Cruciate Disease

Stretching, Tears and Rupture of the Cruciate Ligament

The canine stifle (knee) is a complicated joint. It has the same anatomical features as the human knee joint, but functionally there is a significant difference. In people, maximum weight-bearing occurs with the knee held straight, whereas in the dog maximum weight-bearing occurs with significant flexion of the joint. This difference exaggerates the stress applied to the cranial cruciate ligament, the main subject of this discussion.

The stifle consists of the femur above, the tibia below, the patella (kneecap) in front and two small bones called fabellae behind the lower part of the femur. The menisci are wedges of cartilage acting as cushions within the joint. A variety of ligaments binds the structure together, allowing for smooth functioning and even wear and tear.

The paired cruciate ligaments within the stifle joint are vital for preventing back-and-forward movement of the femur and tibia relative to one another.

Location of the stifle joint on a dog Healthy ligament Ruptured ligament

Disease, including partial and complete rupture of the cranial cruciate ligament (CCL, so named because it attaches at the front of the tibial plateau) is probably the most common orthopaedic disease of dogs.

Cruciate disease history usually involves a sudden-onset lameness of a hind leg with markedly reduced or lack of weight-bearing. Untreated, this improves over a week or so, but is easily re- injured with activity. Progressive, intermittent lameness following the acute injury is the most common scenario we see.

At examination the dog may have pain and swelling in the stifle joint. Definitive diagnosis of cranial cruciate ligament rupture relies on demonstration of something called the cranial drawer sign. To do this the veterinarian stabilizes the femur just above the joint with one hand, and attempts to push the top of the tibia forward with the other hand. If the tibia moves forward distinctly (like a drawer being opened), complete CCL rupture is confirmed. Diagram of movement performed by veterinarian to confirm CCL rupture.

Absence of a drawer sign in no way entirely rules out cruciate disease. Partial rupture, splinting of the stifle by swelling and muscle bulk in large dogs and other factors, can all disguise underlying CCL disease.

Thickening of the inside aspect of the stifle joint in longer-standing cases, x-ray demonstration of arthritic changes, and demonstration of the drawer sign with the patient sedated, are other issues that support a diagnosis of CCL disease.

What causes cruciate ligament rupture?

A range of situations can occur. Commonly a young, athletic dog playing vigorously subjects their ligaments to unbearable strain. This presents as sudden lameness in young large-breed dogs. Just as commonly, middle-aged to older dogs (often overweight) have weakened ligaments, with stretching, partial tears and then complete rupture. The ongoing partial injuries may not be noticed, or ignored, until the complete rupture occurs. This can happen suddenly with normal activity. A significant number of these dogs are also likely to rupture their second cruciate ligament.

There is very likely a genetic susceptibility to CCL disease, with some dogs more prone due to the biomechanical design of their stifles.

The consequence of a ruptured CCL is stifle instability, with rapid onset of damage to the joint cartilage and menisci and the progressive development of the degenerative joint disease known as osteoarthritis. Early, vigorous attempts to stabilize the joint and halt the degenerative process are very important.

Treatments

Some small breed dogs (and most cats) can be treated conservatively (non-surgically). This involves very careful, strictly supervised cage-confinement for about six to eight weeks. During this time, restriction of weight-bearing allows the other tissues around the stifle joint to take up the slack resulting from loss of the CCL. Chondroprotective and anti-inflammatory drugs are given to protect joint function and for comfort. Rehabilitation exercises are started in the latter part of the confinement period. Success rates with this form of treatment are variable, mainly depending on the degree of compliance with confinement and the temperament of the patient. The case of the busy, time-poor client with a very active dog is probably better managed surgically from the start. In all surgical cases the stifle joint is opened and inspected. The torn cruciate ligament and any damaged portions of meniscal cartilage are removed. This is a very important part of any surgical procedure for cruciate disease. All surgical procedures require some post-surgical exercise restriction, but room-confinement initially is usually adequate.

All surgical cases must also have had standard x-ray studies and examination under sedation prior to surgery, to ensure suitability for surgery, with no other complicating factors.

In small-to-medium dogs, the cruciate-deficient joint is then usually well stabilized with an extracapsular repair (sometimes called a De Angelis procedure). In simple terms, the stifle is stabilised using a strong synthetic cord of material passed in a loop behind the fabella on the outside of the stifle and through a tunnel drilled in the front of the tibia. This is tensioned and crimped, and acts as an external replacement for the ruptured ligament.

Typically, six to eight weeks of exercise restriction is required post-operatively.

In larger dogs, the extracapsular procedure is not adequate to achieve good, long-term stability in the stifle. The advent of the triple tibial osteotomy (TTO) and some similar procedures has provided a biomechanical solution to the problem with excellent results.

In the TTO operation, the top of the tibia is reshaped by making a series of three cuts in the bone. The bone is then put back together with a metal plate and screws. The resulting change in architecture of the tibia does away with the need for a CCL-substitute, and following healing of the bone, there is no stifle instability. Eight to twelve weeks of exercise restriction and some rehabilitation work is required, but excellent results are achieved with proper care and attention.

If you notice any difference in the behaviour of your pet, please do not hesitate to contact us to book an appointment on (07) 3286 4020.

Sincerely,

Dr David Banks BVSc MVS

Raby Bay Veterinary Surgery Opening hours: 73 Shore Street West, Monday – Friday: 9am - 6:30pm Cleveland 4163 Saturday: 9am - 12pm (07) 3286 4020 Sunday: CLOSED

For more information, please visit www.rabybayvet.com.au