Osteochondritis dissecans is a musculoskeletal disease that effects large breed dogs during early development. It occurs as a secondary ailment in dogs suffering from osteochondrosis, also called dyschondroplasia. In this condition, joint cartilage experiences abnormal placement during the calcification process. During development cartilage grows rapidly, and as it forms it becomes calcified to fuse with the edge of bones. In dogs with osteochondrosis, there is a defect in the process that leaves areas of cartilage uncalcified and unable to fuse normally with the bone.
The Cause of Osteochondritis Dissecans in Dogs
The uncalcified cartilage at the edge of bones is what leads to osteochondritis dissecans. The loose cartilage splits off from the bone, creating an abnormal projection. In some cases the loose cartilage can completely separate and break into fragments that sit in the joint space. These loose fragments are referred to as 'joint mice'. These fragments irritate the joint during movement, causing inflammation of the bone and cartilage.
The defect occurs most commonly in the shoulder joint, on the head of the humerus bone, and it can also occur in the elbow joints of the front legs. Many of the symptoms of elbow dysplasia are caused by cases of osteochondritis dissecans in the elbow joint. The stifle, or knee, is less commonly involved. Cases involving the stifle are often mistaken for luxating patella because both involve the femur and tibia bones. The first bone of the hock, or ankle, can be at risk but this is also an uncommon region for the defect.
Symptoms and Clinical Diagnosis of Osteochondritis Dissecans
The most visible symptom of osteochondritis dissecans is a gradual lameness that is displayed intermittently. It is most common in young, large breed dogs during rapid growth periods. The lameness may originate from problems that involve joints of the shoulder, elbow, stifle or hock. Limited or painful mobility may be most evident following exercise or physical stress. The dog may also show pain upon manual flexing and extension of the joint.
Diagnosis must be made with x-rays to determine if the dog is suffering from osteochondritis dissecans or a different musculoskeletal condition. Other conditions have similar symptoms, such as the disease panosteitis. If the dog is suffering from osteochondritis dissecans the x-rays will show fragmented or loose joint cartilage. Symptoms arise in dogs between 4 and 8 months of age, but many dogs cannot be officially diagnosed until approximately 18 months of age.
Symptomatic and Surgical Treatment of Osteochondritis Dissecans
Treatment of osteochondritis dissecans will require restriction of any activity or exercise that may put stress on the joints. A veterinarian will prescribe analgesics for relief of pain and discomfort. Chondroprotectants are often prescribed to improve joint lubrication and to slow the possible degeneration of the cartilage. A medication containing polysulfated glycosaminoglycan may be recommended for both pain relief and joint health.
Most dogs suffering from osteochondritis dissecans will require surgery to remove defective cartilage and 'joint mice'. Surgery has been most effective in cases involving the shoulder or elbow joints. Cases that involve the hock or the stifle can improve with surgery but are more likely develop degenerative joint disease later in the dog's life.