What Is Osteoarthritis?
Osteoarthritis (OA) is the leading cause of disability in the USA. It is estimated that 1 out of 3 adults will suffer from arthritis. By definition osteoarthritis or degenerative joint disease (DJD) is a progressive disorder involving inflammation and degradation of the articular or hyaline cartilage on the ends of bones in various joints of the body. This type of cartilage has no nerve supply and is very resistant to friction making it perfect for weight bearing surfaces. When OA begins, the affected cartilage usually develops small tears in the joint surfaces that begin to progress into larger more substantial areas of wear. In normal joints, articular cartilage is capable of repairing minor wear in a limited capacity through chondrocyte production (cells that form new cartilage). When the damage rate becomes too significant and continuous, these cells can no longer repair the affected area. When this happens the process of degenerative joint disease begins. As this disease progresses, eventually the cartilage will wear out to a point where the underlying bone becomes exposed. This subchondral bone is rich in nerve supply and unlike hyaline cartilage is very prone to further wear from friction When this happens in a joint, the bones connecting the joint rub together resulting in pain and joint inflammation. This is where the term “bone on bone” comes from. As OA progresses, the affected joint will begin to form bone spurs around the joint margins and eventually lead to a noticable angular deformity at the joint. Although it is primarily found in weight bearing joints (knees and hips), it also occurs in non-weight bearing joints such as the shoulder.
DJD symptoms usually begin as stiffness (especially in the AM), pain with prolonged weight-bearing or immediately following activity, swelling, crepitus (audible grinding or ratcheting) and loss of motion. Symptoms vary from person to person and joint to joint.
The shoulder joint is also a ball and socket joint. Opposite to that of the hip, it is the most mobile joint in the body. OA is less common due to the fact that the shoulder is a non-weightbearing joint. The two affected joint surfaces are the humeral head and the shoulder socket known as the glenoid fossa. Many times, progressive rotator cuff disease and ultimate cuff failure (rotator cuff arthropathy) begin the degeneration of the articular cartilage in the shoulder. Symptoms of OA in the shoulder are commonly lateral arm pain with the inability to move the arm through its full range of motion. In the later stages, “catching”, “ratcheting” and “popping” as very common with progressive loss of are motion and significant pain to follow.