Study finds differences in patellofemoral joint contact forces after ACL reconstruction
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Key takeaways:
- Patients who underwent ACL reconstruction with return to sport clearance exhibited low patellofemoral joint contact force.
- Contralateral and control groups exhibited higher patellofemoral joint contact forces.
Published results showed patients who underwent ACL reconstruction with subsequent return to sport clearance still exhibited low patellofemoral joint contact force during side-step cutting tasks.
Researchers performed a controlled laboratory study on 26 male athletes (mean age of 23.2 years) who underwent ACL reconstruction and received subsequent return to sport clearance and a matched control cohort of 22 male athletes (mean age of 28.3 years). According to the study, participants performed anticipated side-step cutting tasks, while researchers analyzed joint kinematics, muscle forces and patellofemoral joint contact forces with 3D motion capture and a force plate.
Overall, peak patellofemoral joint contact force, as measured in terms of body weight, was 12.7 in the ACL reconstruction group, 18.7 in the contralateral group and 17.1 in the control group. Knee flexion angle at the time of peak patellofemoral joint contact force was 52° in the ACL reconstruction group, 56° in the contralateral group and 57° in the control group. Quadriceps force, as measured in terms of body weight, at the time of peak patellofemoral joint contact force was 10.9 in the ACL reconstruction group, 15.1 in the contralateral group and 13.7 in the control group.
“Despite rehabilitation and subsequent clearance to [return to sport], differences in [patellofemoral joint] contact forces are present after ACL reconstruction,” the researchers wrote in the study. “Current rehabilitation and [return to sport] battery may not be effective and sensitive enough to identify and address these differences,” they concluded.
Perspective
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Jason L. Koh, MD, MBA, FAAOS, FAOA
Argell J. San Jose, BSN, BSc, and colleagues explore patellofemoral joint forces in patients who were recently (1 week) cleared to return to sports after ACL reconstruction. Uniquely, they explored loads during side-step cutting, which is a more demanding activity than walking or straight-ahead jogging activity. They found less patellofemoral load and less knee flexion in the operated leg compared to the contralateral side or unoperated controls and concluded that this might be related to later patellofemoral osteoarthritis, which is common after ACL reconstruction. This lower load is not surprising because the knee that has just met the 90% limb symmetry index is still weaker than the other side. The association of this decreased load with subsequent OA is puzzling because most studies associate articular cartilage damage with excessive loads on the joint. Other authors have identified other risk factors for subsequent OA, such as the loss of range of motion or concomitant meniscal injury, both of which directly increase loads on the joint. Most likely, this decreased load reflects incomplete recovery at the time of testing, and the development of late arthritis is more likely to be related to increased load.
Reference:
Shelbourne KD, et al. Am J Sports Med. 2017;doi:10.1177/0363546517718827.
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