Hip and Elbow Dysplasia

• Dysplasia is a term that technically means poor or abnormal formation. “Joint dysplasia could be considered to be the result of an imbalance between weight bearing forces and the maturation of cartilage to bone. If cartilage can convert to bone to form normal shaped articular (joint) surfaces prior to abnormal stresses being placed on the joint, dysplasia can be avoided. However, if the cartilage model becomes malformed prior to the final conversion to bone, the joint will be dysplastic. The severity of each form of dysplasia varies, creating disease with differing clinical significance.” (JP Morgan et al 1999).
• Osteochondritis (OC) arises from an error in conversion of cartilage to bone in the rapidly growing dog, resulting in the development of thickened and/or necrotic cartilage within joints and growth plates.
• Osteochondritis Dessicans (OCD) is a progression of OC resulting in deep cracks and fissures within the cartilage, as well as joint swelling and lameness. OCD results from a combination of genetic, nutritional and rapid growth factors.
• Osteoarthritis (OA) develops over time if there are remnants of cartilage flaps retained within joints and where incongruent joint surfaces have developed subsequent to the OCD lesions.
• Osteochondritis is a developmental bone disease characterised by defective cartilage in various to multiple joints. The main feature of OC is a failure of the cartilage to properly convert to bone during the growth process. Due to rapid growth, the cartilage cells divide at a normal or increased rate, but the cells do not fully mature. This can result in thickening of the cartilage in various areas of the joint and a delay in bone formation.

Hip Dysplasia (HD)

This is a condition that is very common throughout the whole range of dog breeds from the very small to the giant breeds. It is more commonly seen in the heavier bone to muscle ratio breeds where the overall ligamentation is loose. Hip dysplasia, is by definition, an ill fitting hip. The hip is a ball and socket joint, where the deeper the socket (ideally sufficiently deep to hold 2/3rds of the head of the femur), the better fit of the femoral head to the socket, combined with tight ligaments, the better the hip.

The various components that combine to give an unstable hip are combinations of the following:-

• shallow hip socket (the acetabulum)
• an ill fitting head of the femur (head too small, neck too short and steep)
• excessive looseness of ligamentation

A combination of the above factors leads to instability of the joint.

The joint capsule is attached around the outer edges of the joint and to the periosteum. When the edges of the joint capsule are constantly being pulled, the periosteum is lifted and new bone is laid down in an attempt to stabilise the joint.