Bonnie appears to be affected by a sytemic illness. She only raises her head and wags her tail slowly in greeting the veterinarian. This is atypical behavior for a 6 year old labrador retriever.

Bonnie has a history of being a rather active dog. She goes on morning and evening walks with her owner. Her owner takes her on long walks in the woods on the weekends. Bonnie is not on any medication (i.e. tick preventative) other than heartworm preventative.

Her behavior lead us to believe that she has a systemic illness. Tick borne diseases such as Rocky Mountan spotted fever, hepatozoonosis, and erlichiosis usually demonstrate systemic signs prior to lameness. For instance, hepatozoonosis the dog will demonstrate weight loss and bloody diarrhea prior to a lameness characterized by bone pain and associated with muscle or lumbar pain. Other bacterial diseases may also participate in producing a septic arthrtis but are not evident from the clinical signs.

Bonnie demonstrates clinical signs compatible with Lyme disease. Polyarthritis is the most common clinical sign reported in dogs. The arthritis may be septic or immune-mediated with the presence of the spirochete in the synovium and/or synovial fluid. Systemic signs include anorexia, weight loss, lethargy, lymphadenopathy, and pyrexia but are not always present.

Lameness produced by Borrelia burgdorferi can demonstrate an acute or chronic and progressive onset. Swelling of one or more joints is usually evident as in the case of Bonnie. Bonnie demonstrates joint effusion of the left stifle with distention of the capsule on either side of the straight patellar ligament. The spirochete became localized in the joints following hematogenous spread. Bacterial colonization of the stifle joint resulted in inflammation of the synovial membrane as well as hyperplasia and fibrosis of the synovial membrane. The synovial vasculature became more permeable in response to inflammatory mediators resulting in increased fluid production (or joint effusion). Immune complexes may have also localized in these joints producing immune-mediated arthritis. 

Palpation reveals considerable pain with no evidence of joint instability. The patellas are correctly positioned and normally mobile. The collateral ligaments are intact. Signs may be traced to her exposure to a wooded environment or a tick-infested area. Although lyme disease may explain Bonnie's lameness it does not explain the positive cranial drawer sign on the left hind limb or the upper limits of a normal cranial drawer sign for the right hind leg.

The most accurate diagnostic tests for Borrelia burgdorferi are IFA and ELISA tests. Joint fluid analysis for titers may help establish a diagnosis. A dog with Lyme disease may demonstrate joint fluid with neutrophilic inflammation. Radiographically there is no evidence of degenerative joint disease.