Anterior cruciate ligament strain and tensile forces for weight-bearing and non-weight-bearing exercises - Part 1
ACL surgical reconstructions are followed by 4 to 9 months of rehabilitation, during which the knee may be loaded cautiously to protect the fixation sites and healing/maturing graft, while improving range of motion, strength and dynamic stability. Consolidation of bony fixation sites in the tibia and femur may take up to 12 weeks, while the graft itself weakens during the first 4 weeks, and takes several weeks to revascularise and mature. By inducing antero-posterior translations of the tibia at different knee angles, quadriceps and hamstrings activity balance can modulate the strain on the ACL graft. This article reviews the strains and forces applied to the ACL during non-weight-bearing (NWB) and weight-bearing (WB) exercises.
- Seated Knee Extension. Peak ACL loading usually occurs at 10-30° of knee flexion, and adding an external resistance distally also increases the loading. Because minimal ACL loading occurs at higher angles, it is recommended to perform this exercise between 50-100°, eventually with a resistance proximal to the knee.
- Seated Knee Flexion exercises produce virtually no ACL loading; they however stimulate the hamstrings donor site, which may need 6-8 weeks to heal.
The second part will address WB exercises used during rehabilitation of ACL reconstructions. > From: Escamilla et al., J Orthop Sports Phys Ther 42 (2012) 208-220. All rights reserved to the Journal of Orthopaedic & Sports Physical Therapy.
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