Canine Elbow Osteoarthritis

A common cause of front limb lameness in medium to large breed dogs of any age is the result of a condition traditionally called “elbow dysplasia”. Although some dogs have signs of lameness after adulthood, the problem arises during the development/growth from puppy to adult. Elbow dysplasia is traditionally described as one or more of three conditions seen in medium to giant breed dogs. These conditions are described as Ununited Anconeal Process (UAP), Fragmented Medial Coronoid Process (FCP), or Osteochondrosis (OCD) of the humeral condyle. The descriptive term used more recently to help describe “elbow dysplasia” is Medial Compartment Disease (MCD) of the elbow, because in >90% of cases only the medial compartment (the inner surface of the elbow is affected). The cause of this condition is multi-faceted with a variety of possible nutritional, hormonal, developmental, and environment factors contribute to this disease. There are two main abnormalities that can be seen in dogs with MCD; failure of endochondral ossification and incongruency. These abnormalities are most likely inter-related.

1. Failure of endochondral ossification- Endochondral ossification is the normal process during growth or healing of bone in which cartilage is turned into bone. In MCD on several areas of the elbow may have soft spots in the bone that can lead to separation of the cartilage flap and the underlying bone that can lead to inflammation and osteoarthritis in the joint.

2. Incongruity of the elbow (the bones don’t fit) indicates that during growth one of the three bones did not grow at the appropriate rate or length thus not allowing the bones to fit correctly in the joint. When this happens it leads to increased load (weight) on the medial (inner) compartment causing increased wear and pressure on the joint cartilage. In normal dogs both the lateral (outer) and medial (inner) compartments should be equally loaded during normal weight bearing 50/50. In dogs with MCD, they have increased weight distribution on the medial (inner) compartment.

Diagnosis of MCD is based on the patient’s history, age, breed, physical exam findings, and imaging of the elbow. If your dog is lame he/she should be evaluated by your primary veterinarian to help determine the cause and discuss potential treatment.

Treatment of MCD depends on several factors and the current condition of the cartilage in the elbow. At NEAMC, all cases get an inspection of the articular cartilage with an arthroscope which is needed to help guide treatment. The goal is to correct the abnormalities (Elbow incongruity or cartilage flap) to optimize the long term results. There have been several newer procedures that have shown some promise for this complex and difficult disease. Arthroscopic removal of loose fragments of cartilage has been a common treatment for this condition “pebble in the shoe” analogy. This works well in cases where there is no incongruity of the elbow but in many cases incongruity is a major factor. Using the analogy we can remove the pebble but what if the shoe doesn’t fit (Andy Torrington, DVM, DACVS).

A new procedure called the Proximal Abducting Ulnar osteotomy (PAUL) can be performed on adult dog’s to help transfer more weight from the medial compartment to the lateral compartment making the shoe fit.

Another treatment that has been used in human medicine and in canine elbows is the use of cartilage transplantation called Osteochondral Autograft Transfer (OATS). For severely damaged cartilage in the elbow can be repaired using transplanted cartilage from the knee. Both of these procedures are relatively new and long term data is lacking, but both are promising new treatments for a complex disease.

So if you feel that your pet is showing signs of lameness in the forelimb and has been on long term medication to help control their pain there are some other options to consider to help lessen the affects of osteoarthritis in the elbow and limit the need for long term medication.
Forrest Townsend, DVM, DACVS