The effect of lateral wedge insoles in patients with medial compartment knee osteoarthritis: balancing biomechanics with pain neuroscience

Results on the effects of lateral wedge insoles (LWIs) in patients with medial knee osteoarthritis (OA) are ambiguous and not fully understood. Because of the low cost of this intervention and its clinical utility, attention to LWIs is worth considering. Current insights on the efficacy of LWIs are mainly focused on changing biomechanical aspects, such as the external knee adduction moment, in an attempt to influence pain, functional ability and structural progression. It is however appropriate to interpret the effectiveness of LWIs in a broader concept than the pure biomechanical approach. Given our current understanding of OA-related pain, including the involvement of the central nervous system and nociception-motor interactions, concepts of pain neuroscience should be taken into account. The purpose of this review is to summarize the current state of knowledge regarding the biomechanical effect of LWIs. It aims to discuss the degree to which such biomechanical effect translates to clinical effects (symptom relief, function recovery and reduction of structural progression). In order to explain these clinical effects, this paper balances biomechanics with pain neuroscience. A literature search was performed and reviewed using a narrative approach. Many studies investigated the effect of LWIs on dynamic knee joint loading, and beneficial biomechanical effects (reduction in knee adduction moment) were observed in patients with mild to moderate medial knee OA, in particular when using full-length LWIs. However, despite beneficial biomechanical effects, there is insufficient evidence for clinically important effects or significant reductions in disease progression. Evaluating the effects of LWIs, our current understanding of OA pain should be taken into account, as LWIs may be part of a comprehensive biopsychosocial treatment. Future work on all of the variables that could influence clinical outcomes in order to decide in which subgroups of patients LWIs are (most) effective is necessary.