The influence of functional knee bracing on the anterior cruciate ligamentstrain biomechanics in weightbearing and nonweightbearing knees

Functional knee braces are commonly prescribed after anterior cruciate liga ment injury or reconstruction; however, their ability to protect the ligame nt, or graft, remains unclear. Our objective was to evaluate the anterior c ruciate ligament strain response in braced and unbraced knees during weight bearing and nonweightbearing in combination with three externally applied l oads: I)anterior-posterior shear forces, 2) internal-external torques, and 3) varus-valgus moments. The Legend brace was tested. All external loads we re applied to the tibia with the knee flexed to 20 degrees. Reproducible da ta were obtained from 11 subjects. For anterior shear loads up to 130 N, th e brace significantly reduced strain values compared with the unbraced knee during nonweightbearing and weightbearing conditions. For internal torques of the tibia (up to 9 N.m), strain in the braced knee was significantly le ss than in the unbraced knee when the knee was nonweightbearing only. The b race did not reduce strain values when the knee was subjected to external t orques (9 N.m) or varus-valgus moments (10 N.m) in weightbearing and nonwei ghtbearing knees. These data indicate that a functional knee brace can prot ect the anterior cruciate ligament during anterior-posterior shear loading in the nonweightbearing and weightbearing knee and during internal torques in the nonweightbearing knee.