Shoulder arthritis can be painful and make activities such as throwing a ball, lifting a heavy dish from a high cupboard, or even steering a car difficult. The shoulder is engaged in almost all arm movements, so painful movement of the shoulder joint affects many everyday activities.
Typically, shoulder arthritis is indicated by a gradual onset of pain, tenderness and limited range of motion. Shoulder arthritis comes in many forms, most commonly osteoarthritis, followed by forms of inflammatory arthritis, such as rheumatoid arthritis or gout.
Shoulder osteoarthritis is a degenerative joint disease that involves two primary processes:
- The cartilage in the joints breaks down
- Abnormal bony growths, called osteophytes or bone spurs, develop in the joint
While factors such as genetics also play a part, shoulder cartilage degeneration is often preceded by an injury - sometimes years earlier - or by chronic mini-traumas from overuse. The degeneration eventually leads to abnormal joint function, pain and inflexibility.
The osteoarthritic process is gradual, with symptoms that may come and go and eventually worsen over time. The primary symptom of shoulder osteoarthritis is pain in one or both shoulders, for example:
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- Shoulder tenderness and pain that comes and goes, possibly with a chronic low level of pain punctuated by intermittent flare-ups of more intense pain
- Pain with certain activities, such as golfing, throwing a ball, lifting items overhead, putting on a seat belt, or brushing teeth.
Even moderate shoulder osteoarthritis can be extremely painful and debilitating, interrupting sleep and affecting everyday habits.
While there are many similarities in the symptoms and treatments from various types of shoulder pain, this article focuses on osteoarthritis of the shoulder’s major joint, the ball-and-socket joint called the glenohumeral joint. In this article the terms “shoulder” and “glenohumeral joint” will be used interchangeably.
An in-depth review of shoulder arthritis symptoms, causes and risk factors, diagnostic process, non-surgical and surgical treatments for osteoarthritis of the shoulder are included in this article.
Shoulder Joint Anatomy and Osteoarthritis
The shoulder is a complex piece of anatomy that includes four joints where the humerus (upper arm), scapula (shoulder blade), and clavicle (collarbone) meet. The shoulder has four joints, and the major joint is called the glenohumeral joint.
- The glenohumeral joint is where the head of the humerus nestles into a shallow socket of the scapula called the glenoid. This ball-and-socket construction allows for circular movement of the arm, and is credited for the shoulder’s wide range of motion.
- The acromioclavicular joint is located where the clavicle glides along the acromion, which is at the highest point of the scapula. While it is not discussed in this article, the acromioclavicular joint is more susceptible to osteoarthritis than the glenohumeral joint.
- Explore the symptoms and treatments for Acromioclavicular (AC Joint) Osteoarthritis
Strong, slippery articular cartilage lines the surface of the humeral head and glenoid at the areas where they meet. The cartilage helps the bones glide against each other and acts as a buffer to protect the bones from impacting one another. The articular cartilage is naturally thinner in the shoulder joint than in weight-bearing joints such as the knees and hips.
- Read more about Shoulder Anatomy
How Shoulder Arthritis Causes Pain
An arthritic shoulder has thinned, damaged or missing articular cartilage. The damaged cartilage is not in and of itself a source of pain or other symptoms. Instead, the damaged or missing cartilage allows friction between bones, which in turn causes shoulder pain and related symptoms.
In an arthritic shoulder, the articular cartilage is thinned, damaged or entirely worn away. When the cartilage has deteriorated in such a manner, the following process ensues:
- New cartilage may be produced, but the new cartilage cells will grow in irregular, bumpy patterns rather than the original smooth form. In the glenohumeral joint, the result is that the head of the humerus and the glenoid rub and grind against one another.
- To compensate for the deteriorated or missing cartilage, the bones in the joint may produce small scalloped growths called osteophytes, or bone spurs. Compensatory bone changes may even cause the humeral head’s rounded surface to flatten and/or large osteophytes to grow on the humeral head in the form of a “goat’s beard.” In turn, there is even more friction in the glenohumeral joint.
It is important to note that cartilage does not contain nerves, so damaged cartilage is not the primary source of pain in shoulder osteoarthritis. Likewise, bone spurs are a normal sign of aging and the presence of bone spurs alone are not a cause for concern. However, the friction between bones and other resulting abnormalities in the shoulder can cause discomfort and pain. For example, as cartilage in the glenohumeral joint deteriorates the joint space shrinks and can lead to tendinitis.
Osteoarthritis of the shoulder is less common than osteoarthritis of weight-bearing joints such as knees and hips. For those who do have it, however, shoulder arthritis can be severely painful and debilitating.
It is generally advisable to seek medical attention for any type of chronic discomfort or minor pain in the shoulder. Understanding the symptoms and causes of shoulder osteoarthritis, getting an accurate diagnosis and following an appropriate treatment program can encourage healthy joint function and minimize or halt the progression of symptoms. As a general rule, if shoulder arthritis is diagnosed and treated early in the disease process, the outcome will be better for the patient in terms of less pain and fewer complications.