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Thomas W. Kernozek, Naghmeh Gheidi, Matthew Zellmer, Jordan Hove, Becky L. Heinert, and Michael R. Torry

Context: Squatting is a common rehabilitation training exercise for patellofemoral pain syndrome (PFPS). Patellofemoral joint stress (PFJS) during squatting with more anterior knee displacement has not been systematically investigated. Objective: To compare PFJS during squatting using 2 techniques: squat while keeping the knees behind the toes (SBT) and squat while allowing the knees to go past the toes (SPT). Setting: University research laboratory. Participants: Twenty-five healthy females (age: 22.69 (0.74) y; height: 169.39 (6.44) cm; mass: 61.55 (9.74) kg) participated. Main Outcome Measures: Three-dimensional kinematic and kinetic data were collected at 180 and 1800 Hz, respectively. A musculoskeletal model was used to calculate muscle forces through static optimization. These muscle forces were used in a patellofemoral joint model to estimate PFJS. Results: The magnitudes of PFJS, reaction force, and quadriceps force were higher (P < .001) during SPT compared with the SBT technique. Knee flexion, hip flexion, and ankle dorsiflexion angles were reduced when using the SBT technique. Conclusions: Findings provide some general support for minimizing forward knee translation during squats for patients that may have patellofemoral pain syndrome.

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Becky L. Heinert, Thomas W. Kernozek, John F. Greany, and Dennis C. Fater


To determine if females with hip abductor weakness are more likely to demonstrate greater knee abduction during the stance phase of running than a strong hip abductor group.

Study Design:

Observational prospective study design.


University biomechanics laboratory.


15 females with weak hip abductors and 15 females with strong hip abductors.

Main Outcome Measures:

Group differences in lower extremity kinematics were analyzed using repeated measures ANOVA with one between factor of group and one within factor of position with a significance value of P < .05.


The subjects with weak hip abductors demonstrated greater knee abduction during the stance phase of treadmill running than the strong group (P < .05). No other significant differences were found in the sagittal or frontal plane measurements of the hip, knee, or pelvis.


Hip abductor weakness may influence knee abduction during the stance phase of running.