Strength and endurance deficits in adults with moderate-to-severe hip osteoarthritis, compared to healthy, older adults.

Purpose: This study compares lower limb muscle strength and endurance in adults with hip osteoarthritis, to an age-matched control group.
Methods: Thirteen adults with moderate-to-severe hip osteoarthritis (as graded by the Oxford Hip Score) and fifteen older adults participated. Maximal voluntary isometric contraction of the knee extensors, knee flexors and hip abductors and isotonic endurance of the knee extensors were measured using a dynamometer. Function was assessed using the 30-second chair stand test, the 40 m fast-paced walk test and a stair negotiation test. Data were compared between groups using t -tests.
Results: Participants with hip osteoarthritis demonstrated weakness in the affected limb when compared to the control limb during knee flexion (34%, p  = 0.004) and hip abduction (46%, p  = 0.001). Weakness was also observed in the contralateral knee flexors (31%, p  = 0.01). When compared to the control limb, the knee extensors of the hip osteoarthritis group were exhausted prematurely in the affected (70%, p  = 0.001) and contralateral limb (62%, p  = 0.005). The hip osteoarthritis group took twice as long to stair climb ( p  = 0.002), walked 40% slower, ( p  < 0.001), and had a 35% lower sit-stand performance ( p  < 0.001).
Conclusions: Moderate-to-severe hip osteoarthritis may be characterised by bilateral deficits in lower-limb maximal strength, markedly lower knee extensor endurance and impaired functional performance.Implications for rehabilitationIn addition to bilateral deficits in maximal strength of the hip and knee muscles, moderate-to-severe hip osteoarthritis may be characterised by markedly lower muscular endurance of the knee extensors and impaired functional performance.The endurance capacity of the knee extensors can play an important role in daily function, and thus it is important to consider endurance training principles when prescribing exercise for this patient group.Research studies evaluating exercise programmes underpinned by endurance training principles are required to understand the benefits to patients with hip osteoarthritis, and to inform specific exercise prescription in clinical practice.