Cruciate Ligament Rupture

Hind limb lameness is often caused by rupture of the cranial cruciate ligament in the stifle or knee joint. This condition can be either;

  • Degenerative (progressively getting worse) and occurring over an extended period of time.
  • Acute (sudden onset), due to rotational instability at a specific time e.g. injuring it while chasing a ball.
  • Acute on chronic An sudden force causes the degenerated fibers of the ligament to tear.

The knee joint consists of the top of the tibia/fibula associated with a padded meniscus cup in contact with the lower surface of the femur.

Between the two bones are the cruciate ligaments – cranial and caudal, that cross over in the joint and act to keep the bones from sliding over each other. Collateral ligaments run on either side of the joint to prevent the bones from sliding side to side.

This injury can occur at any age and in any breed, but most frequently occurs in middle-aged, overweight medium to large breed dogs.

 

How does the injury occur?

The ligament injury occurs when the forces involved are too strong in a certain direction. Usually an acute (sudden) cruciate injury occurs when the lower half of the leg remains still and the upper half above the knee joint is forced to rotate.

Such events can occur when an animal leaps up or down and twists with the take-off or landing, places their foot in a hole or between stairs and continues to move forward, or even suddenly stops running or changes direction. The cranial cruciate ligament is the one most commonly affected in these situations.

How do you diagnose cruciate ligament rupture?

Diagnosis is based on history and physical exam. Dogs with a ruptured cruciate ligament tend to be quite lame. Clinically, joint effusion may be palpable on the affected limb. Patients with a cruciate ligament deficient knee tend to manifest pain on extension of the joint.

Diagnosis involve manipulation of the joint under heavy sedation and radiographic assessment of the affected leg. Common tests performed are:

The “cranial drawer sign” test

This involves holding the stifle joint with one hand on the femur and one on the tibia/fibula. The vet then tries to move the bones forward and backward to produce “draw” or give. In a normal knee joint there is little to no movement and there is no pain. In an animal with a rupture there is marked movement or sliding of one bone in front of the other, as shown in the diagram below. Pain can accompany the movement.

The Tibial Thrust test

This involves the stifle held in slight flexion and the hock being flexed and extended to elicit thrust from the tibia forward in relation to the femur.

Occasionally a general anaesthetic may be required if palpation is too painful for the animal or if the animal is not relaxed enough to allow a thorough examination.

 

 

Tibial Thrust Test (left outside view)

Ligament strains do occur but generally we see a partial or complete rupture to the ligament. The only way to stabilise the stifle is through surgery. Without surgery, the ligament will not repair or restore its important function. This is the most common cause of hind limb lameness in dogs. For this reason, several types of surgery have been done throughout the years, but patient selection is very important to obtain the best outcome.

A better prognosis is given for animals that are;

  • Not overweight. If your pet is overweight, we recommend feeding them a calorie controlled diet until they reach their goal weight. We can tailor a weight loss program for your pet.
  • Can be kept restrained over the recovery period.
  • Are less boisterous.

 

What does the surgery do?

Surgically, the stifle joint is opened up and explored to confirm the diagnosis of a partial or complete cruciate ligament rupture. Remaining strands of ligament can at this time be cleaned out, the joint flushed and the meniscus inspected and treated for tears. The surgeon can then begin the repair.

The three most common techniques to repair a ruptured cruciate are;

  1. TPLO (Tibial Plateau Levelling Osteotomy)
  2. TTO (Triple Tibial Osteotomy)
  3. TTA (Tibial Tuberosity Advancement)
  4. De Angelis Technique