In a recent post it was highlighted that being overweight was a risk factor for osteoarthritis of the knee. The most common way to measure obesity is Body Mass Index (BMI) which is weight in kilogrammes divided by height in meters squared. The World Health Organisation classifies a BMI of 18.5-24.5 as normal, 25-29.9 as overweight, 30 – 40 as obese, 40+ morbidly obese and 50+ as super obese. Bariatric surgery has been suggested to provide benefit for obese patients with hip and knee pain associated with OA. International guidelines suggest this intervention should be used only in patients who fail non-surgical intervention and have a BMI of 40+, or BMI over 35 with medical complications. This review explored the effects of bariatric surgery on patients below this threshold with a BMI greater than 30.
Here’s what they did
Following PRISMA guidelines, the authors searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE and TRIP, BIOSIS-Previews databases for studies assessing the influence of surgically induced weight loss on knee complaints in obese adults with BMI > 30. The intervention of interest was bariatric surgery including gastric bypass, banding gastroplasty and sleeve gastroscopy. Studies involving lipectomy, liposuction or patients with total knee replacement were excluded. Primary outcome was change in knee pain with stiffness, physical function and range or motion as secondary outcomes.
Here’s what they found
Thirteen studies involving 3,837 participants were included in the review; 2,286 underwent bariatric surgery and 1,551 were treated non-surgically. In those studies reporting characteristics of participants, mean baseline BMI was 42.0kgm2, mean age 46.8 years and 72% were female. Only two studies used a control group, and the quality of evidence ranged from very low to moderate (one study only). A variety of outcome measures were used, preventing meta-analysis, but an overall significant improvement was seen in 73% of assessments.
- Four studies measured knee pain intensity and reported a clinically relevant significant decrease
- All five measuring knee physical function reported significant improvement
- Four studies measuring knee stiffness also reported significant improvement
The authors concluded
Bariatric surgery with subsequent marked weight loss is likely to improve knee complaints, such as knee pain, physical function and stiffness, in (morbidly) obese adult patients.
The Musculoskeletal Elf’s view
Bariatric surgery is a major undertaking with risks including general anaesthetics, infections, and blood clots. The authors of this review noted that the quality of included studies was very or too low, making balancing the risks and benefits of this intervention difficult. Other limitations include the short follow up period (3 months) and that studies did not report whether the effectiveness of surgery was related to the severity of osteoarthritis.
What do you think?
What experience have you had of bariatric surgery?
Do you think this is a cost effective way of managing knee pain?