The knee (or stifle) consists of the femur above and the tibia below. Dogs have knee cap (patella) at the front like us and then two small bones at the back called fabellae. There are two crescent shaped cartilages which lie on top of the tibia which help to cushion the joint. Inside the joint there are two ligaments which anchour the tibia to the femur. These cross over through the middle of the joint. These are called the cranial cruciate ligament and caudal cruciate ligament.
It is the cranial cruciate ligament that is damaged in canine cruciate disease.
Diagnosing Cruciate Rupture
When a dog ruptures a cruciate ligament owners will commonly report an acute injury. The dog may be playing and then suddenly pull up lame and not touch the foot down. It may improve somewhat over a week but the lameness usually persists and does not resolve and eventually that's where the vet comes in
The vet will look for some telltale signs that there is a ruptured cruciate.
1. The drawer sign - this is where there is excessive forwards movement by the tibia in relation to the femur (like a drawer opening).
2. Effusion - swelling can occur around the stifle.
3. Medial buttress - there can be a swelling on the inside of the tibia
4. Xray - Sometimes the usual signs of cruciate disease aren't so obvious. An xray can be another aid to rule in or rule out disease.
The key to the diagnosis of the ruptured cruciate ligament is the demonstration of an abnormal knee motion called a drawer sign. It is not possible for a normal knee to show this sign.
The Drawer Sign
The drawer sign is exhibited when the tibia is able to forward from underneath the femur (similar to a drawer opening). If this action is demonstrated, the cruciate rupture is confirmed. The motion is exaggerated here for the purposes of illustration. Illustration by MarVistaVet.
The veterinarian stabilizes the position of the femur with one hand and manipulates the tibia with the other hand. If the tibia moves forward (like a drawer being opened), the cruciate ligament is ruptured. (See a video of this manipulation.)
Another method is the tibial compression test where the veterinarian stabilizes the femur with one hand and flexes the ankle with the other hand. If the ligament is ruptured, again the tibia moves abnormally forward.
If the rupture occurred some time ago, there will be swelling on side of the knee joint that faces the other leg. This is called a medial buttress and is a sign that arthritis is well along.
Risk factors for Rupture
There is a small percentage of dogs that are young and healthy with great anatomy that are unlucky enough to have a bad fall and rupture the ligament.
In the vast majority of dogs that damage their cruciate it is not large trauma that causes the issue. Most dogs will have some risk factors that will likely have stressed the ligaments causing a chronic weakening of the structure. This weakened ligament is then less robust and the the force that is required to cause a cruciate tear may not be substantial.
The risk factors that may make your dog more prone to cruciate rupture include
- Breed - There are certain breeds whose stifle biomechanics makes them more prone. These include Staffordshire Terrier, Rottweiler, Labrador and Golden Retriever.
- Obesity - Excess weight means more strain is placed on the cruciate.
- Early desexing - This can change the biomechanics of the stifle and increase the risk.
The current gold standard for Cruciate disease in canines is Tibial Plateau Leveling Osteotomy (TPLO) with follow up rehabilitation. This is not to say that other that surgical techniques and other management tools may be helpful but TPLO and rehab have the best evidence for benefit to date.
Avoidance of surgery and conservative management utilising rehabilitation and medications/ supplements is sought by some owners. There may be many reasons for this. Conservative management is possible with some dogs resulting in a good return to function but is not suitable for every patient.
Likely Course of disease
A dog that has ruptured it's cruciate will develop arthritis in the stifle regardless of whether it has TPLO surgery or not. An untreated joint will end up with quite severe arthritis. If the TPLO procedure is performed by an experienced surgeon the arthritis is generally less than a conservatively managed stifle.
It is important that every dog that has cruciate disease has lifelong joint support supplements.
Dogs that have ruptured a cruciate often have a partial rupture in the other stifle. This should be checked by your vet. If there is not concurrent disease the risk of rupturing the cruciate in the other leg in the next few years is moderate to high.
A large factor in the recovery of a dog from cruciate disease is whether or not the meniscus remains intact. A small tear in this small structure can elicit a lot of pain and prevent some dogs from weight bearing. Meniscal tear can happen soon after the initial injury or following surgery. The suspicion for meniscal tear is raised for a dog that is taking an extended time to weight bear or if there is a setback after initial improvement following surgery.
The exercises and treatment given in rehabilitation will depend on if your dog is conservatively managed or post surgical. It would also depend on what stage your dog is in recovery. Initial confinement, home exercise program, underwater treadmill and laser therapy can all be helpful in your pet's recovery.
Conservative treatments offered by Balance Vet Rehab that may be beneficial for these pets include:
Our clinic utilises an experienced specialist surgeon who services our clinic for cruciate surgeries to ensure an optimum outcome for your pet.
Laser therapy can help dogs with the inflammation that can occur straight after injury or immediately after surgery. It can also help in pets with ongoing chronic degenerative changes associated with cruciate rupture.
Preoperative low level laser therapy in dogs undergoing tibial plateau levelling osteotomy: A blinded, prospective, randomized clinical trial Cleo P. Rogatko et al
The appropriate home exercise program is vital to ensure optimum recovery after cruciate surgery. It can help reduce pain and build strength in the affected leg.
Evaluation of the clinical effects of diet and physical rehabilitation in dogs following tibial plateau leveling osteotomy Wendy I. Baltzer et al
Effects of postoperative rehabilitation on limb function after cranial cruciate ligament repair in dogs. Marsolais GS et al
The underwater treadmill is a great tool to have to encourage weight bearing and eventually recovery of muscle in dogs with cruciate rupture.