Abstract:

Introduction . Medial compartment knee osteoarthritis (MKOA) is a complex process that is associated with genu varum, quadriceps weakness and medial compartment joint laxity that predisposes one to episodes of instability. The goal for conservative management is to control pain and improve function and health related quality of life. Unloader braces offer a reasonable alternative for pain relief and improved function without the surgical risk of osteotomy. Research suggests instability resulting from substantial frontal plane joint laxity is controlled mechanically via the brace and that a neutral brace alignment may afford the same benefit as valgus correction. Therefore, the purpose of this preliminary study was to ascertain the degree to which valgus unloader knee braces control instability, improve pain relief and function, and influence kinematic and kinetic patterns during gait among patients with MKOA and genu varum.

Methods . Ten patients with moderate to severe MKOA and genu varum were recruited and fitted for a custom GII Select Unloader Brace (OSSUR Americas, Foothill Ranch CA). A cast of the involved limb was taken with the patient in weight-bearing and a brace was fabricated specific to each individual's leg shape and alignment. Skeletal alignment was measured from standing weight bearing radiographs and quadriceps strength was assessed isometrically. Pain, instability and functional status were assessed using the self-report Knee Outcome Survey- Activities of Daily Living Scale (KOS-ADLS) and Knee Osteoarthritis Outcome Score (KOOS). Gait analysis was performed to assess kinematic and kinetic patterns under three conditions, knee unbraced (baseline), followed by two randomized brace settings with the knee in neutral (regular knee alignment) and 4? valgus. A two week washout period separated brace conditions. Data from seven healthy age and gender matched controls were compared. Repeated-measures ANOVA with post hoc pair wise comparisons were used for comparing brace settings. Independent t-tests were used to assess differences between groups. Alpha was set at p < 0.05.

Results . The MKOA group when compared to controls demonstrated significant medial joint space narrowing (mean ? SD: versus 2.8 mm ? 1.7 mm vs. 4.5 mm ? 0.7 mm, p = 0.009;) and malalignment (mean ? SD: 24.2% ? 16.1% vs. 41.4% ? 7.7% p = 0.031). Patients had significant quadriceps strength deficits (p = 0.019). Symptoms, pain, function and knee instability from self-report questionnaires scored worst when unsupported and pain, symptoms, and function scored highest with the neutral brace compared to the valgus but remained lower than healthy controls. Knee flexion excursions (RoM) during weight acceptance were impaired compared to controls in all brace settings (mean ? SD baseline: -9.8 ? 4.4, mean ? SD control: -15.8 ? 3.1; p = .007), but RoM significantly increased with the brace aligned in valgus. A trend towards improved knee stability was observed with neutral alignment affording better results (p = .069). Peak knee adduction moments were unaffected by either brace setting and remained significantly higher compared to controls.

Conclusions . The results from this study are preliminary. Our contention was that pain relief is mediated through improved knee stability rather than "mechanically unloading the medial compartment". Our preliminary results support this notion. Knee instability, if left untreated, might lead to the development of a neuromuscular joint-stabilization strategy that could hasten progression of the disease (1). Continued research is needed to identify whether increased co-contraction leads to higher muscle stiffness or more joint loading, and to understand the long-term effect of altered muscle activity on the progression of OA. The advantages of this study lie with the possibility that positive effects of the neutrally aligned brace may lead to an increase in the utilization of braces for the treatment of osteoarthritis as a method to mediate pain and improve function and instability.