TOPLINE:

Individuals with knee osteoarthritis (OA) and low muscle mass and/or cardiometabolic comorbidities have worse physical function than those with obesity alone, a cohort study found.

METHODOLOGY:

• Researchers used the Multicenter Osteoarthritis Study to evaluate the effect of distinct obesity subtypes on physical function over 7 years in adults with or at risk for knee OA.
• The 1211 participants (mean age, 61.2 years; 63% women) had a BMI of 30 or more and had knee OA or were at risk at baseline, with body composition measured using dual-energy x-ray absorptiometry.
• Obesity subtypes were defined as: obesity with low muscle mass (OLM; n = 416), obesity with cardiometabolic comorbidities (OCC; n = 200), and uncomplicated obesity (UO; n = 595).
• The primary outcome was self-reported physical function, based on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at baseline, 15 months, 2.5 years, 5 years, and 7 years.
• Secondary outcomes were self-reported knee pain (visual analog scale), quality of life, and physical function based on gait speed (20-meter walk test), chair stand time, and isokinetic quadriceps strength.

TAKEAWAY:

• At baseline, both the OLM and OCC groups had higher WOMAC scores, slower gait speed, longer chair stand times, and lower quadriceps strength than the UO group.
• After 7 years, both the OLM and OCC groups continued to have slower gait speed, poorer quality of life, and worse pain than the UO group.
• Five groups of physical function trajectories were identified over 7 years, with 23.0%, 38.5%, 26.0%, 4.5%, and 8.0% of participants in groups 1-5 (from better physical function to worst function based on WOMAC scores).
• Only group 4 showed improvement in physical function and had the highest rate of arthroplasty.

IN PRACTICE:

“[The study] findings support the consideration of body composition and concurrent comorbidities to provide more comprehensive indication of patients who are likely to have greater impairments in functioning and would merit consideration for targeted intervention to avoid or delay mobility disability and a loss of independence in aging with OA,” the authors wrote.

SOURCE:

This study was led by Kristine Godziuk, PhD, University of California, San Francisco. It was published online on April 20, 2026, in Arthritis Care & Research.

LIMITATIONS:

A subset of the OLM group also had cardiometabolic comorbidities, which may have affected interpretation and generalizability. The study included only participants with BMI ≥ 30 and lacked consensus-recommended measures of low muscle strength, limiting the ability to identify sarcopenic obesity. The comorbidity status relied on self-report, which may have missed undiagnosed cases with poor metabolic health.

DISCLOSURES:

The multicenter OA study was funded by grants from the National Institutes of Health (NIH). One author reported receiving fellowships from Obesity Canada and Alberta Innovates as well as a travel scholarship from the Osteoarthritis Research Society International; another author received NIH funding and disclosed funding from Novartis unrelated to this work. 

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.