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Knee Flexion Weak After ACL Repair

A popular method used to repair anterior cruciate ligament (ACL) tears is the hamstrings tendon graft. Specifically, a piece of the semitendinosus-gracilis (STG) portion of the hamstrings is used to replace the ACL. The hamstrings help flex (bend) the knee. In this study, knee flexion strength is measured two years after the ACL repair.

Earlier studies have shown that knee flexor strength is reduced for the first month after surgery. More recently other studies have shown longer-term weakness related to STG tendon harvest. In this study twenty (20) patients of one knee surgeon were included. Joint motion, function, sensation, and joint laxity (looseness) were measured after surgery.

Patients were tested in the prone (face down) position to allow as much knee flexion as possible. Joint range of motion and muscle strength were measured. The results showed loss of motion and decreased flexor strength two years after ACL reconstruction with an STG graft. The patients' perception of normal sensation seemed to be linked with function.

Although the STG graft avoids the problems of quadriceps tendon grafts, they do have their own down side. This study confirms the findings of other reports that flexor strength is impaired after ACL repair with an ATG autograft. More study is needed to find the best rehab strategy to regain full strength and use of the hamstrings.

References: Brian S. Elmlinger, MD, et al. Knee Flexor Function 2 Years After Anterior Cruciate Ligament Reconstruction With Semitendinosus-Gracilis Autografts. In The Journal of Arthroscopic and Related Surgery. June 2006. Vol. 22. No. 6. Pp. 650-655.

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