CLINICAL QUESTION

How much weight loss is needed to improve pain and quality of life for patients with overweight or obesity and knee osteoarthritis (OA)?

EVIDENCE-BASED ANSWER

A total body weight loss of 5.1%, or 0.24% per week, results in clinically significant improvement in pain and disability in patients with overweight or obesity and knee OA. (Strength of Recommendation [SOR]: A, meta-analysis of four randomized controlled trials [RCTs].) Although weight loss improves pain caused by knee OA, there is no known minimum level of weight loss at which pain reduction is expected to occur. Greater weight loss leads to greater pain reduction.

EVIDENCE SUMMARY

A 2007 meta-analysis evaluated the effect of weight change on symptoms associated with knee OA in four RCTs that included 454 patients.¹ The mean body mass index (BMI) levels in the trials were 36, 36, 34, and 29 kg/m², respectively. Inclusion criteria were diagnosis of knee OA, RCT design, specification of comparative treatment, and relevant outcome data.

Two of the RCTs used the self-administered Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) to measure patient pain and disability. The WOMAC subscale for pain includes five items (range = 0–20 total score). The WOMAC subscale for disability asks patients to rate the degree of difficulty in performing activities on a scale from 0 (none) to 4 (extreme). The third RCT used the Fitness and Arthritis in Seniors Trial (FAST) Functional Performance Inventory to measure disability; the fourth study used an unnamed survey to assess pain. Two RCTs used the Lequesne index of severity for osteoarthritis of the hip (LISOH) score to measure severity.