Abstract
BackgroundReductions in lower extremity muscle strength, size and quality and increased fat content have been reported in advanced hip osteoarthritis (OA). Whether these differences are also evident at earlier stages of the disease and the extent to which they might develop over time is unclear. The main purpose of this 12-month exploratory prospective study was to compare changes in muscle and fat characteristics in individuals with mild-to-moderate hip OA and healthy controls.MethodsFourteen individuals with mild-to-moderate symptomatic and radiographic hip OA (n = 9 unilateral; n = 5 bilateral), and 15 healthy controls similar in age and sex without symptoms or radiographic hip OA were assessed at baseline and at 12-month follow-up. Maximal voluntary isometric strength of the hip and knee muscle groups was assessed using an isokinetic dynamometer. Lower extremity lean and fat mass were assessed using dual-energy x-ray absorptiometry, and thigh muscle and fat areas and thigh muscle density were assessed using peripheral quantitative computed tomography.ResultsKnee extension (p = 0.01), hip extension (p < 0.01), hip flexion (p = 0.03), and hip abduction (p < 0.01) strength, lower extremity lean mass (p < 0.01), thigh muscle area (p = 0.03), and thigh muscle density (p < 0.01) were significantly lower in hip OA compared to controls. Hip extension (p < 0.05), hip flexion (p = 0.03), and hip abduction (p = 0.03) strength significantly declined over the follow-up period in the hip OA group.ConclusionsPre-existing deficits in hip muscle strength in individuals with mild-to-moderate hip OA were accentuated over 12-months, though no changes in symptoms or joint structure were observed. A longer follow-up period is required to establish whether strength deficits drive clinical and structural decline in these patients. Interventions to prevent or slow declines in strength may be relevant in the management of mild-to-moderate hip OA.
Highlights
Reductions in lower extremity muscle strength, size and quality and increased fat content have been reported in advanced hip osteoarthritis (OA)
All participants were screened through self-reported measures of pain and function (modified Harris Hip Score (HHS) [23]) and radiographic examination
Participants were included in the hip OA group if they had hip pain and/or functional limitations during activities of daily living (HHS ≤ 95; 0 = extreme hip problems, 100 = no hip problems) and a KL grade for their affected hip(s) of 2 or 3 and/or joint space width ≤ 3 mm; unilateral hip OA participants had KL scores of 0 or 1 for their contralateral hip
Summary
Reductions in lower extremity muscle strength, size and quality and increased fat content have been reported in advanced hip osteoarthritis (OA). Whether these differences are evident at earlier stages of the disease and the extent to which they might develop over time is unclear. Individuals with advanced hip OA have lower isometric, concentric and eccentric hip muscle strength than healthy controls [4], which likely underpins the reported reduction in physical function in these patients [5, 6]. The pattern and underlying mechanism of lower limb muscle weakness in earlier stages of the disease, and the extent to which muscle weakness might develop over time is unclear. If atrophic lower limb muscle weakness is a feature of earlier stages of the disease than previously reported [7], early intervention to mitigate these deficits may be warranted
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