Symptoms of CCL Rupture
Lameness in the hind leg is the most common sign of cranial cruciate ligament rupture. The animal may be unable to bear its weight or may limp. Lameness occurs immediately after the injury and may subside after several weeks but is likely to return.
Other symptoms of CCL rupture include the following:
- Crepitus (crackling noise of bones rubbing against each other)
- Decreased range of motion
- Hind leg extended when sitting (sit sign)
- Pain when stifle joint is touched
- Resistance to exercise
- Restricted mobility or extension
- Stiffness after exercise
- Thick, firm feel of joint
- Weight shifted to one side of body when standing
Once the ligament is ruptured, movement of the misaligned joint causes further damage, inflammation, pain, and eventually degenerative joint disease. If the meniscus is torn, a pop or snap may be heard when the animal walks.
Diagnosis includes a clinical examination and medical history (information about lameness and injury). The veterinarian tests the joint's range of motion. The cranial drawer sign is definitive for diagnosing CCL rupture. The veterinarian holds the femur tightly and pulls the tibia forward. If the tibia moves between 3 and 5 mm, there has been a rupture or partial tears. Anesthesia may be necessary to move the limb to the extent needed because pain from a ruptured CCL can be severe, and muscle tension can restrict the motion of the joint.
Imaging Tests to Diagnose CCL Rupture
Radiography (x-ray) may suggest, but cannot confirm, a partial tear or a complete rupture. If partial tears exist, the veterinarian can measure the tibial plateau (the angle created by the femur resting against the tibia) to predict when future rupture is likely. X-rays do not show ligaments or other soft connective tissues, but they can show fractures and signs of degenerative joint disease (bone spurs or irregular bone wear) as well as the presence of excess joint fluid.
Arthroscopy is a minimally invasive procedure performed with a fiber-optic tube. For diagnostic purposes, a microscopic camera attached to the tube is inserted into the joint so that the entire joint and abnormalities of bones or soft tissues can be seen. Surgical tools can also be attached in order to take tissue samples and to perform other procedures. The canine stifle joint is too small to allow stabilization procedures to be performed through arthroscopy. This is the diagnostic tool of choice, but it has limited availability in veterinary medicine at this time.
Testing to Diagnose CCL Rupture
Arthrocentesis or joint tap confirms the presence of degenerative joint disease and inflammation. A needle is inserted into the joint, and fluid is withdrawn and analyzed. A high white blood cell count and an opaque consistency of the fluid indicate inflammation; the presence of pus indicates degenerative joint disease caused by infection.
CCL Rupture Differential Diagnosis
Veterinarians must rule out other conditions with similar symptoms, such as the following:
- Stifle joint sprain or meniscus injury
- Acute arthritis (immune-mediated, Lyme disease)
- Caudal cruciate ligament rupture
- Hip dysplasia
- Myelopathies (disease or disorder of the spinal cord or bone marrow)
- Patellar luxation or fracture