TORONTO – Foot osteoarthritis has been a relatively neglected topic by researchers – but that’s finally changing, Michelle Marshall, PhD, observed at the OARSI 2019 World Congress.
Bruce Jancin/MDedge News
Dr. Michelle Marshall
She was a coinvestigator in the groundbreaking Clinical Assessment of the Foot (CASF), a large prospective study that has brought new insights into the prevalence of foot osteoarthritis (OA), its risk factors, the sizable disease burden, and foot OA’s diverse phenotypes. She shared study highlights at the meeting, which was sponsored by the Osteoarthritis Research Society International.
Elsewhere at OARSI 2019, Lucy S. Gates, PhD, presented the eagerly awaited results of the Chingford 1000 Women Study of the progression pattern of symptomatic radiographic OA of the first metatarsophalangeal joint (MTPJ). With 19 years of follow-up, Chingford is far and away the largest and longest longitudinal study of first MTP joint OA.
The prospective, population-based, observational cohort CASF study was carried out by Dr. Marshall and her coinvestigators at Keele University in Staffordshire, England. They surveyed Staffordshire residents aged 50 and older regarding whether they had experienced foot pain within the last 12 months. Those who answered affirmatively were invited to come in for a more detailed assessment and get weight-bearing x-rays of both feet. Among the 557 symptomatic participants with foot x-rays, the prevalence of radiographic OA of the foot was 16.7%, or roughly one in six – underscoring that it’s a common condition. The first MTP joint was the most commonly affected site, with a prevalence of 7.8%, followed by the second cuneometatarsal joint (CMJ) at 6.8%, the talonavicular joint (TNJ) at 5.2%, the navicular first cuneiform joint (NCJ) at 5.2%, and the first CMJ at 3.9%. Three-quarters of those who had symptomatic radiographic foot OA reported disabling symptoms, an established risk factor for falls (Ann Rheum Dis. 2015 Jan;74[1]:156-63).
With an eye toward identification of potential distinct phenotypes of foot OA, the CASF investigators conducted a separate analysis of those study participants with symptomatic radiographic midfoot OA – that is, OA of the TNJ, NCJ, and/or first or second CMJs, but not the first MTP joint. The prevalence in the Staffordshire population over age 50 with a history of foot pain was 12%. Independent risk factors for midfoot OA included obesity, with an adjusted odds ratio of 2.0; pain in other weight-bearing lower limb joints, with an adjusted odds ratio of 8.5; diabetes, odds ratio of 1.9; and previous foot injury, with an associated 1.6-fold increased risk. Midfoot OA was most prevalent in women older than 75 years; however, contrary to the conventional wisdom, a history of frequently wearing high-heeled shoes posed no increased risk.
The burden associated with midfoot OA was reflected in affected individuals’ frequent use of health care resources: During the past year, 46% of them had consulted their primary care physicians about their foot pain, 48% had been to a podiatrist, and 19% had seen a physical therapist (Arthritis Res Ther. 2015 Jul 13;17:178. doi: 10.1186/s13075-015-0693-3).
In a separate analysis, the investigators compiled additional evidence from CASF pointing to the existence of two phenotypes of foot OA: isolated first MTP OA and polyarticular foot OA, with distinct risk factors and symptom profiles (Arthritis Care Res [Hoboken]. 2016 Feb;68[2]:217-27).
“We found that OA affected both feet significantly more than was expected by chance, and we identified strong symmetrical patterns. This mirrors findings in hand OA and implies involvement of systemic components within a foot,” Dr. Marshall said.