Background/Purpose: There are few studies of hip osteoarthritis (OA) in the United States and none in the last 35 years that have addressed the prevalence of hip OA in an urban population. Recent estimates from Europe suggest that 2-5% of the population age 50 and over has symptomatic hip OA. Our goal was to assess the prevalence of radiographic and symptomatic hip OA within the Framingham Osteoarthritis cohort.

Methods: We studied the Community sample of the Framingham Osteoarthritis study which was recruited  among those 50-79 years using random digit dialing from the town of Framingham in 2002-2005. As part of this examination standing long-limb radiographs of the lower extremities including the pelvis were obtained using a near horizontal beam. In addition, subjects answered questions regarding the presence and frequency of joint symptoms and indicated on a homunculus whether they had hip joint pain on most days of the previous month.  Two reviewers who received training from an expert musculoskeletal radiologist read all films and verified abnormal ones with the radiologist. Films where both hips were unreadable were excluded. Films were also assessed for Kellgren-Lawrence grade: radiographic OA (ROA) was defined as K/L ≥ 2 (probable joint space narrowing plus an osteophyte ≥ 2). Interobserver kappas were 0.72 between the readers. Persons with a hip replacement were defined as having hip OA in that joint (n=22 subjects). Symptomatic hip OA (SxOA) was defined as radiographic OA with ipsilateral hip pain.

Results: Of 1025 subjects with radiographs, 949 films could be evaluated in both hips. Mean age was 63.5 years (sd 9.0), 56% were women, mean BMI was 27.9 (sd 4.6), 98.1% were white.  16.9% had radiographic hip OA (20.8% of men, 13.8% of women). Of those with ROA, 73.1% were unilateral and 26.9% bilateral. 11.7% of subjects under 65 had ROA (67/571) as compared to 24.7% of subjects 65 and over (93/376). In subjects with BMI < 25, 19.3% (53/276) had ROA; for BMI 25-29.9, 16.3% (66/404) had ROA; for BMI ≥ 30, 15.2% (41/269) had ROA. Both whites and non-whites had similar rates of ROA (16.9%). Of those with ROA, 21.9% had hip joint pain, yielding a SxOA prevalence of  3.7% of the total population (4.3% of men, 3.2% of women).

Conclusion: Around 1/6 of the subjects in this population-based cohort had radiographic evidence of hip OA; 3.7% of men and women had symptomatic OA, an estimate similar to studies from Europe.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-radiographic-and-symptomatic-hip-osteoarthritis-in-an-urban-us-population-the-framingham-osteoarthritis-study/