Prevalence and relevance of antibodies to type-I and -II collagen in synovial fluid of dogs with cranial cruciate ligament damage

Objective-To measure and compare synovial fluid antibody titers to type-I a nd -II collagen in stifle joints with instability caused by complete or par tial cranial cruciate ligament (CCL) rupture and joints with osteoarthrosis secondary to other pathologic changes in dogs. Animais-82 dogs with diseased stifle joints. Procedure-Synovial fluid samples were collected from 7 dogs with clinically normal stifles (control group) and 82 dogs with diseased joints (50 stifle joints with complete rupture of the CCL, 20 with partial damage of the CCL , and 12 joints with radiographic signs of osteoarthritis secondary to othe r arthropathies). Synovial fluid samples were tested for autoantibodies to type-I and -II collagen by an ELlSA. Results-In dogs with complete and partial CCL rupture, synovial fluid antib ody titers to type-I and -II collagen were significantly increased, compare d with control dogs. Forty-eight percent (24/50) of samples from dogs with complete CCL rupture and 35% (7/20) of samples from dogs with partial CCL r upture had antibody titers to type-I collagen that were greater than the me an plus 2 standard deviations of the control group titers. Synovial fluid a ntibody titers to type-II collagen were high in 40% of the dogs with partia l or (8/20) complete (20/50) CCL rupture. Dogs with osteoarthrosis secondar y to other pathologic changes had significantly increased synovial fluid an tibodies to type-I and -II collagen, compared with control dogs. Conclusion-Increases in autoantibodies to collagen in synovial fluid are no t specific for the type of joint disorder. It is unlikely that the anticoll agen antibodies play an active role in the initiation of weakening of the C CL.