The most common serious knee injury in dogs is rupture of the cranial cruciate ligament (CCL), also frequently called the Anterior Cruciate Ligament (ACL). This injury can occur at any age and in any breed, but most frequently occurring in middle aged overweight dogs. The clinical signs of an ACL injury are either a complete non-weight bearing lameness in the case of a complete ACL tear or an intermittent persistent limp that will not completely resolve in the case of a partial ACL tear. Complete or partial tears cause varying degrees of degenerative arthritis because of knee instability. Concurrent with ACL tears, meniscus tears may also occur. The meniscus is a cartilage cushion between the two bones of the knee.
Diagnosis of an ACL tear can be made with thorough manipulation of the knee, sometimes needing sedation for complete relaxation to get the best evaluation. The classic abnormal instability motion is called a drawer motion and anterior tibial thrust. Radiographs may also be used to lend to the ACL tear diagnosis. Untreated ACL tears lead to persistent lameness because of instability and pain. Eventually, degenerative arthritis can lead to crippling lameness.
Surgical correction of ACL tears leads to the best return of function and minimizes long-term arthritis. It also allows visualization and removal of a torn meniscus, which also leads to pain and discomfort.
Recent advancement of knee function analysis has allowed for development of better procedures for surgical repair of ACL tears. The most recent advancement in ACL repair is a procedure called Tibial Tuberosity Advancement or TTA. This procedure involves cutting the lower bone of the knee, called the tibia, and implanting a titanium advancement cage to realign the knee to remove the shear forces that the ACL counteracts. The cut bone is then repaired with a titanium plate and bone graft. Healing time is about 8-12 weeks. With the newer approaches to ACL repair, long term return to normal function has been excellent.
Preventive care to alleviate the other ACL from tearing and in many cases to help prevent initial ACL injuries is important. Weight control through diet and a regular controlled exercise program to maintain good muscle strength and avoidance of those weekend warrior runs also play an important role. Unfortunately some breeds are more susceptible to ACL tears than others.