STUDY DESIGN: A case-control study, with single observation. OBJECTIVES: To compare the onset timing and activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) between subjects with and without patellofemoral pain syndrome (PFPS) at various step heights. BACKGROUND: It has been theorized that delayed or reduced VMO activity relative to the VL contributes to lateral patellar tracking and PFPS. However, conflicting evidence exists in the literature regarding this proposed mechanism. The lack of agreement among studies may be attributed to inconsistent knee flexion angles used in previous studies. METHODS AND MEASURES: Twenty subjects with PFPS (mean ± SD age, 29.5 ± 10 yrs) and 20 control subjeccts (mean ± SD age, 25.4 ± 3.1 yrs) ascended 5 different step heights, while knee kinematics and quadriceps EMG data were collected. Knee flexion angle at foot-step contact, VMO-VL onset timing, and VMO/VL activation ratios were analyzed between groups and step heights using 2-factor analyses of variance (ANOVAs) with repeated measures (α = .05). RESULTS: Individuals with PFPS demonstrated 4.7° (P = .038) more knee flexion at foot-step contact than control subjects. Despite greater knee flexion with increased step height (P‹.001), no differences in onset timing or activation magnitude ratio were present between groups or across step heights. However, individuals with PFPS displayed a significantly increased activation duration ratio compared to the control group (P = .043). CONCLUSION: Quadriceps onset timing and activation magnitude during stair ascent was similar between individuals with and without PFPS, regardless of step height. Thus, the results of this study are in agreement with evidence indicating no difference in VMO-VL timing and VMO/VL activation magnitude ratio between individuals with and without PFPS.

J Orthop Sports Phys Ther. 2007;37(5):239-244; published online 15 March 2007. doi:10.2519/jospt.2007.2421

KEY WORDS: activation ratio, anterior knee pain, EMG, onset delay, stair climbing

STUDY DESIGN: Prospective cohort. OBJECTIVE: To determine (1) the cumulative seasonal incidence and overall injury rate of medial tibial stress syndrome (MTSS) and (2) risk factors for MTSS with a primary focus on the relationship between navicular drop values and MTSS in high school cross-country runners. BACKGROUND: MTSS is a common injury among runners. However, few studies have reported the injury rate and risk factors for MTSS among adolescent runners. METHODS AND MEASURES: Data collected included measurement of bilateral navicular drop and foot length, and a baseline questionnaire regarding the runner’s height, body mass, previous running injury, running experience, and orthotic or tape use. Runners were followed during the season to determine athletic exposures (AEs) and occurrence of MTSS. RESULTS: The overall injury rate for MTSS was 2.8/1000 AEs. Although not statistically different, girls had a higher rate (4.3/1000 AEs) than boys (1.7/1000 AEs) (P = .11). Logistic regression modeling indicated that only gender and body mass index (BMI) were significantly associated with the occurrence of MTSS. However, when controlled for orthotic use, only BMI was associated with risk of MTSS. No significant associations were found between MTSS and navicular drop or foot length. CONCLUSIONS: Our findings suggest that navicular drop may not be an appropriate measure to identify runners who may develop MTSS during a cross-country season; thus, additional studies are needed to identify appropriate preseason screening tools.  

J Orthop Sports Phys Ther. 2007;37(2):40-47. doi:10.2519/jospt.2007.2343 

KEY WORDS: injury risk, female athlete, navicular drop, shin splints

Study Design: Two-group posttest-only comparison. Objective: To assess the influence of the Q-angle on the 3-dimensional lower extremity kinematics during running. Background: An excessive Q-angle has been implicated in the development of knee injuries by altering the lower extremity locomotion kinematics. Previous investigations using 2-dimensional analyses during walking did not support this hypothesis. Methods and Measures: We hypothesized that individuals with Q-angles more than 15° would display an increase in rearfoot eversion and tibial internal rotation during running. Thirty-two nonimpaired subjects (men: n = 16, mean age = 22 ± 3 years; women: n = 16, mean age = 23 ± 3 years) ran over ground, and 3-dimensional kinematic data were collected from the right lower extremity. Subjects with a Q-angle of 15° or less comprised the low-Q-angle group, whereas those with Q-angles of more than 15° comprised the high-Q-angle group. Segment and joint maximum angles and the times when the maxima occurred during stance were measured. Results: The Q-angle magnitude did not increase the maximum segment or joint angles during running. The groups displayed similar maximum angles for rearfoot eversion (low Q-angle, -15.5 ± 5.0°; high Q-angle, -15.6 ± 6.6°) and tibial internal rotation (low Q-angle, -8.8 ± 4.8°; high Q-angle, -6.8 ± 5.1°). The high-Q-angle group (39.5 ± 16.3%) achieved maximum tibial internal rotation later in the stance phase than the low-Q-angle group (28.8 ± 10.7%). Conclusions: In support of the previous investigations involving Q-angle influences on kinematics, our study did not reveal any differences between groups in maximum joint or segment angles. The kinematic information did reveal that the high-Q-angle group displayed an increase in time to maximum tibial internal rotation. The impact of this single factor on producing knee injury is unknown.

J Orthop Sports Phys Ther. 2000;30(5):271-278.

Key Words: segment alignment, 3-dimensional kinematics, tibial rotation

Due to increasing emphasis on closed kinetic chain exercises in rehabilitation, there is a need to objectively quantify their effectiveness. The purpose of this study was to determine the test-retest reliability of the peak force and total work scores during a concentric isokinetic leg press pattern using the Lido Linea closed kinetic chain isokinetic dynamometer. The static calibration of force measurements was established by hanging a series of certified weights from a lever arm of known length affixed to the system's force measurement shafts. A repeated-trials, multiple-day experimental paradigm was utilized to establish the static calibration procedure's reliability. No significant difference was found between expected and observed force scores (p > .05). Thirty healthy, active subjects (22.5 ± 3.9 years) performed concentric isokinetic leg press exercise under maximal voluntary conditions across a velocity spectrum of 25.4, 50.8, and 76.2 cm/sec (10, 20, and 30 inch/sec) in a test-retest experimental paradigm, separated by 24-72 hours. Intraclass correlation coefficient values (ICC 2,1) across Day 1 and Day 2 for peak force and total work ranged from 0.87 to 0.94 (p < .05). The data indicate that the Lido Linea closed kinetic chain isokinetic dynamometer is an appropriate instrument for assessing concentric isokinetic performance during a closed kinetic chain leg press pattern.

J Orthop Sports Phys Ther. 1997;25(2):133-136.

Key Words: muscle strength, reliability, closed kinetic chain

Plyometric training has become a popular training and rehabilitation tool. The purpose of this study was to compare the effects of plyometric and isokinetic concentric/eccentric training of the shoulder internal rotators. Female subjects (N = 78) were randomly assigned to 3 groups: control, isokinetic training, and plyometric training. Pre-/posttesting measurements included: 1) concentric/eccentric isokinetic power measurements of the shoulder internal rotators at 60°/sec, 180°/sec, and 240°/sec; 2) kinesthetic measurements of shoulder internal rotation, external rotation < 45°, and external rotation > 45°; and 3) a softball distance test. Both groups trained twice a week for 8 weeks. Power and kinesthetic data were analyzed using multiple analyses of variance with repeated measures. A one-way analysis of variance was performed on the softball throw data. No significant (p < .05) pre-/posttest differences were found with kinesthetic testing or the softball throw. Pre-/postpower differences were significantly greater for the isokinetic group at 60°/sec eccentric, 120°/sec concentric and eccentric, and 240°/sec concentric and eccentric. Isokinetic training of the shoulder internal rotators increases isokinetic power, but neither isokinetic nor plyometric training resulted in a functional improvement with the softball throw.

J Orthop Sports Phys Ther. 1996;23(2):125-133.

Key Words: shoulder, resistive exercise, throwing