Diagnosis and Causes of Partial Cruciate (CrCL) Ruptures in Dogs 

Hind limb lameness is a very common presenting complaint in clinical practice. Cranial cruciate ligament (CrCL) disease is the cause of lameness in a significant number of those pets. When a patient has an obvious cranial tibial thrust and/or drawer motion on exam, most veterinarians feel comfortable guiding the client towards surgical stabilization and a great long-term outcome. But what about the patient with lameness localized to the knee without obvious instability consistent with a cranial cruciate rupture?

This patient may have a partial cruciate ligament rupture.

The cranial cruciate ligament is comprised of different portions that are taut or lax while the stifle is in different angles of flexion and extension.  The craniomedial band is taut in all angles of the stifle, while the caudolateral band is only taut in extension.  In the clinical patient, this looks like a stifle only having instability in flexion (torn craniomedial band) or no instability (torn caudolateral band).  Patients with partial CrCL ruptures typically have joint effusion and consistent pain when the stifle is extended.  Some patients benefit from sedated palpation of their joints to confirm instability and radiographs to rule out other potential causes. Even patients with a partial tear will have excessive soft tissue opacity in the joint consistent with joint effusion and mild arthritic changes.

The cause of CrCL rupture is still uncertain. Multiple causes have been proposed ranging from conformation, degeneration, trauma, pre-existing synovitis, and trauma.  Whatever the cause of a complete or partial tear, we know the ligament does not healonce torn. Research also suggests the synovial fluid itself, the ligament’s blood supply, and the synovial sheath may all contribute to prevent healing.

Treatment of Partial Cruciate (CrCL) Ruptures in Dogs

The clear majority of medically-managed partial CrCL tear patients experience steadily progressive lameness and muscle atrophy, invariably progressing to more severe lameness when the ligament tears completely, the medial meniscus becomes damaged, or both. In comparison, the surgically-managed patient has less overall muscle loss, less overall lameness, and less overall osteoarthritis. They enter surgery in a better overall plane and therefore enjoy a better short- and long-term recovery. Additionally, surgical stabilization and addressing any meniscal damage offers a better long-term outcome by slowing the process of osteoarthritis sooner.

The use of non-surgical therapies such as laser therapy, acupuncture, rehabilitation, bracing, and prolotherapy to treat cruciate ruptures in dogs are suggested on various forums.  While some of these can be very beneficial for patients post-surgery to maximize their recoveries (for example, rehabilitation, laser, massage, and acupuncture), when used alone or in combination without surgical stabilization, such treatments will not achieve the best possible outcome. Furthermore, prolotherapy (injecting a pro-inflammatory substance like dextrose into the joint) is strongly discouraged as a benefit has not been found in multiple human medicine studies. Thus, our recommendation for best treating partial CrCL tears is surgical intervention.