Foot and ankle biomechanics play a role in biomechanical response to lateral wedge insoles

Background Lateral wedge insoles have consistently shown to reduce the external knee adduction moment (EKAM) in medial knee osteoarthritis (OA) patients; although there is evidence that certain patients have a paradoxical increase in EKAM. This may be a key factor in determining clinical response and thus identifying and understanding why these patients increase EKAM is critical for prescribing the correct treatment for these patients. Previous evidence has suggested that foot and ankle biomechanics play a role in reducing EKAM by shifting the centre of foot pressure (COFP) laterally and increasing the valgus orientation of the calcaneus, which shortens the lever arm in respect of the knee, thus reducing the EKAM. To date, patients have been studied irrespective of biomechanical response to lateral wedge insoles. In this study we investigated whether dynamic ankle biomechanics can assist in identifying and explaining why some patients increase EKAM and other decrease EKAM when wearing a lateral wedge.