Do laterally wedged insoles and valgus knee braces really unload the medial compartment of the knee? Results of a RCT

Background: In patients with osteoarthritis (OA) of the medial compartment of the knee, symptom reduction and functional improvement were reported with the valgus unloader knee brace or the laterally wedged insole. These clinical effects are attributed to the mechanical unloading of the diseased compartment. However, the exact working mechanism is not fully understood and remains a subject of discussion. Because no static correction of malalignment was seen in prior studies, another possible explanation for the clinical improvement could be a dynamic alteration, in other words a changed gait pattern. For this reason we performed gait analysis of patients wearing a laterally wedged insole or valgus knee brace. Purpose: The aim of the present study was to evaluate the dynamical biomechanical alterations of patients with medial knee OA treated with a laterally wedged insole or valgus knee brace. Methods: In this prospective trial, we randomized 91 patients with early medial knee OA to a laterally wedged insole or valgus knee brace. At baseline and after 6 months, walking distance, use of pain medication, VAS-pain score, WOMAC-score, complications and compliance were determined. Gait was analyzed with and without wearing of the orthosis at baseline and after 6 weeks. Kinematic data were collected using three infrared cameras and a force plate. Measurements were taken of the knee adduction moment (KAM), ground reaction force (GRF), moment arm (MA), walking speed and toe-out angle. Results: A mean reduction of 3.6% (± 9.6) of the peak KAM and 3.7% (± 12.9) of the MA at baseline (immediately after placement of the device) were observed in the insole group. After 6 weeks a mean reduction of 1.3% (± 9.7) of the peak KAM and no reduction of the MA were measured. No reduction of KAM, MA or GRF was seen in the brace group at baseline and after 6 weeks. Subgroup analysis showed no differences in biomechanical effect for obesity, stage of OA and clinical response to the treatment. Conclusions: Laterally wedged insoles unload the medial compartment only at baseline. No biomechanical alteration was seen after 6 weeks of wearing the insole. Valgus brace therapy did not result in any biomechanical alteration at baseline and after 6 weeks. Based on this study, the clinical effects of insoles and braces cannot be elucidated by a certain dynamical biomechanical effect.