The influence of surgically-induced weight loss on the knee joint

Background: The causal relationship between obesity and osteoarthritis (OA) of the knee is generally accepted. Weight loss has been shown to reduce the development of OA and improve the radiological parameters of existing disease. However, inducing weight reduction is difficult, and thus the number of patients studied has been small. We wished to determine the effects of surgically-induced weight loss on objective, radiological evidence of OA in the knee joint. Methods: 64 consecutive patients that were referred to the Bariatric Surgical Unit were enrolled in the study. The only exclusion criterion was the prior diagnosis of OA. Knee pain alone did not exclude patients from the study. The study was performed in a prospective manner as a before-after trial. Radiographic data was evaluated by an independent radiologist not involved in the patient care or follow-up. Upright film of the knee was taken prior to surgery and 3 months following surgery. Minimal medial joint space width (JSW) was measured by a digital image computer. In addition, patients were clinically assessed using the American Knee Society Score (AKSS) at these times. Results: 59 of 64 patients were available for follow-up. BMI decreased from 43.4 to 36.9 (P<0.01). The medial joint space increased from 4.6 mm to 5.25 mm (P<0.001). The AKSS improved from 78.5 points (perfect function = 100 points) to 90.69 points (P<0.01). Conclusion: Surgically-induced weight loss is an effective, rapid and dependable means of reversing the radiological signs of early changes associated with OA.