Weight Discrimination After Anterior Cruciate Ligament Injury: A Pilot Study

Abstract

Héroux ME, Tremblay F. Weight discrimination after anterior cruciate ligament injury: a pilot study. Objective To determine whether the ability to discriminate weights remained accurate after anterior cruciate ligament (ACL) injury. Design Descriptive case series. Setting Outpatient physical therapy. Participants Convenience sample of 10 participants with unilateral ACL injuries (age, 27.1±8.2y) and 8 healthy controls (age, 22.6±2.8y). Interventions Not applicable. Main Outcome Measures Weber fractions, expressed as percentage differences from the standard weight (3.00kg) that could be reliably detected (75% correct level), were derived from each leg to provide an index of proprioceptive acuity for weight discrimination. Subjective ratings of knee function (Activities of Daily Living Scale of the Knee Outcome Survey) and measurements of quadriceps strength (peak isometric torque). Results The ACL group exhibited a reduced acuity to detect differences in weight on the injured, as compared with the uninjured, side as reflected in the increase in Weber fractions (mean, 6.7%±2.3% vs 4.8%±1.1%, respectively; P=.043). No such difference in acuity between legs was detected in healthy controls (mean right and left, 5.4%±1.4% vs 5.7%±1.3%, respectively, P=.99). Conclusions Proprioceptive acuity for weight discrimination was significantly reduced after an ACL injury, possibly reflecting deficits in the ability to properly calibrate force signals generated while muscles are actively contracting, as a result of a loss in ligamentous sensory innervation.