicians can use functional performance testing to obtain reliable measures of lower extremity performance when using a standardized protocol.

J Orthop Sports Phys Ther. 1997;26(3):138-142.

Key Words: reliability, functional performance tests, lower extremity dysfunction