Cruciate Disease in Dogs

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Cruciate disease is the most commonly operated orthopaedic disease in dogs. It happens in all sizes of dogs but more frequently in larger breeds. Once one leg is affected there is a 50% chance the other leg will rupture the ligament due to the over compensation of weight bearing in the healthy leg.

How The Cruciate Ligament Works

• The femur (large bone of the thigh) and the tibia and fibula (2 smaller bones in the shin) meet to form the knee joint.
• Cartilage covers the ends of bones protecting them and the ligaments, tendons and muscles hold the bones in place, stabilising the joint and enabling movement.
• There are two major ligaments; the caudal and cranial cruciate ligaments that support the knee joint.
• The meniscus (a cushion between the bones) absorbs impact and provides a gliding surface between the femur and tibia.
• When a step is taken, the cruciate ligaments tighten and keep the bones from moving apart.
• One problem with the knee joint is that the floor of the tibia is sloped backwards and when a lot of force is placed on the knee the femur slides backwards. This can cause the ligament to rupture and the meniscus to tear.

Causes

• Acute rupture; caused by sudden, severe twisting of the ligament.
• Chronic rupture; occurs in older animals when the ligaments have degenerated with age, they weaken and partially tear, the joint becomes unstable and degenerative joint disease develops.

Treatment: Medical Treatment

• Best in dogs weighing less than 10kg and generally unsuccessful in larger dogs.
• Lameness normally resolves within 6 weeks with rest and anti-inflammatory drugs.
• Instability does persist and secondary degenerative joint disease (arthritis) frequently develops.

Treatment: Surgical Treatment

Performed to stabilize the joint and recommended in patients of any size to ensure restoration of optimum function.

Two major types;

1. Extracapsular technique; A suture is placed outside the knee joint which acts as a cruciate ligament. This procedure is less invasive than others and the complications less severe.
2. Extra-articular technique (or TPLO) ; Normally a ‘specialist’ procedure. The tibial slope is ‘flattened’ by cutting a portion of the tibia and reattaching it using plates and screws. By changing the conformation of the tibia, the joint is stabilized.
   • After surgery, the dog must be rested for 2 weeks. Most dogs start bearing minimal weight on the leg by this time. The dog generally has to be rested with gradual increases in lead walking for a minimum of 4-6 weeks.
   • Complications; occur in cruciate surgery in approximately 5-10% patients.

Minor problems include; bleeding, bruising, reaction to suture material, irritation associated with implants, fluid formation and superficial infections of the incision. More severe problems include; implant failure and deep infections of the joint.