Knee injuries account for the sports-related increased risk of knee osteoarthritis.

Increased risk of osteoarthritis has been found among athletes active in different kinds of sports. Knee injury is an established risk factor for knee osteoarthritis. In this population-based case-control study we investigated the risk of knee osteoarthritis with respect to sports activity and previous knee injuries. A total of 825 cases with x-ray-verified femorotibial osteoarthritis were identified at six hospitals in southern Sweden. The cases were matched (age, sex and residential area) with 825 controls from the general population. Mailed questionnaire data on sports activity for more than 1 year after the age of 16, knee injuries and confounding variables (weight, height, heredity, smoking and occupation) were collected and analyzed using logistic regression models. The response frequency was 89%. Among men knee osteoarthritis was related to soccer (odds ratio (OR) 1.6, 95% confidence interval (CI) 1.1-2.2), ice hockey (OR 1.9, 95% CI 1.2-3.0) and tennis (OR 2.0, 95% CI 1.1-3.8) but not to track and field sports, cross-country skiing, and orienteering. After adjustment for confounding variables soccer and ice hockey remained significantly related to knee osteoarthritis, but after adjustment for knee injuries no significant relation remained. The sports-related increased risk for knee osteoarthritis was explained by knee injuries.

Knee osteoarthritis and body mass index: a population-based case-control study.

OBJECTIVE: It is well established that overweight is related to osteoarthritis of the knees. The aim of this study was to investigate the risk of knee osteoarthritis for men and women in relation to body mass index (BMI) within the normal weight range and to assess the effect of former versus current weight. METHODS: A population-based case-control study was carried out in the southern part of Sweden, including 825 cases with X-ray verified femorotibial osteoarthritis and 825 age-, sex-, and county-matched population controls. Mailed questionnaire data on weight, height, and confounding factors (heredity, smoking, knee injuries, and physical activity) were collected and analysed using logistic regression models. The response frequency was 89%. RESULTS: Mean age of the participants was 63 years, and 57% were women. The adjusted risk of knee osteoarthritis was increased fourfold in men with a current BMI 23 to < 25 kg/m2 as compared to men with BMI < 23 kg/m2 (OR 4.0, 95% CI 1.7-9.5). The commensurate risk for women was 1.6 (95% CI 0.9-3.1). BMI at 30 years of age was similarly related to knee osteoarthritis. CONCLUSION: A moderate increase in BMI, within the normal weight range, was significantly related to knee osteoarthritis among men. Overweight at any time was related to knee osteoarthritis.

Prothrombin, albumin and immunoglobulin A form covalent complexes with alpha1-microglobulin in human plasma.

Molecules containing the 33-kDa plasma protein alpha1-microglobulin were isolated from human plasma by anti-(alpha1-microglobulin) affinity chromatography. Five major bands could be seen after electrophoretic separation of the alpha1-microglobulin-containing proteins under native conditions. Immunoblotting demonstrated alpha1-microglobulin in all five bands. Two of these have been described previously: free alpha1-microglobulin and alpha1-microglobulin complexed with IgA (IgA x alpha1-microglobulin). The other three bands were identified as prothrombin alpha1-microglobulin, albumin x alpha1-microglobulin and dimeric alpha1-microglobulin. Prothrombin x alpha1-microglobulin were 1:2 and 1:1 complexes which carried approximately 1% of total alpha1-microglobulin, had molecular masses of about 145 kDa and 110 kDa upon SDS/PAGE and dissociated completely to free alpha1-microglobulin and prothrombin (72 kDa) when reducing agents were added, suggesting that the complexes were stabilized by disulfide bonds. The alpha1-microglobulin molecules did not inhibit cleavage of prothrombin by factor Xa and were bound to the peptides which were released upon activation of prothrombin. Albumin x alpha1-microglobulin, corresponding to 7% of total plasma alpha1-microglobulin, was a mixture between 1:1 and 1:2 complexes, with masses upon SDS/PAGE of approximately 100 kDa and 135 kDa, respectively. Both these complexes dissociated only partially to free alpha1-microglobulin and albumin when reducing agents were added. The albumin x alpha1-microglobulin complexes carried a yellow-brown chromophore similar to free alpha1-microglobulin. The complex-binding to alpha1-microglobulin did not block the fatty-acid-binding ability of albumin. The plasma concentrations of albumin x alpha1-microglobulin and prothrombin x alpha1-microglobulin were estimated to 5.2 mg/l and 1.1 mg/l, respectively.