Few studies have evaluated the biomechanics of the hip after anterior cruciate ligament (ACL) reconstruction. This study evaluated hip flexion muscle strength in ACL reconstructed patients with patellar or hamstring tendon graft use, comparing them with healthy controls.

This randomized, controlled trial included ACL deficient patients undergoing reconstruction. The subjects were randomized to receive ACL reconstruction with patella tendon or hamstring tendon grafts. In addition, 64 healthy, male athletes participated as controls. The patients were progressed to resistance and endurance training the 13th to 24th weeks post-surgery. All patients underwent isokinetic hip muscle flexion strength testing the day before surgery and one year after surgery. Healthy controls were tested at baseline and at the end of the study.

Preoperatively, no significant difference was found in hip flexion strength between the patella tendon and hamstring groups. While hip flexion strength was increased one year after ACL reconstruction, it remained significantly reduced compared with healthy controls. In addition, hip flexion strength was significantly higher in the patella tendon group than in the hamstring group at one-year postoperatively (P<0.001).

This study demonstrates that hip flexion strength of reconstructed anterior cruciate ligament deficient patients is decreased compared to that of controls at one year post-surgery.