Glenohumeral Osteoarthritis

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Glenohumeral Osteoarthritis

Glenohumeral joint osteoarthritis is a degenerative joint disease characterized by pain, stiffness, and decreased shoulder function. Although osteoarthritis commonly affects joints like the knee, interphalangeal joints, and spine, it is relatively uncommon in the glenohumeral joint. When it does occur in the shoulder, it is more frequently seen in individuals over the age of 65.

Several key structures stabilize the glenohumeral joint. The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) play a dual role by facilitating movement and providing dynamic stability. Additionally, the joint capsule and ligaments, including the superior, middle, and inferior glenohumeral ligaments, offer crucial static stability. The articular surfaces of the joint are covered with hyaline cartilage, which ensures smooth and pain-free movement. In osteoarthritis, this cartilage progressively deteriorates, resulting in increased friction between the articulating bones, leading to pain, stiffness, and reduced joint function.

As osteoarthritis progresses, synovial inflammation becomes a key feature. The synovium, which lines the joint capsule and produces synovial fluid to lubricate the joint, becomes chronically inflamed (synovitis). This inflammation contributes to pain and swelling, exacerbating joint stiffness and further reducing the range of motion. Over time, the joint capsule may thicken due to persistent inflammation, leading to more pronounced movement restrictions. These pathological changes are often accompanied by the formation of osteophytes (bone spurs) around the joint margins, which can cause mechanical obstruction and increase pain.

Clinically, patients with glenohumeral osteoarthritis typically present with a characteristic set of symptoms, including chronic shoulder pain that worsens with activity, significant joint stiffness—especially after periods of inactivity—and crepitus (a grating or grinding sensation during joint movement). Pain is often more pronounced in the morning and may improve with mild activity as the joint “warms up.” On physical examination, tenderness over the joint, muscle atrophy, and a reduction in both active and passive range of motion are commonly observed.

Given that glenohumeral osteoarthritis shares several symptoms with adhesive capsulitis, such as pain and restricted motion, plain radiography is essential to confirm the diagnosis and distinguish between these conditions.

Osteoarthritis often follows a diurnal pattern of symptom severity, similar to rheumatoid arthritis, with fluctuations in pain and stiffness throughout the day influenced by activity and rest. In osteoarthritis, patients commonly experience joint stiffness upon waking, which typically resolves within 30 minutes, a key feature differentiating it from the prolonged morning stiffness associated with rheumatoid arthritis. As the day progresses, symptoms of osteoarthritis may worsen with increased physical activity, leading to more significant discomfort and stiffness later in the day.

Glenohumeral osteoarthritis can develop due to a combination of factors, including:

• Age-related cartilage wear
• Previous injuries
• Repetitive use
• Genetic predisposition
• Inflammatory diseases
• Congenital abnormalities
• Metabolic disorders

Shoulder Pain Differential Diagnosis

• Glenohumeral Joint Dysfunction
• Glenohumeral Osteoarthritis
• Bicipital Tendinopathy
• Subacromial Impingement Syndrome
• Rotator Cuff Tendinopathy
• Rotator Cuff Tear
• Myofascial Pain Syndrome (e.g., pectoralis major, pectoralis minor, supraspinatus, infraspinatus muscles)
• Coracobrachialis Dysfunction
• Biceps Brachii Dysfunction
• Subacromial Bursitis
• Acromioclavicular Joint Pathology
• Adhesive Capsulitis (Frozen Shoulder)

Classification

• Primary (idiopathic) osteoarthritis – Occurs without an identifiable underlying etiology, such as trauma or congenital anomalies. It is typically attributed to age-related degeneration and general wear and tear of the joint.
• Secondary osteoarthritis – Develops as a result of identifiable predisposing factors, including congenital anomalies, inflammatory arthropathies, previous trauma, or repetitive joint loading due to occupational, athletic, or habitual activities. These factors accelerate joint degeneration, leading to osteoarthritis.

Grading

Grading osteoarthritis in the glenohumeral joint can be achieved using a modified version of the Kellgren-Lawrence (K-L) grading system, along with clinical evaluation and imaging techniques. Below is an outline of the grading system specifically adapted for glenohumeral osteoarthritis:

Modified Kellgren-Lawrence Grading System for Glenohumeral Osteoarthritis (OA)

Grade 0: No Radiographic Features of OA

• Description: No signs of osteoarthritis.
• Radiographic Findings: Normal joint space, no osteophytes, normal bone structure.

Grade 1: Doubtful OA

• Description: Early or minimal signs suggestive of osteoarthritis.
• Radiographic Findings: Possible tiny osteophytes, no significant joint space narrowing.

Grade 2: Mild OA

• Description: Definite signs of osteoarthritis with mild symptoms.
• Radiographic Findings: Definite osteophytes, possible slight narrowing of the joint space, mild subchondral sclerosis.

Grade 3: Moderate OA

• Description: Moderate signs of osteoarthritis with more pronounced symptoms.
• Radiographic Findings: Moderate osteophytes, definite joint space narrowing, moderate subchondral sclerosis, and possible cyst formation.

Grade 4: Severe OA

• Description: Severe signs of osteoarthritis with significant symptoms and joint dysfunction.
• Radiographic Findings: Large osteophytes, marked joint space narrowing, severe subchondral sclerosis, cyst formation, and deformity of the joint surfaces.

Kellgren-Lawrence (K-L) Grading System: Arden N, Nevitt MC. Osteoarthritis: Epidemiology. Best Practice & Research Clinical Rheumatology. Vol. 20, No. 1, pp. 3–25, 2006.

• Gradual onset of deep, aching shoulder pain and stiffness, typically developing over months to years.
• Pain is worse in the morning but improves with mild activity.
• Pain is aggravated by excessive or repetitive activity.
• Pain is reduced with rest.
• Patients may report a history of prior shoulder trauma.
• Reduced shoulder mobility, often accompanied by functional limitations.
• Crepitus (a grating or grinding sensation) may be reported during joint movement.
• Pain intensity may fluctuate with changes in barometric pressure.

• Tenderness along the anterior joint line.
• Localized anterior swelling.
• Decreased range of motion, particularly in external rotation and abduction.
• Impaired glenohumeral motion, as demonstrated by positive Apley Scratch tests and abnormal scapulohumeral rhythm.
• Atrophy of the rotator cuff muscles, particularly noticeable over the scapula.
• Presence of crepitus (grating or cracking sensation) during joint movement.

• Plain radiography is typically performed to assess the presence and severity of osteophyte formation, joint space narrowing, and subchondral sclerosis, providing a clear picture of the degenerative changes in the glenohumeral joint.
• MRI may be utilized to evaluate soft tissue structures, including the rotator cuff and labrum, allowing for the detection of rotator cuff tears, tendinopathy, or labral irregularities that may accompany or exacerbate the condition.

The following are examples of red flags for shoulder pain:

• A history of significant injury
• Severe pain
• Unrelenting pain
• Nocturnal pain
• Unexplained weight loss
• Fever
• Deformity
• Significant swelling
• Presence of tingling, numbness, burning, or other neurological impairment
• Significant loss of range of motion
• Severe tenderness on palpation or severe pain with any examination procedure

If any red flags are identified during history taking and clinical examination, referral for urgent medical evaluation and further investigation is warranted.

Sleeping Posture Advice

Patients with glenohumeral osteoarthritis may experience shoulder discomfort during sleep. Sleeping with the involved arm supported by a pillow may reduce that discomfort. An example for right shoulder pain is parented below.

Rheumatoid Arthritis vs. Osteoarthritis: Key Differences

Rheumatoid Arthritis

• Typically involves both shoulders (bilateral), reflecting its systemic nature.
• Persistent shoulder pain is often accompanied by swelling and warmth over the affected joints.
• Morning stiffness lasts more than 30 minutes.
• Fatigue, malaise, and low-grade fever are commonly present.
• Frequently starts in smaller joints (e.g., fingers) before progressing to larger joints like the shoulders.

Osteoarthritis

• Commonly begins unilaterally, particularly in the dominant arm.
• Deep, aching pain that worsens with activity and improves with rest.
• Morning stiffness typically resolves within 30 minutes.
• Crepitus is common during joint movement.
• Gradual reduction of shoulder range of motion over time.