Influence of Biomechanical Factors and Movement Retraining on Patellofemoral Pain, Patellofemoral Joint Reaction Force, and Movement Strategy during Single Limb Landing



Journal Title

Journal ISSN

Volume Title



Patellofemoral pain (PFP) is one of the most common lower extremity injuries sustained by active women. Currently there is no long-term solution for PFP and as a result the likelihood for developing chronic symptoms and perhaps even concomitant pathologies such as patellofemoral joint (PFJ) osteoarthritis is heightened. A commonly accepted theory assumes that PFP occurs as a result of excessive PFJ stress that is caused by an increased patellofemoral joint reaction force (PFJRF). This is theory is consistent with clinical reports of symptom onset and provocation during demanding activities that involve single limb landing (SLL) such as running, jumping, and cutting. Furthermore, during many of these functional activities the PFJRF is greatest during the SLL phase as the quadriceps muscles must contract eccentrically to decelerate the body while minimizing otherwise large impulsive loads caused by ground impact. As such, the potential influence of an altered movement strategy resulting in an increased PFJRF is heightened. Nonetheless, little is known about the relationships between PFP, the PFJRF, and movement biomechanics during SLL. Furthermore, since a person’s movement strategy is arguably the most influential factor regarding the PFJRF, it is conceivable that movement retraining may be effective in optimizing the PFJRF and alleviating symptoms during SLL. This dissertation consisted of two separate studies designed explore and describe the relationships between PFP, PFJRF and self-selected SLL biomechanics and examine the effects of movement retraining on PFP, the PFJRF, and SLL biomechanics in active women. In the first study, 31 active women (23.5 ± 3.8 years) performed five SLL trials using their self-selected movement strategy. The rate of change in PFP across trials, the PFJRF, and SLL biomechanics were measured and recorded. Regression and correlation statistics were used to examine the relationships between these variables. It was found that the rate of change in PFP across the landing trials was significantly associated with the peak PFJRF (r=0.435, p=0.014). The peak PFJRF was significantly associated with the adjusted knee extension moment (AKEM) (r=0.937, p=<0.001) and the knee flexion angle (r=0.860, p=<0.001). The hip extension moment was the only sagittal plane biomechanical variable that was identified as a predictor of the knee flexion angle and the AKEM. In the second study, sixty-one active women (31 PFP, 30 control) underwent movement retraining provided by a physical therapist using sagittal plane kinematic feedback obtained using a clinical motion capture system. The effects of movement retraining on PFP, PFJRF, and movement biomechanics in active women during a SLL (0.25 m) were examined. There was no significant group by condition interaction effects or group main effects observed for any dependent variables. However, condition main effects were observed for several dependent variables. In particular, the movement retraining resulted in reduced PFP intensity (p<0.001, 1.9 to 0.8 pain points) and rate of change (p<0.001, 0.37 to -0.15 pain points/trial) for both groups. These changes were associated with increases of 17.9 N/kg for the peak PFJRF magnitude (p<0.001) of and 144.25 N/kg/sec for the maximum rate of the PFJRF development for both groups from self-selected to retrained SLL. The increase in peak PFJRF appears to have been influenced by increases in the AKEM (p=0.017, 2.2 vs 2.3 Nm/kg) and knee flexion angle (p<0.001, 42.5° vs 59.2°) at the time of peak PFJRF. A reduction in the hip extension moment (p<0.001, 0.8 vs 2.0 Nm/kg) and increases in trunk anterior rotation (p<0.001, 10.7° vs 41.2°) and hip flexion angles (p<0.001, 36.3° vs 66.4°) at the time of peak PFJRF were also associated with these changes. Patellofemoral pain was significantly associated with the PFJRF during SLL in active women. Additionally, changes in knee flexion angle and AKEM which likely influenced the PFJRF were also related to other sagittal plane biomechanical factors both proximal and distal to the knee joint. Therefore, in order to effect a change on the PFJRF via movement retraining, clinicians should consider these additional biomechanical factors. Additionally, clinicians interested in effecting an immediate reduction in PFP during activities involving SLL may consider teaching subjects to utilize increased trunk and hip flexion. However, caution should be used in this regard as this landing strategy also appears to increase the PFJRF rate and magnitude which could compromise PFJ structural integrity over time.



patellofemoral pain, single limb landing, patellofemoral joint reaction force, movement retraining