Patellofemoral Joint Loads During Running at the Time of Return to Sport in Elite Athletes With ACL Reconstruction.

BACKGROUND: Patellofemoral joint pain and degeneration are common in patients who undergo anterior cruciate ligament reconstruction (ACLR). The presence of patellofemoral joint pain significantly affects the patient's ability to continue sport participation and may even affect participation in activities of daily living. The mechanisms behind patellofemoral joint pain and degeneration are unclear, but previous research has identified altered patellofemoral joint loading in individuals with patellofemoral joint pain when running. It is unclear whether this process occurs after ACLR.

PURPOSE: To assess the patellofemoral joint stresses during running in ACLR knees and compare the findings to the noninjured knee and matched control knees.

STUDY DESIGN: Controlled laboratory study.

METHODS: Thirty-four elite sports practitioners who had undergone ACLR and 34 age- and sex-matched controls participated in the study. The participants' running gait was assessed via 3D motion capture, and knee loads and forces were calculated by use of inverse dynamics.

RESULTS: A significance difference was found in knee extensor moment, knee flexion angles, patellofemoral contact force (about 23% greater), and patellofemoral contact pressure (about 27% greater) between the ACLR and the noninjured limb ( P ≤ .04) and between the ACLR and the control limb ( P ≤ .04); no significant differences were found between the noninjured and control limbs ( P ≥ .44).

CONCLUSION: Significantly greater levels of patellofemoral joint stress and load were found in the ACLR knee compared with the noninjured and control knees.

CLINICAL RELEVANCE: Altered levels of patellofemoral stress in the ACLR knee during running may predispose individuals to patellofemoral joint pain.