Deficits in Quadriceps Strength and Patient-Oriented Outcomes at Return to Activity After ACL Reconstruction: A Review of the Current Literature

Context: Side-to-side quadriceps strength deficits are linked to hazardous lower extremity mechanics and reduced function at a time when individuals are returned to activity after anterior cruciate ligament (ACL) reconstruction. As a result, generalized criteria have emerged in the literature, wherein researchers are recommending that patients be cleared for participation once side-to-side differences in strength are = 10% of the noninjured limb. Similar recommendations exist for patient-oriented outcomes (ie, self-reported function and hop tests), where deficits of < 10% are considered ideal at return to activity. It is unclear how many studies actually achieve these clinically recommended results. Evidence Acquisition: Articles that reported quadriceps strength deficits as compared to the contralateral limb were collected from peer-reviewed sources available on Medline and Web of Science databases (1990 through August 2014). Search terms included the following: anterior cruciate ligament OR ACL AND muscle weakness, anterior cruciate ligament OR ACL AND strength; return-to-activity AND strength; anterior cruciate ligament OR ACL AND quadriceps. Study Design: Clinical review. Level of Evidence: Level 4. Results: Average side-to-side strength deficits at 6 months postreconstruction were 23% +/- 8% (range, 3%-40%), while the average at 12 months postsurgery was found to be 14% +/- 6% (range, 3%-28%). The average deficits in self-reported function at 6 months (mean, 14% +/- 5%) and 12 months postsurgery (mean, 13% +/- 6%) were also found to be > 10%. Performance on hop tests was found to be less than optimal at 6 months postsurgery (mean, 11% +/- 7%), but improved at 12 months postsurgery (mean, 1.3% +/- 2%). Conclusion: This review provides an up-to-date account of the typical deficits in strength and patient-oriented outcomes that exist when formalized physical therapy concludes after ACL reconstruction. Based on the studies included, it seems pertinent that researchers and clinicians continue to investigate interventions capable of improving the recovery of quadriceps strength as well as patient-oriented outcomes as the majority of studies report levels that are well below clinical recommendations.