Abstract
Objective: Off-loader knee braces have traditionally focused on redistributing loads away from either the medial or lateral tibiofemoral (TF) compartments. In this article, we study the potential of a novel “tricompartment unloader” (TCU) knee brace intended to simultaneously unload both the patellofemoral (PF) and TF joints during knee flexion. Three different models of the TCU brace are evaluated for their potential to unload the knee joint.Methods: A sagittal plane model of the knee was used to compute PF and TF contact forces, patellar and quadriceps tendon forces, and forces in the anterior and posterior cruciate ligaments during a deep knee bend (DKB) test using motion analysis data from eight participants. Forces were computed for the observed (no brace) and simulated braced conditions. A sensitivity and validity analysis was conducted to determine the valid output range for the model, and Statistical Parameter Mapping was used to quantify the effectual region of the different TCU brace models.Results: PF and TF joint force calculations were valid between ~0 and 100 degrees of flexion. All three simulated brace models significantly (p < 0.001) reduced predicted knee joint loads (by 30–50%) across all structures, at knee flexion angles >~30 degrees during DKB.Conclusions: The TCU brace is predicted to reduce PF and TF knee joint contact loads during weight-bearing activity requiring knee flexion angles between 30 and 100 degrees; this effect may be clinically beneficial for pain reduction or rehabilitation from common knee injuries or joint disorders. Future work is needed to assess the range of possible clinical and prophylactic benefits of the TCU brace.
Highlights
Knee braces are a common conservative treatment option for reducing pain and improving function in people with musculoskeletal injuries and disease (Chew et al, 2007), such as knee osteoarthritis (OA) (Ramsey and Russell, 2009; Petersen et al, 2016; Phillips et al, 2016)
The use of these braces in patients with unicompartmental TF disease is supported by biomechanical (Moyer et al, 2015; Petersen et al, 2016) and clinical studies (Rannou et al, 2010; Mistry et al, 2018), the effectiveness of unicompartment off-loader braces may be limited because the vast majority (>90%) of patients have bicompartmental or tricompartmental disease with patellofemoral (PF) involvement (Duncan et al, 2009; Heekin and Fokin, 2014)
As muscles are the primary contributors to PF and TF joint contact loads that increase during weightbearing flexion (Kuster, 2002; Winby et al, 2009; Sasaki and Neptune, 2010; Trepczynski et al, 2012), reduction in muscle effort should reduce the forces transmitted through the joint structures (Budarick et al, 2020)
Summary
Knee braces are a common conservative treatment option for reducing pain and improving function in people with musculoskeletal injuries and disease (Chew et al, 2007), such as knee osteoarthritis (OA) (Ramsey and Russell, 2009; Petersen et al, 2016; Phillips et al, 2016). Unicompartment off-loader braces are a common style of knee brace designed to reduce pain and progressive degeneration of the osteoarthritic knee by redistributing compressive forces away from the diseased medial or lateral tibiofemoral (TF) compartment via joint realignment (Ramsey et al, 2007; Briem and Ramsey, 2013). There are currently three TCU brace models available from the manufacturer, which provide different levels of assistance across the range of motion of the brace. These brace models are designed for different therapeutic purposes or to meet varying user requirements. As in vivo measurements are generally infeasible, a model is required to quantify these effects
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