Current Understanding of Medial Compartment Disease of the Canine Elbow

Introduction
Medial compartment disease is a complex and challenging condition which remains incompletely understood despite extensive bench top and clinical research over the past few decades. The condition was originally described as fragmented coronoid process (FCP), and it was proposed that surgical retrieval of osteochondral fragments would carry a good prognosis. However, longer term clinical studies have shown that outcomes were often suboptimal and osteoarthritis frequently appeared to progress irrespective of treatment. FCP was initially thought to be a form of osteochondrosis, but this has not been supported by histological studies. The improved visualization of the joint with arthroscopy has allowed the condition to be better defined, and it is now clear that a spectrum of changes can be seen affecting the entire medial compartment of the elbow rather than just the medial coronoid process (MCP). This has led to the condition being redefined as ‘medial coronoid process disease’ or ‘medial compartment disease’ (MCD).

Arthroscopic observations
The changes affecting the elbow include various patterns of fissuring and fragmentation of the MCP, cartilage lesions of variable severity affecting the medial aspect of the humeral condyle and the distal extent of the trochlear notch, and occasionally linear erosion of subchondral bone. True osteochrondrosis of the medial humeral condyle can occasionally be seen, either alone or more frequently in combination with other lesions affecting the medial aspect of the elbow joint, but this is much less common. Osteochondrosis appears to be histologically and genetically distinct from MCD and can be classified as a separate condition.  [...]