Arthritis in the shoulder is defined by the inflammation and progressive degeneration of the joint surfaces. This process involves the breakdown of articular cartilage, the smooth, protective tissue that allows bones to glide past each other without friction. As this cartilage wears away, the bones of the shoulder joint begin to rub together, leading to pain and stiffness. The shoulder’s extensive range of motion makes it susceptible to wear and tear, complicating daily movements.
Key Locations of Shoulder Arthritis
The shoulder complex contains two primary joints where arthritis typically develops. The main ball-and-socket connection is the glenohumeral joint, where the head of the humerus, or upper arm bone, fits into the glenoid socket of the shoulder blade. Arthritis in this joint is a common site for severe degeneration, often causing a deep, internal ache.
A separate, smaller joint where arthritis often appears is the acromioclavicular (AC) joint, located at the very top of the shoulder. This joint connects the collarbone (clavicle) to the acromion, which is a part of the shoulder blade. Osteoarthritis is more frequently observed in the AC joint, causing pain that is focused on the top of the shoulder rather than deep within the joint.
Subjective Experience: Pain and Discomfort
The most consistent subjective indicator of shoulder arthritis is pain, which often worsens with activity and gradually intensifies over time. This pain is frequently described as a dull, constant ache deep within the joint, though sharp, stabbing pains can occur during certain movements. For many individuals, the discomfort is most noticeable at night, making it difficult to find a comfortable position and frequently disrupting sleep.
A very specific sensation associated with the condition is crepitus, which is the grinding, clicking, or crunching sound and feeling within the joint during movement. This noise occurs because the once-smooth cartilage surface has become rough and irregular, causing the bones to scrape against each other. The crepitus may range from a mild crackling sound to a loud, clunking sensation that is sometimes painful.
Visible Indicators and Physical Changes
Shoulder arthritis can manifest through several external signs that are observable upon inspection. In cases of inflammatory arthritis, such as rheumatoid arthritis, or during acute flare-ups, the joint may show signs of swelling. This swelling is sometimes accompanied by localized warmth or redness around the joint, which are classic signs of inflammation.
As the condition progresses, the body may attempt to stabilize the damaged joint by growing small, excessive projections of bone called osteophytes, or bone spurs. These bony outgrowths can be felt as a hard, irregular enlargement around the joint line, particularly in the AC joint. A visible sign is muscle atrophy, or wasting, in the surrounding shoulder muscles. This atrophy is a consequence of decreased use, as the individual avoids painful movements, leading to measurable weakness.
Impact on Movement and Daily Activity
The physical changes within the arthritic joint directly result in a noticeable restriction in the shoulder’s range of motion. This loss of mobility is progressive, manifesting as an inability to fully lift the arm away from the side or overhead. Patients often exhibit difficulty with internal rotation, which is the movement required to reach behind the back, such as when tucking in a shirt or fastening a bra.
These limitations transform routine tasks into challenging or painful obstacles. Simple actions like putting on a jacket, reaching a high shelf, or brushing one’s hair become frustratingly difficult. The inability to comfortably position the arm and shoulder also impacts activities requiring sustained arm use, such as driving or working at a desk. The cumulative effect of restricted movement and persistent pain diminishes the quality of life.