Tests we would like to do for diagnosis: Radiographs: Possible fracture of the femur, tibia and/or fibula Evaluate for avulsion fractures at the point of ligament attachment Evaluate the spatial relationship of the components of the joint capsule for displacement Do a stress radiograph to reproduce possible displacement Evaluate joint for abnormalities to fibrous or ligamentous supporting structures Evaluate for joint malformations or evidence of bone remodeling (osteophyte formation) Evaluate anterior displacement of the tibia in relation to the femoral condyles on Lateral Contrast Radiographs would be beneficial for a more thorough evaluation of the intra-articular structures, such as the articular cartilage and synovium, and evaluation of capsular trauma. Joint tap/fluid analysis: The presence of non-septic inflammatory cells would be consistent with a cranial cruciate rupture. Blood Chemistry: CBC-evidence of systemic infection