The Shoulder Capsule and How the Condition Develops

The shoulder is a ball-and-socket joint between the head of the humerus and the shallow glenoid of the shoulder blade. The capsule that encloses it is normally loose and elastic; this laxity is what allows the arm to move through such a wide range.

In adhesive capsulitis the capsule first becomes inflamed and then fibrotic (a scar-like stiffening). It thickens and contracts, and the loose inferior recess (axillary pouch) is obliterated. Joint volume falls markedly and the shoulder becomes mechanically locked.

Frozen shoulder is therefore not muscle weakness or a tendon tear, but a disease of the capsule itself. The patient cannot lift the arm not because the strength is lacking, but because the capsule will not allow it.

Primary and Secondary Frozen Shoulder

• Primary (idiopathic) frozen shoulder: Begins spontaneously with no identifiable cause. This is the most common type
• Secondary frozen shoulder: Linked to a known trigger — shoulder trauma, fracture, prolonged immobilisation after shoulder surgery, rotator cuff disease
• Associated with systemic disease: Diabetes (the strongest association), thyroid disease (hypo- and hyperthyroidism), Parkinson's disease, cardiovascular disease
• Frozen shoulder is markedly more common in people with diabetes than in the general population; in these patients the course may be more stubborn and the response to treatment slower

Stages of the Condition

Frozen shoulder progresses through four stages. The stage a patient is in directly determines the treatment, which makes staging the most important part of the treatment plan.

• Stage 1 — Painful onset (0 - 3 months): Insidious shoulder pain; range of movement is still largely preserved. Night pain is prominent
• Stage 2 — Freezing (3 - 9 months): The most painful phase; range of movement is lost rapidly. External rotation (turning the arm outwards) is particularly restricted
• Stage 3 — Frozen (9 - 15 months): Pain begins to settle but stiffness is at its worst. Everyday tasks become very difficult
• Stage 4 — Thawing (15 - 24 months): Range of movement is gradually regained. Full recovery may take 2 - 3 years

Symptoms

• Deep, dull shoulder pain: Radiating to the deltoid insertion and the upper outer arm
• Night pain: Inability to lie on the affected side; pain that wakes the patient. The most typical complaint of the early stage
• Progressive loss of movement: External rotation is lost first, followed by abduction (lifting the arm sideways) and internal rotation
• Difficulty with daily tasks: Combing hair, fastening a bra behind the back, reaching a back pocket, putting on a jacket, reaching a high shelf
• Equal restriction of active and passive movement: Neither the patient nor the examining doctor can move the arm through its full range — the distinguishing sign of the diagnosis
• Strength is generally preserved: The restriction comes from stiffness, not weakness
• Compensatory movement: The patient begins to use the shoulder blade and trunk to lift the arm

Diagnosis

The diagnosis is largely clinical. Age, the duration and course of symptoms, associated conditions (particularly diabetes and thyroid disease) and any previous shoulder injury or surgery are reviewed.

Active and passive ranges of movement are measured separately. Marked restriction of passive external rotation is the single most valuable sign of adhesive capsulitis; in a rotator cuff tear, passive movement is usually preserved while active movement is restricted.

Plain radiographs are normal in frozen shoulder; their purpose is to exclude other causes such as arthritis, calcific tendinitis or fracture. MRI is not required for the diagnosis but is requested if associated rotator cuff pathology is suspected; it may show capsular thickening and obliteration of the axillary recess. Blood glucose and thyroid function should be checked in every patient diagnosed — underlying diabetes or thyroid disease may come to light for the first time in this way.

Non-operative Treatment

Frozen shoulder is treated primarily without surgery, and the great majority of patients recover without an operation. Treatment is tailored to the stage: in the early stage the priority is pain control; in the later stages it is regaining movement.

• Patient education: Understanding that the condition is long but usually ends well markedly improves adherence to treatment
• Analgesics and anti-inflammatory medication (NSAIDs): Particularly in the early painful stage
• Intra-articular corticosteroid injection: When given early (within the first 6 months) it markedly reduces pain and makes physiotherapy easier. Ultrasound or fluoroscopic guidance improves accuracy
• Hydrodilatation (arthrographic distension): Saline, corticosteroid and local anaesthetic are injected under pressure to stretch the capsule. Effective in selected patients
• Physiotherapy and stretching: The foundation of treatment. Gentle, regular stretching within the limit of pain. Aggressive stretching that markedly increases pain can make the condition worse
• Home exercise programme: Short stretching sessions several times a day — pendulum exercises, finger walking up a wall, towel stretch for internal rotation
• Heat before exercise: Warming the muscles and capsule makes stretching more effective
• Control of diabetes and thyroid disease: Blood glucose control directly affects the response to treatment
• Corticosteroid injection combined with physiotherapy is superior to either treatment alone

Surgical Options

Surgery is considered when pain and restricted movement continue to affect daily life significantly despite at least 4 - 6 months of consistent non-operative treatment. Only a small proportion of patients with frozen shoulder need surgery.

• Arthroscopic capsular release: The preferred method today; the contracted parts of the capsule are divided in a controlled way
• Manipulation under anaesthesia (MUA): With the patient asleep, the arm is moved in controlled steps to stretch the capsule; used alone or in addition to arthroscopy
• Both procedures only succeed when followed by early, intensive physiotherapy; surgery on its own is not enough

Expected Outcomes

When managed correctly, frozen shoulder generally has a good outcome. Most patients regain a pain-free, functional shoulder within 1 - 3 years with non-operative treatment. Some are left with a mild permanent restriction, which usually does not affect daily life.

After surgery, range of movement usually improves markedly in the first weeks; keeping those gains depends entirely on adherence to rehabilitation. Recovery may be slower and recurrence more likely in patients with diabetes.

Risks Specific to Non-operative Treatment

• Duration: Even with treatment the condition may last 1 - 3 years, affecting work and social life
• Permanent restriction: Some patients are left with a mild permanent restriction, particularly of external rotation
• Temporary rise in blood glucose after corticosteroid injection (may last several days in patients with diabetes)
• Adverse effects of repeated corticosteroid injections on tendon tissue
• Aggressive stretching beyond the pain limit: Can increase inflammation and worsen the condition

Surgical Risks — Common

• Postoperative pain and swelling: May be marked in the first days because the capsule has been released
• Temporary change in sensation: Numbness and weakness of the arm from the interscalene block (usually resolves in 12 - 24 hours)
• Superficial portal infection (uncommon; usually treated with antibiotics)
• Temporary effects of anaesthesia such as nausea and dizziness

Surgical Risks — Less Common

• Recurrence of stiffness: The most important risk. If physiotherapy is not maintained, the movement gained can be lost within weeks. The risk is markedly higher in patients with diabetes
• Axillary nerve injury: May occur during release of the inferior capsule; causes deltoid weakness and loss of sensation over the outer shoulder (rare)
• Humeral fracture: Particularly with manipulation under anaesthesia, in patients with osteoporosis and in older patients
• Rotator cuff tear: May result from excessive force during manipulation
• Shoulder dislocation or labral injury: During manipulation (very rare)
• Deep joint infection (under 1%): Requires revision surgery and prolonged antibiotics
• Complex regional pain syndrome (CRPS): Rare; presents with pain, swelling and hypersensitivity

Risk Factors

• Diabetes: Markedly increases both the risk of developing the condition and the risk of recurrence; outcomes are worse when diabetes is poorly controlled
• Thyroid disease (hypo- and hyperthyroidism)
• A shoulder immobilised for a long period (after fracture or surgery)
• Advanced age and osteoporosis (fracture risk during manipulation)
• Poor adherence to physiotherapy — the most common cause of surgical failure
• Smoking
• A previous frozen shoulder on the other side

Contact Your Doctor Immediately If

• Pain or swelling suddenly increases
• You have a temperature above 38 °C
• There is discharge, a bad smell or opening of the wound
• Numbness, tingling or weakness in the arm or hand is progressing
• You cannot lift the arm or the shoulder suddenly looks deformed
• The movement gained after surgery is rapidly being lost

Long-term Outcomes

When correctly treated, frozen shoulder has high patient satisfaction. Most patients achieve a pain-free, functional shoulder with non-operative treatment. In those who undergo surgery, range of movement usually improves markedly within the first weeks.

A mild permanent restriction, particularly of external rotation, is possible; in most patients it does not affect daily life. Recurrence in the same shoulder is rare, but the risk of developing it in the other shoulder is higher than in the general population. Keeping diabetes and thyroid disease under control is a key determinant of long-term success.