Hamstrings and Quadriceps Weaknesses Following Anterior Cruciate Ligament Reconstruction Persist Up to 6 Months After Return-to-Sport: An Angle-specific Strength Analysis.

Abstract

Background: Hamstrings and quadriceps strength recovery and restoration of the hamstrings-to-quadriceps ratio (H/Q ratio) is a major concern after anterior cruciate ligament reconstruction (ACLR). Recently, moment-angle profiles and angle-specific H/Q ratios are receiving increasing interest.

Purpose: The first objective of this study was to investigate moment-angle profiles and angle-specific H/Q ratio profiles in athletes with ACLR at the time of RTS. The second objective of this study was to assess whether strength asymmetries identified at the time of RTS, persist after six months.

Study design: Case-Control study.

Methods: Twenty athletes who had undergone ACLR performed isokinetic strength tests for concentric knee flexion and extension (60°/s) at RTS, and three and six months later. Twenty controls were tested once. T-tests were used to compare strength differences between 1) ACLR athletes and controls and 2) the injured and uninjured leg of the ACLR athletes. Finally, to assess strength deficits over time, two-way ANOVAs were used.

Results: Angle-specific analyses and peak moments showed lower hamstrings strength in the injured leg of ACLR athletes compared to their uninjured leg at RTS. Furthermore, angle-specific analyses showed a lower hamstrings strength and H/Q ratio in the injured leg compared to controls at larger knee flexion angles. The latter deficit was not identified with a peak-based analysis. The asymmetries identified at RTS did not change over the six months following RTS.

Conclusions: Athletes with ACLR show strength deficits and asymmetries that persist even six months after RTS. As some asymmetries may go undetected by peak-based analyses, angle-specific analyses are recommended.

Level of evidence: Level 3b.