The impact of quadriceps femoris strength asymmetry on functional performance at return to sport following anterior cruciate ligament reconstruction.
METHODS
Cross-sectional study.


OBJECTIVE
To investigate the impact of quadriceps femoris (QF) muscle strength asymmetry at the time of return to sport on self-reported function and functional performance of individuals following anterior cruciate ligament reconstruction (ACLR).


BACKGROUND
Evidence-based QF strength guidelines for return-to-sport decision making are lacking. Objective guidelines necessitate understanding the impact of QF strength deficits at the time of return to sport on function and performance.


METHODS
Fifty-five individuals (mean age, 17.3 years) who were cleared for return to sport following primary ACLR (ACLR group) and 35 uninjured individuals (mean age, 17.0 years) in a control group participated in the study. QF strength (maximum voluntary isometric contraction) was assessed, and the quadriceps index (QI) was calculated [(involved strength/uninvolved strength) × 100%]. The ACLR group was further subdivided into 2 groups, based on the QI: high quadriceps (QI of 90% or greater) and low quadriceps (QI of less than 85%). The International Knee Documentation Committee Subjective Knee Evaluation Form score was used to assess self-reported function, and hop tests were used to assess functional performance. Multivariate analysis of variance and hierarchical regression analyses were performed.


RESULTS
The individuals in the ACLR group were weaker, reported worse function, and performed worse on hop tests compared to those in the control group (P<.05). The low-quadriceps group demonstrated worse performance on the hop tests compared to the high-quadriceps group and the control group (P ≤.016). Hop test performance did not differ between the high-quadriceps and control groups (P ≥.14). QF strength predicted performance on the hop tests beyond graft type, presence of meniscus injury, knee pain, and knee symptoms.


CONCLUSIONS
At the time of return to sport, individuals post-ACLR who had weaker QF (QI of less than 85%) demonstrated decreased function, whereas those with minimal QF strength deficits (QI of 90% or greater) demonstrated functional performance similar to uninjured individuals. QF strength deficits predicted hop test performance beyond the influences of graft type, presence of meniscus injury, knee pain, and knee symptoms.
Division of Physical Therapy, School of Health and Rehabilitation Sciences, Ohio State University, Columbus, OH 43210, USA. laura.schmitt@osumc.edu
Laura C
LC
Schmitt
Mark V
MV
Paterno
Timothy E
TE
Hewett
D000293:Adolescent; D059549:Anterior Cruciate Ligament Reconstruction / Q000534:rehabilitation; D054874:Athletic Performance / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D012044:Regression Analysis; D055815:Young Adult