Explosive and maximal strength before and 6 months after total hip arthroplasty

Patients with unilateral hip osteoarthritis experience impairments in lower limb muscle function due to pain and disuse of the affected limb. The influence of hip osteoarthritis and subsequent total hip arthroplasty (THA) has mostly been evaluated by maximal strength tests, yet the functionally important explosive strength capabilities of hip and knee muscles are largely unknown. We aimed to evaluate hip and knee explosive and maximal strength in hip osteoarthritis patients before and after THA. Twenty-one patients with unilateral hip osteoarthritis were evaluated before and 6 months after THA. They performed rapid maximal contractions of hip (flexor, extensor, abductor, adductor) and knee (flexor, extensor) muscles, from which explosive and maximal strength asymmetries were evaluated (involved versus uninvolved limb). Before THA, the involved limb showed significantly lower hip flexor, extensor, adductor, and knee extensor explosive and maximal strength compared to the uninvolved limb. Six months after THA surgery, hip flexor, extensor and adductor maximal and explosive strength asymmetries persisted, except for knee extensors. Explosive, but not maximal strength of hip abductors and knee extensors was lower in the involved limb before surgery and the reduced explosive strength capabilities may compromise daily living activities in hip osteoarthritis patients. After hip replacement, explosive strength asymmetries of knee extensors resolved, yet lingering asymmetries in hip flexor muscles should receive focused attention during postoperative rehabilitation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:425-431, 2018.