Weight loss is associated with reduced risk of knee and hip replacement: a survival analysis using osteoarthritis Initiative data

Key Points

1. This study demonstrated a positive association between percentage of body weight change from baseline and the risk of knee replacement and hip replacement (in hips that were persistently painful), regardless of baseline BMI.
2. Every 1% weight loss was associated with a 2% reduction in the risk of knee replacement in people with or at risk of clinically significant knee osteoarthritis.
3. Every 1% weight loss was associated with a 3% reduction in the risk of hip replacement in people who had one or more persistently painful hips at baseline.

BACKGROUND & OBJECTIVE

Obesity is an important, modifiable risk factor for the development and progression of knee and hip osteoarthritis (OA) (1). As such, clinical guidelines commonly recommend weight loss in patients with osteoarthritis who are overweight or obese (2,3). However, it is currently unknown whether weight loss reduces the risk of knee or hip replacement in those with comorbid osteoarthritis and obesity.

Therefore, the aim of this study was to describe the association between weight loss and the risk of knee and hip replacement, after considering known risk factors for joint replacement, in an osteoarthritis-specific cohort.

Obesity is an important, modifiable risk factor for the development and progression of knee and hip osteoarthritis.

Care should be taken when advising weight loss in older people (aged >65 years) to ensure the maintenance of lean body mass and bone density.

METHODS

• The authors of this study conducted a time-to-event survival analysis from a population-based cohort of participants who had or were at risk of clinically significant knee osteoarthritis at baseline.

• Data was taken from the Osteoarthritis Initiative (OAI), which collected data from four clinical centres in the United States. The exposure was body weight change from baseline (as a percentage of baseline) at repeated follow-up visits over 8 years.

• The outcome of interest was the incidence of primary knee or hip replacement during the 8-year follow-up.

RESULTS

• A total of 8069 knees from 4081 participants, and 8076 hips from 4064 participants (59.3% female) aged 45-79 years, with a mean body mass index (BMI) of 28.7 kg/m² (standard Deviation (SD): ± 4.8 kg/m²), were included in the knee and hip analyses.

• Participants in the knee and hip datasets had a mean ± SD age of 60.8 ± 9.1 years and 60.7 ± 9.1 years, respectively. There were 423 knee replacements (5.2%) in the knee dataset and 181 hip replacements (2.2%) in the hip dataset.

• Body weight change had a small, positive, linear association with the risk of knee replacement (adjusted hazard ratio (HR) 1.02; 95% confidence interval (CI) 1.00–1.04) and was also positively and linearly associated with the risk of hip replacement only in hips that were persistently painful at baseline (adjusted HR 1.03; 95% CI 1.01–1.05). See Figure 1 for a visual representation of this.

• In other words, every 1% weight loss was associated with a 2% reduced risk of knee replacement in people with or at risk of clinically significant knee OA, and a 3% reduced risk of hip replacement in people who had one or more persistently painful hips at baseline, regardless of baseline BMI.

LIMITATIONS

• This study is an observational study which increases the potential for confounding bias. However, potentially relevant variables in statistical analyses (including socioeconomic factors such as marital status, educational level, income status and employment status) were accounted for to minimize the potential for confounding bias.

• Information on body composition was not available in the OAI datasets. Therefore, it is unclear whether changes in body weight were associated with changes in fat mass and/or lean mass.

CLINICAL IMPLICATIONS

This study demonstrated a positive dose-response association between percent body weight change from baseline and the risk of knee replacement or hip replacement (in hips that were persistently painful), regardless of baseline BMI. More specifically, every 1% weight loss was associated with a 2% reduced risk of knee replacement in people with or at risk of clinically significant knee OA, and a 3% reduced risk of hip replacement in people who had one or more persistently painful hips at baseline.

These results are supported by previous research demonstrating a dose-response relationship in patients with knee OA, whereby a loss of ≥5% of body weight was associated with positive changes in clinical and mechanistic outcomes, and clinically important benefits continued to increase with weight loss of 5-10%, 10-20%, and >20% of body weight (4).

The mechanisms underlying the potential clinical benefits of weight loss in patients with knee and hip OA who are overweight or obese are likely multifactorial. This includes both mechanical (e.g. decreased joint load) and systemic factors (e.g. decreased production and release of cytokines and adipokines by adipose tissue which promote low-grade systemic inflammation) (1). This is in addition to the many other known benefits of weight loss such as reducing the risk of cardiovascular disease, diabetes, etc.

Consequently, clinical guidelines commonly recommend weight loss in patients with OA who are overweight or obese (2,3). Weight loss is typically recommended in individuals presenting with symptomatic OA and a BMI ≥25 kg/m², and weight loss interventions should comprise a combination of dietary advice and exercise (5). However, care should be taken when advising weight loss in older people (aged >65 years) to ensure the maintenance of lean body mass and bone density (5).

+STUDY REFERENCE

Salis Z, Sainsbury A, Keen H, Gallego B, Jin X (2022) Weight loss is associated with reduced risk of knee and hip replacement: a survival analysis using Osteoarthritis Initiative data. International Journal of Obesity, 46(4), 874-884.

SUPPORTING REFERENCE

1. Berenbaum, F., Wallace, I.J., Lieberman, D.E. and Felson, D.T., 2018. Modern-day environmental factors in the pathogenesis of osteoarthritis. Nature Reviews Rheumatology, 14(11), pp.674-681.
2. Kolasinski, S.L., Neogi, T., Hochberg, M.C., Oatis, C., Guyatt, G., Block, J., Callahan, L., Copenhaver, C., Dodge, C., Felson, D. and Gellar, K., 2020. 2019 American College of Rheumatology/Arthritis Foundation guideline for the management of osteoarthritis of the hand, hip, and knee. Arthritis & Rheumatology, 72(2), pp.220-233.
3. The National Institute for Health and Care Excellence, 2014. Osteoarthritis: Care and Management—Clinical Guideline. National Institute for Health and Care Excellence: London, UK.
4. Messier, S.P., Resnik, A.E., Beavers, D.P., Mihalko, S.L., Miller, G.D., Nicklas, B.J., DeVita, P., Hunter, D.J., Lyles, M.F., Eckstein, F. and Guermazi, A., 2018. Intentional weight loss in overweight and obese patients with knee osteoarthritis: is more better? Arthritis care & research, 70(11), pp.1569-1575.
5. Royal Australian College of General Practitioners, 2018. Guideline for the Management of Knee and Hip Osteoarthritis, 2nd ed.; Royal Australian College of General Practitioners: Melbourne, Australia.