Frozen shoulder (adhesive capsulitis) is a common benign shoulder disorder. There is thickening and scarring of the joint capsule and stiffening of the joint causing nocturnal pain and painful and restricted movement.
The diagnosis is based on restricted active and passive movements, pain in the shoulder area and normal shoulder x-ray.
The prognosis is very favourable but in some cases it may take several years for symptoms to resolve spontaneously.
Surgical treatment may sometimes be considered to improve a significantly restricted range of movement if symptoms continue beyond the normal course of the disorder.
Prevalence
The lifetime prevalence of frozen shoulder is estimated at 2-5%, and it is most common in people aged 40-60 years 6.
Diabetes, hypothyroidism, hypercholesterolaemia and mild shoulder injury would appear to be associated with frozen shoulder but a true causal relationship is yet to be shown 2.
In people with diabetes, the lifetime risk of frozen shoulder and of bilateral frozen shoulder is increased, 10-20% 2.
Recurrence of the disorder in the same shoulder is very rare.
The ultimate cause of the disorder remains unclear.
Signs and symptoms
The clinical course can be divided into four stages but there is individual variation.
Painful stage (from a few weeks to a few months): pain at rest, nocturnal pain and pain on movement. Active movement may be restricted due to pain but passive movement is still normal.
Freezing stage (from a few months to about one year): progressively restricted active and passive movements; in the early stage, external rotation, in particular, is restricted. Nocturnal pain and pain on movement.
Frozen stage (from a few months to more than one year): active movement restricted and passive movement, in particular, significantly restricted. Pain often decreases at this stage.
Thawing stage: stiffness decreases, and in most patients this will lead to even completely restored normal ranges of motion. The time from the beginning of symptoms to spontaneous recovery of movement is 6-24 months but in some cases movement has not improved even after several years of symptoms.
Most typically, shoulder pain has a gradual onset but in some cases it may be preceded by mild injury.
The symptoms and their severity may vary. In the most severe cases, there is constant shoulder pain aggravated by movement.
Workup
Clinical assessment
Patients with shoulder symptoms should always be examined with their upper body naked.
The ranges of active shoulder motion (flexion, abduction, internal and external rotation) should be examined, as well as ranges of passive motion if active motion is restricted.
In a frozen shoulder, both active and passive ranges of motion are restricted. There are no generally applicable diagnostic criteria for the angles of movement. It is therefore important to compare (passive) ranges of motion to the unaffected side. Passive external rotation, in particular, is restricted and typically painful when tested.
Testing of rotator cuff muscle strength means testing the strength against resistance, not pain. The strength of the infraspinatus and supraspinatus muscles (picture 1) should be examined separately (picture 2).
Radiological examination
Shoulder x-ray is the primary form of imaging in patients with shoulder pain. It should be done no later than one month from the onset of symptoms. A frozen shoulder looks normal on x-ray (picture 3).
Diagnosis
The diagnosis is based on shoulder pain, (increasingly) restricted movement and normal x-ray.
At the pain stage, the diagnosis is often uncertain but it can usually be specified further at the frozen stage.
Differential diagnosis
As frozen shoulder may develop after mild injury, the possibility of traumatic rotator cuff tendon rupture should be kept in mind at the initial stage Traumatic Tendon Problems of the Shoulder.
After the initial pain stage, other differential diagnostic alternatives include rotator cuff disorders Non-Traumatic Tendon Problems of the Shoulder, cervical causes, infections (erythema, fever, oedema) and tumours (palpable mass, oedema).
At the freezing or frozen stages, differential diagnostic alternatives include primarily osteoarthritis (picture 4) and rotator cuff arthropathy (picture 5).
Treatment
As the prognosis of frozen shoulder is highly favourable, treatment is normally conservative 15.
Patient information on the course and favourable prognosis of the disorder
Analgesics
A few visits to a physiotherapist (to check the position and movements of the shoulder girdle and for exercises to maintain ranges of movement)
Attention to work ergonomic issues
A subacromial glucocorticoid-anaesthetic injection can be tried for severe pain. Intra-articular glucocorticoid injections have traditionally been used but they have not proved more effective than subacromial injections 4.
At the initial pain stage (when passive ranges of movement are still intact), the diagnosis of frozen shoulder is still unclear and treatment is, in practice, as for non-traumatic tendon problems of the shoulder Non-Traumatic Tendon Problems of the Shoulder.
Referral criteria and surgical treatment
If shoulder movements have not improved at all during the average natural recovery time (about 1.5 to 2 years) and the patient experiences the restricted movement as a significant problem, they should be referred for assessment by an orthopaedist.
Arthroscopic capsulotomy is considered case by case even though the evidence for its true efficacy is not too strong 3.
References
Salomon M, Pastore C, Maselli F, et al. Manipulation under Anesthesia versus Non-Surgical Treatment for Patients with Frozen Shoulder Contracture Syndrome: A Systematic Review. Int J Environ Res Public Health 2022;19(15). [PubMed]
Karbowiak M, Holme T, Mirza M, et al. Frozen shoulder. BMJ 2022;377()e068547. [PubMed]
Forsythe B, Lavoie-Gagne O, Patel BH, et al. Efficacy of Arthroscopic Surgery in the Management of Adhesive Capsulitis: A Systematic Review and Network Meta-analysis of Randomized Controlled Trials. Arthroscopy 2021;37(7)2281-2297. [PubMed]
Challoumas D, Biddle M, McLean M, et al. Comparison of Treatments for Frozen Shoulder: A Systematic Review and Meta-analysis. JAMA Netw Open 2020;3(12)e2029581. [PubMed]
Rangan A, Brealey SD, Keding A, et al. Management of adults with primary frozen shoulder in secondary care (UK FROST): a multicentre, pragmatic, three-arm, superiority randomised clinical trial. Lancet 2020;396(10256)977-989. [PubMed]
Lewis J. Frozen shoulder contracture syndrome - Aetiology, diagnosis and management. Man Ther 2015;20(1)2-9. [PubMed]