Body mass index increase associated with structural changes in knee OA

Both the incidence and structural defects of knee osteoarthritis (OA) can be slowed down by a reduction of the body mass index (BMI). Even a moderate weight loss is beneficial in this respect.

Obesity is a known risk factor for OA and is associated with progression of knee OA. “But what we don’t know is whether weight loss is associated with a decreased incidence of knee OA in men and decreased progression of knee OA in men and women,” Dr Zubeyir Salis explained (University of New South Wales, Australia). Therefore, his study aimed to define the association between change in weight and the incidence and progression of radiographic knee OA [1].

Scores from knee radiographs at baseline and at 4 to 5 years of follow-up were obtained from 3 independent data sets (2 from the USA and 1 from the Netherlands). The exposure of interest was the change in BMI from baseline to 4 to 5 years of follow-up. To investigate the incidence of structural defects of knee OA, the researchers selected a total of 9,732 knees with a Kellgren-Lawrence (KL) grade of 0 (none) or 1 (doubtful) at baseline, named the incidence cohort, and determined the odds of having a KL grade at follow-up of 2 (minimal), 3 (moderate), or 4 (severe). To investigate progression, 6,084 knees were assessed with a KL grade at baseline of 2, 3, or 4 (the progression cohort), and the odds of increasing by 1 or more KL grades at follow-up were determined. “We also looked at the degeneration of individual radiographic features (i.e. joint space narrowing and osteophytes on the femoral and tibial surface) on the medial and lateral sides of the knees in both cohorts,” Dr Salis said. Here, degeneration was defined as an increase by 1 or more Osteoarthritis Research Society International (OARSI) grades.

Included were 4,842 participants in the incidence cohort and 3,216 participants in the progression cohort. Change in BMI was positively associated with both the incidence and progression of knee OA. “The change in BMI was also positively associated with narrowing of joint space on the medial but not the lateral compartment of the knee. However, there was no association between the change in BMI and osteophytes in both compartments,” Dr Salis commented.

These results could have an important public health impact. “We estimated that those who lost 1 BMI unit could reduce the incidence of knee radiographic OA by 13% and the progression of knee OA by 10%,” Dr Salis concluded.

1. Salis Z, et al. Weight loss is associated with reduced incidence and progression of structural defects in knee osteoarthritis. OP0227, EULAR 2022 Congress, 1–4 June, Copenhagen, Denmark.

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Posted on 21 July 202217 May 2024