Glenohumeral osteoarthritis is a degenerative joint disease characterized by wear of the articular cartilage on the humeral head and glenoid. For patients affected, it results in significant pain, loss of range of motion, and difficulties performing activities of daily living. In addition to these physical limitations, the presence of osteoarthritis can greatly affect emotional and psychological well-being, as it can lead to significant depression and anxiety.¹ Although less prevalent than osteoarthritis of the hip and the knee, osteoarthritis of the shoulder still is an extremely common musculoskeletal condition, affecting up to 17 percent of patients presenting with shoulder pain.^1,2 Notably, in 2017, there were 104,575 shoulder replacements, which is the end-stage treatment of shoulder arthritis performed in the United States.³ The risk of developing glenohumeral osteoarthritis greatly increases with age, with the greatest risk in individuals over sixty years old.^4,5 In this age group it is estimated that over one-third of individuals are affected by glenohumeral osteoarthritis.⁴ Other risk factors associated with the development of glenohumeral arthritis include female sex, obesity, family history, and a history of shoulder dislocation or fracture.^6-8

Pathophysiology

Glenohumeral arthritis can be categorized as primary or secondary.  Primary glenohumeral osteoarthritis is the more common etiology but has no known underlying cause. It is believed that the pathogenesis of arthritis results from a combination of biomechanical factors, which place abnormal stresses on the joint; genetic predisposition; and environmental factors.⁹ A progressive loss of articular cartilage develops. Articular cartilage normally functions as a shock absorber and in facilitating motion of the joint by reducing friction. Over time, classic signs of glenohumeral arthritis on radiographs emerge, including subchondral sclerosis and cysts, joint space narrowing, osteophytes, and posterior glenoid wear.^10-12 In contrast, secondary glenohumeral osteoarthritis results from a specific cause or predisposing factor. One such cause is osteonecrosis, which results from a disruption of the subchondral blood supply to the humeral head, leading to collapse of the articular surface.^13,14 Common etiologies of osteonecrosis include corticosteroid use, sickle cell disease, and heavy alcohol use.^13,14  Degenerative joint changes, can occur as sequelae of trauma, such as dislocation and proximal humerus fracture.¹⁵ Subluxation and dislocation may cause osteochondral fracture, subchondral bone injury, and damage to the glenohumeral articular cartilage. Similarly, initial fracture displacement or malunion (the healing of bone in an abnormal position) can result in accelerated joint degeneration.⁶ Lastly, secondary glenohumeral arthritis can result from inflammatory causes, such as rheumatoid arthritis, or postsurgical changes.⁶ Notably, intra-articular pain pumps, which were sometimes used following arthroscopic shoulder surgery, were a common cause of cartilage damage before this practice was stopped.¹⁶

History

Patients with osteoarthritis typically present with shoulder pain that localizes deep and posterior in the glenohumeral joint. The pain worsens with range of motion of the shoulder and may also be present at night. Some patients may report difficulty sleeping due to significant nighttime pain. Along with the pain, patients often report limited range of motion in all planes, and significant difficulties performing activities of daily living. Later in the course of the disease, mechanical symptoms, such as crepitus, catching, or locking, may be present. These mechanical symptoms may be suggestive of a bony fragment that is partially detached or in the glenohumeral joint,^17,18 or bone-on-bone contact as the cartilage wears out completely. In addition, it is important to note any previous intervention, including physical therapy, non-steroidal anti-inflammatory drugs (NSAIDs), or corticosteroid injections, as this knowledge can better inform current management. Lastly, relevant previous medical and social history should be obtained. This includes assessing for a history of shoulder subluxation, dislocation, or fracture; current medical conditions; and occupational or recreational activities.

Physical Examination

The physical examination for glenohumeral arthritis should include inspection, palpation, and range of motion assessment of the shoulder. Inspection involves examination of the bilateral shoulders for signs of previous surgery, fluid collection or muscle atrophy, which may be signs of a cuff tear arthropathy (glenohumeral arthritis with an associated rotator cuff tear).¹⁹ Furthermore, palpation along the joint line may elicit tenderness in the affected shoulder. As always, a thorough examination of the neck and cervical spine should be performed to rule out other causes of pain.10 Next, both active and passive range of motion should be assessed in the following planes: forward elevation, abduction, external rotation at the side, external rotation in abduction, internal rotation in abduction, and internal rotation. Notably, there may be audible and palpable crepitus, or crackling, in the joint with range of motion (video 6.1).

Significant deficits in range of motion may be present in all planes including forward elevation and external rotation (video 6.2 and video 6.3).¹⁸ In addition, patients may complain of pain during the midrange of the rotation arc. Lastly, the provocative maneuvers for rotator cuff pathology (chapter 2) should be performed to assess the integrity of the rotator cuff musculature. The usual maneuvers may not all be possible given the mechanical limitations of the arthritic shoulder. Following a comprehensive history and physical examination, radiographs of the shoulder should be obtained, which should confirm the diagnosis of glenohumeral arthritis.^10,17

Key Terminology

Crepitus

Crackling or grinding sound that occurs with motion of arthritic joints. ↵

Glenohumeral Osteoarthritis

Degenerative joint disease characterized by wear of the articular cartilage on the humeral head and glenoid. ↵

Primary Glenohumeral Osteoarthritis

Glenohumeral arthritis with no known underlying cause, believed to result from a combination of biomechanical factors, genetic predisposition, and environmental factors. ↵

Secondary Glenohumeral Osteoarthritis

Glenohumeral arthritis resulting from a specific cause or predisposing factor, such as an inflammatory condition, osteonecrosis, or a post-traumatic etiology. ↵

References

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