The Role of Experimentally Induced Hip Abductor Muscle Strength Deficits on Frontal Plane Biomechanics during Gait

Knee osteoarthritis (OA) is one of the most common joint diseases, with the majority of OA related changes being observed in the medial tibiofemoral compartment. Biomechanical changes in gait have been observed in patients with medial compartment knee OA (MC-KOA). In particular, the external knee adduction moment (KAM) has been linked with the presence, severity and progression of MC-KOA [1, 2]. It has been speculated that muscular strength of the hip abductors plays an important role in the progression of MC-KOA [1,3]. Indeed, greater internal hip adduction moments during gait have been associated with a reduced likelihood of MCKOA progression [3]. The link between reduced hip abductor function and knee joint loading during gait was recently explored by injecting a pain-inducing solution into the gluteus medius [4]. Although the injection was successful in reducing hip abductor muscular activation, it resulted in an unexpected drop in the KAM. However, it remains unclear whether the gait adaptations observed post-injection were simply an antalgic gait response to pain. An alternative method to reduce the force output of muscles is to perform a nerve block injection. This has the advantage of not inducing pain-related gait adaptations. Therefore, this study aimed to reduce hip abductor muscular strength in healthy subjects via a nerve block injection and observe subsequent alterations in gait. Specifically, it was hypothesised that the external KAM would be greater following the nerve block procedure. A secondary hypothesis was that alterations in hip adduction moment along with contralateral pelvic drop hip adduction angles would also be observed.