The effect of pain on hip and knee kinematics during running in females with chronic patellofemoral pain

Purpose: Despite the growing recognition of the role of abnormal hip and knee mechanics in patellofemoral pain (PFP), few studies have assessed if or how these mechanics change when the person experiences pain while running. Therefore, the purpose of this study was to determine if the development of pain while running resulted in altered hip and knee kinematics in female runners with PFP as compared to healthy female runners. Methods: Thirty female runners (15 PFP, 15 controls) participated in an instrumented gait analysis while running for 30. min at a self-selected pace. Pain and fatigue were recorded every minute while participants ran. Variables of interest included peak hip adduction, hip internal rotation, knee abduction, knee external rotation, pain, and fatigue. Results: There were significant group by pain interactions for hip adduction (p<. 0.01) and hip internal rotation (p<. 0.01). The healthy group, who did not develop pain had significant increases in both motions compared to the PFP group, who did develop pain. There was also a trend toward less knee external rotation in the PFP group in presence of pain (p=. 0.059). No differences were found for knee abduction (p=. 0.32). A group main effect was found for hip internal rotation (p=. 0.008) in which the PFP group had significantly larger values. Conclusion: Runners with PFP did not alter their hip mechanics over the course of the run. This may have resulted in repetitive stress to the same aspect of the patellofemoral joint and contributed to the initial development of pain. However, the PFP group did attempt to make a compensation once in pain by reducing knee external rotation.