Tribological study of joint pathology

Osteoarthritis (OA) is the most common among the numerous forms of arthritides, affecting millions of people worldwide. Low-grade synovitis is an inflammatory condition commonly seen in OA. In joint fluids aspirated from patients with low-grade synovitis, increased numbers of white blood cells have been detected. During periods of prolonged inflammation, these cells may lyse, releasing lysate into the synovial fluid. The effect of this lysate on cartilage wear and damage has not been investigated previously. A lysate of bovine white blood cells was added to normal bovine synovial fluid. Both lysate treated and normal synovial fluids were used in in vitro tribological wear tests to determine the effect of the white blood cell lysate on the wear and damage of articular cartilage. Cartilage wear increased by a factor of 2.6 when normal synovial fluid was treated with white blood cell lysate. Histology showed considerable damage and fibrillation of the lysate-treated cases, in addition to a loss of proteoglycans in the deep layer of the cartilage. The untreated control cases showed no significant damage or histological abnormalities. It is suspected that the wear and damage seen in the lysate-treated cases is partially due to enzymatic activity within the cartilage. The results of this study suggest that the products of joint inflammation, or synovitis, may have an adverse effect on cartilage wear and damage.