Shoulder Osteoarthritis: Causes, Symptoms, and Treatment

What Is Shoulder Osteoarthritis?

Shoulder osteoarthritis (OA) is a degenerative joint disease in which the smooth articular cartilage covering the ball (humeral head) and socket (glenoid) of the shoulder gradually wears away. As cartilage thins, the protective joint space narrows, bone grinds on bone, bone spurs (osteophytes) form, and the shoulder becomes painful and stiff.

Although the shoulder bears less body weight than the hip or knee, it has the greatest range of motion of any joint in the body, and end-stage arthritis there can be profoundly disabling — interfering with dressing, reaching overhead, and sleep. Shoulder OA is one of the most common reasons for shoulder replacement surgery.

This guide covers two related but distinct problems: standard (primary) glenohumeral osteoarthritis, in which the rotator cuff is intact, and rotator cuff (tear) arthropathy, a special form of shoulder arthritis that develops when a massive, long-standing rotator cuff tear leads to joint destruction. The two conditions look similar to patients but are managed very differently.

Anatomy of the Shoulder

The shoulder is a ball-and-socket joint, called the glenohumeral joint:

Humeral head: The "ball" at the top of the upper arm bone (humerus)
Glenoid: The shallow "socket" on the shoulder blade (scapula)
Articular cartilage: A smooth layer covering both surfaces
Labrum: A rim of cartilage deepening the socket
Rotator cuff: Four muscles and their tendons (supraspinatus, infraspinatus, teres minor, subscapularis) that surround the joint, center the ball in the socket, and power rotation and elevation

The rotator cuff is central to understanding shoulder arthritis. In a healthy shoulder, the cuff keeps the humeral head centered against the glenoid. When the cuff is intact, arthritis follows the familiar "bone-on-bone" pattern. When the cuff is destroyed, the mechanics of the entire joint change — and a different disease emerges.

Standard (Primary) Glenohumeral Osteoarthritis

In primary shoulder OA, the rotator cuff remains intact, but the cartilage of the ball and socket wears out. The humeral head stays centered in the glenoid, and the wear typically occurs in the back of the socket (posterior glenoid), often producing a characteristic posterior bone loss and tightness in the front of the joint.

Causes and risk factors:

Age: Most patients are over 60
Genetics: A strong heritable component to cartilage quality
Prior shoulder injury: Fracture of the humeral head or glenoid, or dislocations — "post-traumatic OA"
Prior shoulder surgery: Particularly older instability repairs that overtightened the joint
Avascular necrosis: Loss of blood supply to the humeral head (from steroids, alcohol, fracture)
Inflammatory arthritis: Rheumatoid and other inflammatory conditions damage cartilage

Rotator Cuff (Tear) Arthropathy

Cuff tear arthropathy (CTA) is a distinct and more advanced pattern of shoulder destruction. It develops when a massive, irreparable rotator cuff tear goes untreated for years. Without the cuff to hold the humeral head down and centered, the unopposed deltoid muscle pulls the head upward. The humeral head migrates superiorly and begins to grind against the underside of the acromion (the bony roof of the shoulder).

This abnormal contact produces a cascade of changes:

Upward (superior) migration of the humeral head on X-ray
Rounding and erosion of the greater tuberosity and acromion ("acetabularization" — the acromion forms a false socket)
Collapse and arthritis of the humeral head
Joint instability and weakness

Pseudoparalysis: Some patients with CTA lose the ability to actively raise the arm overhead at all, even though the joint can be moved passively. The arm simply shrugs because the deltoid cannot substitute for the missing cuff in a joint that is no longer centered.

The key distinction: standard OA is a cartilage problem in a balanced joint, while cuff tear arthropathy is a cartilage problem in an unbalanced joint that has lost its rotator cuff. This difference drives which surgery is appropriate — anatomic versus reverse replacement (see below).

Symptoms

Both forms of shoulder arthritis share core symptoms:

Deep, aching shoulder pain — often felt in the back of the shoulder, worsening with activity and at the extremes of motion
Stiffness and lost range of motion — difficulty reaching overhead, behind the back (fastening a bra, reaching a wallet), or across the body
Crepitus — grinding, clicking, or catching with movement
Night pain — one of the most common and disabling features; lying on the affected shoulder is often impossible
Weakness — particularly prominent in cuff tear arthropathy

Features that point toward cuff tear arthropathy specifically:

Marked weakness with overhead activity
Inability to actively elevate the arm despite full passive motion (pseudoparalysis)
A sensation of the shoulder "riding up" or shrugging when attempting to lift

Diagnosis

Physical examination:

Range of motion testing (active versus passive — a large gap suggests cuff involvement)
Crepitus with rotation
Rotator cuff strength testing (external rotation, lift-off, and elevation strength)
Assessment for pseudoparalysis

X-ray: Standing shoulder X-rays are the cornerstone of diagnosis:

Joint space narrowing — direct measure of cartilage loss
Osteophytes — especially an inferior humeral head "goat's beard" spur in primary OA
Subchondral sclerosis and cysts
Superior migration of the humeral head with a narrowed acromiohumeral interval — the radiographic signature of cuff tear arthropathy

MRI: Used when the status of the rotator cuff must be clarified. MRI shows cartilage loss, the size and reparability of any cuff tear, and the degree of muscle atrophy and fatty infiltration — all critical to surgical planning.

CT scan: Frequently obtained before surgery to assess glenoid bone loss and version (the tilt of the socket), which guides implant selection and sizing.

Treatment

Conservative Management (First-Line)

Most patients begin with non-surgical care, which is identical for both forms early on:

Activity modification: Avoiding aggravating overhead and behind-the-back motions
Physical therapy: Gentle range-of-motion and periscapular strengthening to maintain function; in cuff tear arthropathy, "deltoid-centric" programs train the deltoid to compensate
NSAIDs: Ibuprofen, naproxen, or celecoxib for pain and inflammation
Acetaminophen: For breakthrough pain
Heat and ice: Heat before activity to loosen the joint; ice afterward to calm inflammation
Corticosteroid injections: Intra-articular injection provides temporary relief (weeks to a few months) and can confirm the joint as the pain source
Hyaluronic acid injections: Limited evidence in the shoulder; sometimes used off-label

Surgical Treatment

When pain and stiffness no longer respond to conservative care, surgery is highly effective — but the choice of operation depends entirely on the rotator cuff:

Anatomic total shoulder replacement (TSA): The gold standard for standard glenohumeral OA with an intact, functioning rotator cuff. Both the ball and socket are resurfaced with implants that mirror normal anatomy, relying on the intact cuff to power and stabilize the joint. See the total shoulder replacement surgical guide for what to expect on surgery day.
Reverse total shoulder replacement (rTSA): The procedure of choice for cuff tear arthropathy and for arthritis with an irreparable cuff. By reversing the ball-and-socket geometry, it allows the deltoid muscle to raise the arm without a functioning cuff — restoring overhead function even in shoulders that could not previously lift. See the reverse shoulder arthroplasty surgical guide for full detail.
Hemiarthroplasty: Replacement of only the humeral head, used in select younger patients or specific bone-loss situations; less common today.

Choosing between anatomic and reverse replacement is the single most important surgical decision in shoulder arthritis, and it is determined by the integrity of the rotator cuff — the very distinction at the heart of this guide.