Joints allow movement between bones. Movement is controlled by ligaments and tendons which are made of very tough tissue which are attached to the bones. The knee joint is particularly susceptible to damage from strained or torn ligaments.

The medical term for a dislocation of the kneecap. It is most often seen in the smaller breeds and may be inherited. Many Poodles, Chihuahuas, and other small breeds inherit a very shallow groove on the femur in which the kneecap must ride. Any injury resulting in a stretching or twisting of the knee causes the ligaments to tear allowing instability of the patella in its rightful place. It usually is displaced to the inside of the leg and often may pop back into proper location when the leg is straightened taking pressure off the joint. The leg usually appears to be turned inward when viewed from the rear of the dog. Many times, both rear legs are affected. It is often possible to push the affected patella in and out of proper position. Surgery is often necessary if lameness persists to prevent later arthritis. Surgery involves deepening the notch in the femur where it should remain positioned and tightening of the various ligaments.

The Anterior Cruciate Ligament attaches the femur to the tibia (shinbone) preventing excessive motion between these two bones keeping the joint stable. Over-extension of the knee joint may tear this ligament allowing the two bones to slide back and forth causing pain, lameness, and instability.

Excessive movement over a period of time leads to arthritis and pain. Overweight dogs are most susceptible due to the excess pressure created on the joints. Conservative medical therapy initially using anti-inflammatory drugs may allow healing if the ligaments are merely stretched instead of being torn. Complete rest is essential for any chance of healing to occur. If the ligamentis actually torn, even partially torn, surgical repair will be needed to form new ligaments and tighten the joint giving stability needed for normal movement and activity.

COLLATERAL LIGAMENT RUPTURE of the knee allows the femur and tibia to move from side to side. Surgical repair involves reconstructing these ligaments.