The role of weight and age on knee osteoarthritis

Background: Overweight and age are well recognized risk factors for knee osteoarthritis (KOA). Objectives: To determine the role, as well as the sex difference relationship between weight gain, age and KOA. Methods: 429 patients with KOA(306 females,123 males) and 430 healthy controls (307 females,123 males) attending Shaheed Beheshti outpatient clinic between 1995-2000 entered the study. Diagnosis of KOA was confirmed on the basis of the American College of Rheumatology criteria .Patients and controls were compared regarding to age and body mass index (BMI).Statistical analysis was performed by SAS soft ware using logistic regression analysis to determine the association of KOA with age and weight. Adjusted odds ratio was calculated for both sexes and compared. Findings :The mean age of patients was significantly higher than controls (60 + 11 Vs 55.5 + 11.8 years , P = 0.0001 ). BMI of patients and controls were 27.8 + 8.1 and 24.8 + 5.1 kg/m2 respectively (P=0.0001). BMI was higher in female patients than males ( 28.7 + 8 Vs 25.2 + 4.5 kg/m2 , P = 0.0001 ).The age at onset of KOA in women was lower than men .There was also a significant difference in age distribution between two sexes( P=0.0001).With increasing age the relative risk (RR) of KOA increased in all decades after 50 years in females whereas in male patients increased risk was seen at the sixth and seventh decades. In overweight patients RR of KOA was 3.74 [ 95% confidence interval (CI), 2.57–5.43, P = 0.0001] in females and 2.58 ( 95% CI, 1.41 – 4.76, P = 0.002 ) in males. Conclusion: The above findings indicate a sex difference , in KOA association with age,weight and age distribution.