Knee Stability Controlled by Hamstrings and Functional Knee Brace

Abstract

The purpose of this study was to determine the effectiveness of an off-the-shelf functional knee brace on preventing anterior tibial translation in anterior cruciate ligament-deficient knees (ACL-d) with greater than 6 mm of side-to-side difference, and the effect of a 50% maximal voluntary hamstring contraction on knee joint laxity. A therapist experienced in using the Knee Signature System (KSS) screened 14 patients who had been diagnosed arthroscopically with ACL deficiency. Nine patients (8 men, 1 woman; mean age, 32.9 years; mean mass, 75 kg; mean height, 177 cm) met the inclusion criteria. All participants were 240 ± 42 days post injury. Participants in the study were tested with no brace, with brace, and 50% maximal voluntary contraction (MVC) of the hamstrings. The uninjured limb was tested only in the unbraced condition. Repeated measures ANOVA (p ≤ .05) and a Bonferroni post hoc analysis was used to detect specific differences between conditions. Results indicate that a 50% hamstring contraction provided better control of anterior tibial displacement than a functional knee brace under the same loading conditions, but a brace may contribute significantly to reducing anterior displacement when the hamstring force is not sufficient.