The cruciate ligament connects the femur to the tibia and stabilizes the joint. Damage to a ligament is called a sprain, of which there are 4 types, ranging from a minimal tear, right through to a full tear of the ligament, and damage to the bone.
The cruciate ligament of the dog deteriorates over time and can be likened to the fraying of a rope. Other than general wear and tear, damage can also occur as the result of trauma, such as a sharp turn to catch a frisbee or ball, or stepping awkwardly into a hole. Even living on a slippery surface such as laminate flooring can cause damage to the cruciate ligament. Some breeds are predisposed to cruciate ligament damage, these include Boxers, Collies, Rotweillers, West Highland Terriers, and giant breeds. Both obesity and hormonal factors can both contribute towards cruciate ligament damage.
The dog may present with lameness, they may limp, be unable to bear weight equally, or maybe even not at all. They may cry out in pain and there may be inflammation, swelling and heat radiating from around the joint capsule. The stifle may appear abducted and the toes may be just touching the floor in semi flexion.