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Knee News

Patellofemoral Joint After ACL Reconstruction

Surgery to reconstruct a ruptured or deficient anterior cruciate ligament (ACL) may affect the placement and movement of the patellofemoral joint (PFJ). The patellofemoral joint is where the patella (kneecap) moves against the femur (thigh bone). Whether there is a change in patellofemoral kinematics (motion) after ACL reconstruction remains unknown at this time.

In this study, special computerized MRIs were used to create a three-dimensional (3D) view of the knee joint. Contours of the bone and cartilage surfaces were mapped out for the knee. This information was used to analyze patellofemoral kinematics.

Eight patients were included in the study. All were treated for ACL deficiency by one orthopedic surgeon. A bone-patellar-bone autograft was used in all cases. The author described the specific surgical technique used.

Another type of imaging method called fluoroscopy was used to view the knee position and angle during single-leg forward lunges on the involved side. The same information was gathered on the normal, healthy knee in each patient. Images were imported into a software program.

The position and angles of the knee helped identify the patellar tendon kinematics. Patellar flexion, rotation, tilt, and shift were viewed and compared from normal to operative side.

They found that reconstruction of the ACL did not restore the normal function of the patellofemoral joint. Changes in patellar tracking and patellofemoral cartilage contact points altered the normal function of the joint.

ACL reconstruction restores knee joint stability. It even improves patellofemoral joint function. But it doesn't completely restore normal patellofemoral kinematics. This means there could be uneven wear patterns that lead to degenerative changes in the knee.

These findings may explain why some patients with a bone-patellar tendon-bone graft report patellofemoral pain after surgery using this type of tendon graft.

Samuel K. Van de Velde, MD, et al. The Effect of Anterior Cruciate Ligament Deficiency and Reconstruction on the Patellofemoral Joint. In The American Journal of Sports Medicine. June 2008. Vol. 36. No. 6. Pp. 1150-1159.


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