Understanding how your shoulder works
Your shoulder is a ball-and-socket joint. The ball portion of the joint consists of the rounded head of the upper arm bone (humerus), and the socket portion is made up of a depression (glenoid) in the shoulder blade. The humeral head (ball) fits into the glenoid (socket) creating the joint that allows you to move your shoulder. The joint is surrounded and lined by cartilage, muscles, and tendons that provide support and stability and make it easy for you to move.
It’s your shoulder joint that lets you rotate your arm in all directions. Your range of motion depends on the proper articulation of the humeral head upon the glenoid.
In a healthy shoulder joint, the surfaces of these bones where the ball and socket rub together are very smooth and covered with a tough protective tissue called cartilage. Arthritis causes damage to the bone surfaces and cartilage. These damaged surfaces eventually become painful as they rub together.
As you might expect, there are many different reasons why you could be feeling shoulder pain, including injury, infection, and arthritis.
A common cause of shoulder pain is osteoarthritis, a degenerative joint disease that causes the cartilage in your shoulder joints to break down. When that layer of cartilage—which is meant to cushion the joints and protect the surface of the bones—is damaged or worn away, your shoulder bones come in direct contact to each other, and that contact hurts. You can feel it when you’re lifting groceries, reaching for something, or simply raising your arms to brush your teeth or hair. It may even keep you up at night.
The factors leading to the development and progression of OA include aging, obesity, joint injuries, and a family history of arthritis (genetics). Although there is no cure, early diagnosis and treatment are crucial in slowing or preventing more damage to your joints.
In rheumatoid arthritis, the lining of the joint (synovium) becomes inflamed. The inflammation causes chemicals to be released that thicken the synovium and damage the cartilage and bone of the affected joint. This inflammation of the synovium causes pain and swelling.
The rotator cuff is the group of muscles and tendons that hold your shoulder together to give you strength and stability. Rotator-cuff arthropathy is a combination of two types of damage—not only has the cartilage deteriorated, but the rotator-cuff tendon that connects the muscle to the bone has also been severely worn or torn. This causes pain and may significantly limit your shoulder’s range of motion, making it nearly impossible to perform many tasks requiring shoulder movement.
The good news about arthritis in the shoulder is that it can be treated. Arthritis is a disease that typically worsens over the years, so it is common for treatment to involve more than one approach and to change over time. For some people, nonsurgical treatments such as lifestyle changes, medications, and physical therapy help alleviate the pain. For others, shoulder replacement surgery may be a long-term solution. Together, you and your doctor can determine the best treatment options for you.