Altered knee joint movement after ACL surgery could contribute to early-onset knee osteoarthritis

Some individuals who have had anterior-cruciate-ligament reconstruction (ACLR), the kind of surgery often performed on athletes' knees, may develop early-onset knee osteoarthritis. A new study in the Journal of Orthopaedic Research indicates that altered knee joint movement after ACLR could be a contributing factor. 

The study used a unique dynamic X-ray imaging system to accurately measure knee joint movement during walking in people who had undergone ACLR surgery and those with healthy knees. Compared with healthy controls, ACLR patients had a higher vertical position of the patella and a higher location of articular contact between the patella and the femur. A higher riding patella in the ACLR patients was caused by a longer-than-normal patellar tendon, the structure connecting the patella to the tibia. A surprising finding was that a higher riding patella was observed in both the ACLR knee and the uninjured contralateral knee of the ACLR patients. 

Investigators suspect that a higher riding patella may contribute to the development of knee osteoarthritis by shifting the load bearing areas between the patella and the femur to regions of cartilage unaccustomed to load and leaving previously loaded regions unloaded. 

We don't know whether a longer-than-normal patellar tendon that resulted in a higher riding patella existed prior to the ACL injury or resulted from the ACL injury or ACLR surgery. Further research is needed to determine the cause of a longer-than-normal patellar tendon in individuals who have undergone ACLR surgery."

Marcus G. Pandy, PhD, MEngSc, corresponding author of the University of Melbourne, Australia