The joint between the thigh bone and the two lower leg bones is called stifle. It is the quadruped equivalent of the knee in bipeds (i.e., humans).
The cranial cruciate ligament (band of connective or fibrous tissue that connects two bones at a joint) is the ligament that connects the thigh bone with the lower leg bone – it helps to stabilize the stifle joint.
A sudden or progressive failure of the cranial cruciate ligament, which results in partial to complete instability of the stifle joint, is referred to as cranial cruciate ligament disease (also referred to as the anterior cruciate ligament (ACL)). Tearing of the cranial cruciate ligament is known as cranial cruciate rupture. It is the most common cause of rear-leg lameness in dogs and a major cause of degenerative joint disease in the stifle joint.
Symptoms of ACL range from having a hint of lameness to being unable to bear weight on the injured leg to swelling on the inside of the joint. A decrease in muscle mass and weakening of muscles in the rear leg would be an indication that the leg is not being used properly and the muscles are suffering as a result. Progressive and permanent deterioration of joint cartilage will result if the condition is left untreated.
While dogs of all ages, sizes and breeds are at risk, certain breeds are more prone to dog ACL injuries, including Labrador retrievers, poodles, bichon frises, German shepherds, rottweilers, and golden retrievers. Obese animals and those that get occasional strenuous exercise are also at a higher risk of this condition. Additionally, male dogs neutered at younger than five months old may be more likely to develop ACL injuries later in life.
