Understanding Shoulder Joint Anatomy

The shoulder is one of the most complex and mobile joints in the body. It allows you to lift, rotate and move your arm in multiple directions.

The shoulder is made up of three bones:

• Humerus – the upper arm bone
• Scapula – the shoulder blade
• Clavicle – the collarbone

The head of the humerus fits into the shoulder socket (glenoid) of the scapula, forming the main ball-and-socket joint of the shoulder. Surrounding the shoulder joint are the rotator cuff tendons, which help keep the shoulder stable and allow controlled movement by holding the head of the humerus securely within the shoulder socket.

These bones form two primary joints that can develop arthritis.

Glenohumeral Joint

The glenohumeral joint is the main shoulder joint where the head of the humerus fits into a shallow socket in the scapula called the glenoid. This ball-and-socket joint allows a wide range of motion.

Acromioclavicular (AC) Joint

The acromioclavicular joint is located where the collarbone meets the top of the shoulder blade (the acromion). Arthritis in this joint often causes pain at the top of the shoulder.

Healthy cartilage normally covers the surfaces of these joints, allowing smooth and painless movement. When this cartilage wears away, shoulder arthritis develops.

Types of Shoulder Arthritis

Arthritis of the shoulder can be classified into several forms, each with different causes.

Osteoarthritis (Wear-and-Tear Arthritis)

Osteoarthritis is the most common type of shoulder arthritis. It occurs when cartilage gradually wears down over time.

As the protective cartilage deteriorates:

• Bones begin to rub together
• Bone spurs may develop
• Joint inflammation increases

Osteoarthritis typically affects people over the age of 50 and is more common in the AC joint, though it can also affect the glenohumeral joint.

Rheumatoid Arthritis

Rheumatoid arthritis is an autoimmune disease that causes the body’s immune system to attack the lining of the joints (the synovium).

This inflammation can damage cartilage and bone over time and often affects both shoulders simultaneously. Rheumatoid arthritis commonly impacts multiple joints, including the hands, wrists, elbows, knees and shoulders.

Post-Traumatic Arthritis

Post-traumatic arthritis develops after an injury to the shoulder, such as:

• Shoulder dislocation
• Fractures of the humerus, scapula or clavicle
• Rotator cuff injuries

Damage from the initial injury can gradually lead to cartilage deterioration and joint degeneration over time.

Symptoms of Shoulder Arthritis

Common shoulder arthritis symptoms include shoulder pain that gradually worsens with activity.

Symptoms may include:

• Deep aching pain in the shoulder
• Pain that worsens with movement
• Stiffness or reduced range of motion
• Grinding, clicking or popping sounds (crepitus)
• Difficulty lifting the arm overhead
• Weakness in the shoulder
• Night pain that disrupts sleep
• Difficulty performing daily activities such as dressing or reaching overhead

Pain from shoulder arthritis may concentrate on the top or side of the shoulder and may extend down the arm. The degree of functional impact can range from mild discomfort to significant limitation.

Limited shoulder motion is a common feature of shoulder arthritis, particularly in advanced cases.

Pain location may vary depending on the joint involved:

• AC joint arthritis often causes pain at the top of the shoulder
• Glenohumeral arthritis may cause deeper pain in the back or center of the shoulder

Causes and Risk Factors

Several factors can increase the risk of developing shoulder arthritis.

Common causes and risk factors include:

• Aging and cartilage degeneration
• Previous shoulder injuries
• Repetitive overhead motion
• Rotator cuff tears
• Joint instability or dislocations
• Inflammatory conditions such as rheumatoid arthritis
• Genetic predisposition
• Heavy physical activity or occupational strain

Over time, these factors may lead to joint wear, inflammation and cartilage breakdown.

Diagnosing Shoulder Arthritis

To diagnose shoulder arthritis, your physician will perform a physical exam and review your symptoms and medical history.

During the evaluation, your physician may:

• Review your medical history
• Evaluate shoulder motion and strength
• Assess range of motion and muscle strength
• Identify areas of tenderness or swelling
• Listen for grinding or clicking during shoulder movement

Imaging tests are often used to confirm the diagnosis.

Common diagnostic tools include:

• X-rays to evaluate joint space narrowing and bone spurs. X-rays of an arthritic shoulder often show narrowing of the joint space and the formation of bone spurs (osteophytes).
• MRI scans to assess cartilage, ligaments and rotator cuff injuries
• CT scans for detailed evaluation of bone structures in complex cases

These tests help determine the type, location and severity of arthritis.

Non-Surgical Treatment for Shoulder Arthritis

Many patients with shoulder arthritis find relief through conservative, non-surgical treatments. Initial treatment typically focuses on maintaining mobility, reducing inflammation and relieving pain.

Common non-surgical treatments include:

Activity Modification

Avoiding activities that aggravate the shoulder can help reduce irritation and inflammation.

Anti-Inflammatory Medications

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, may help reduce pain and swelling.

Physical Therapy

Physical therapy helps improve:

• Shoulder flexibility
• Range of motion
• Muscle strength
• Joint stability

Strengthening the surrounding muscles can reduce stress on the joint.

Corticosteroid Injections

Steroid injections into the shoulder joint may provide temporary relief by reducing inflammation and pain.

Heat and Ice Therapy

Heat or ice applied for 20 to 30 minutes at a time may help reduce pain and stiffness.

Surgical Treatment Options

When non-surgical treatments no longer provide relief, shoulder arthritis surgery may be recommended.

The type of surgery depends on the severity of arthritis and the structures involved. Shoulder replacement is often recommended for advanced bone-on-bone shoulder arthritis.

Arthroscopic Shoulder Surgery

In early stages of arthritis, minimally invasive arthroscopic surgery may be used to:

• Remove inflamed tissue
• Smooth rough cartilage
• Remove bone spurs

This procedure may help improve joint movement and reduce pain.

Distal Clavicle Excision (AC Joint Surgery)

For arthritis affecting the AC joint, surgeons may remove a small portion of the collarbone to create space in the joint and reduce painful friction.

Shoulder Resurfacing

Shoulder resurfacing involves replacing only the damaged surface of the humeral head rather than replacing the entire joint. This procedure may be recommended for younger, active patients with localized arthritis.

Total Shoulder Replacement (Shoulder Arthroplasty)

In severe cases, total shoulder replacement surgery may be recommended.

During this procedure:

• The damaged humeral head is replaced with a metal ball
• The glenoid socket may be replaced with a plastic implant

This procedure can significantly reduce pain and restore joint function.

Reverse Shoulder Replacement

In patients with severe arthritis and rotator cuff damage, a reverse shoulder replacement may be recommended.

This procedure reverses the joint structure so the deltoid muscle powers shoulder movement instead of the damaged rotator cuff.

Complications and Related Conditions

Shoulder arthritis may lead to additional complications that affect joint function and surrounding tissues.

Bone spurs may develop along the edges of the shoulder joint as cartilage deteriorates. These growths can contribute to increased pain, stiffness and reduced mobility.

Rotator cuff tears may also occur as the tendons weaken or become damaged over time. In some cases, large rotator cuff tears combined with arthritis can lead to cuff tear arthropathy, a condition that causes severe pain and significant loss of shoulder function.

Another potential complication is avascular necrosis, which occurs when blood supply to the humeral head is disrupted. Without adequate blood flow, bone tissue may collapse, resulting in pain and joint damage.

Inflammatory arthritis conditions such as rheumatoid arthritis can also affect the shoulder and cause ongoing inflammation and joint deterioration.

Managing these complications often requires a combination of non-surgical treatments and, in more advanced cases, surgical procedures such as shoulder replacement.

Recovery and Rehabilitation

Recovery after shoulder arthritis treatment depends on the type of procedure performed.

Typical recovery may include:

• Wearing a sling during early healing
• Physical therapy to restore movement
• Gradual strengthening exercises
• Progressive return to daily activities

Full recovery may take several months, particularly after shoulder replacement surgery.

Following your surgeon’s rehabilitation plan is essential for the best outcome.

When to See a Shoulder Specialist

You should seek evaluation from a shoulder specialist if you experience:

• Persistent shoulder pain lasting several weeks
• Shoulder stiffness that limits daily activities
• Grinding or clicking sounds in the joint
• Difficulty lifting or reaching with the arm
• Pain that interferes with sleep

Early diagnosis can help prevent further joint damage and improve treatment outcomes.

Schedule an Appointment

If you are experiencing shoulder pain, stiffness or reduced mobility, the orthopedic shoulder specialists at OrthoTexas can help.

Our team provides comprehensive evaluation, advanced imaging and personalized treatment plans for shoulder arthritis and other shoulder conditions.