Intrinsic shoulder pain

A thorough history and examination are key to diagnosing shoulder pain, says Dr Julian Spinks.

Diagnosing shoulder pain can be difficult due to the complexity of the shoulder joint
Diagnosing shoulder pain can be difficult due to the complexity of the shoulder joint

Shoulder pain is a common presentation in primary care. However, diagnosing and managing shoulder pain can be difficult because of the complexity of the structure and function of the shoulder.

There are nearly 30 muscles involved in shoulder function, together with four articulations. These are glenohumeral, acromioclavicular, sternoclavicular and scapulothoracic. There are also a number of other structures and organs that can cause pain felt at the shoulder.

The most common causes of shoulder pain and stiffness are degenerative and inflammatory arthritis, adhesive capsulitis (frozen shoulder) and rotator cuff pathology, tendinitis and bursitis. Multiple pathologies occur in many patients.

History
A general history may reveal co-morbidities associated with adhesive capsulitis such as diabetes, or a previous stroke which commonly predisposes to shoulder pain. Red flags include significant trauma, systemic upset and previous cancer.

Younger patients are more likely to have disorders involving the rotator cuff and acromioclavicular joints. Osteoarthritis is mostly found in those aged over 60 years. Adhesive capsulitis is most common in the 40-65 age range.

If the patient's occupation or sporting history includes repetitive movements that involve moving the arm above shoulder level they are likely to have rotator cuff tendinitis. Trauma could indicate rotator cuff tears, dislocations and subluxations at the glenohumeral or acromioclavicular joints.

The onset of pain can also help determine the cause. Adhesive capsulitis has a slow onset and progresses through three characteristic phases. During the first 10-36 weeks there is pain and stiffness, particularly at night. From four to 12 months after onset the pain reduces but the stiffness remains. Finally, from 12 months to three years there is gradual resolution of stiffness. By contrast, tears and tendinitis have a more rapid onset.

Rotator cuff disorders often occur in the non-dominant arm of sedentary workers. Night pain and inability to lie on the affected side occur in rotator cuff tears. Instability suggests dislocation or subluxation. Any distant joint involvement should be noted as this may point to degenerative or inflammatory arthritis.

Examination
The examination should include inspection of the skin, bony contours and musculature. Any swelling or deformity should be noted. The sternoclavicular, acromioclavicular and glenohumeral joints should be examined for tenderness, swelling, crepitus and warmth. The range of movement, power and stability should be examined for passive, active and resisted movements.

It is important to look for evidence of neurological damage including winging of the scapula, and sensory or motor deficits.

In rotator cuff disorders, active and resisted movements are painful and often restricted while passive movements are full but painful. In adhesive capsulitis, passive movement is also restricted.

Some signs point to particular diagnoses. The presence of pain at 70-120 degs active abduction suggests supraspinatus tendinitis. Greater restriction of external than internal rotation or abduction suggests adhesive capsulitis. Pain on resisted elbow flexion points to bicipital tendinitis.

Pain and restricted shoulder abduction occur in acromioclavicular strain. Pain on resisted internal rotation suggests subscapularis tendinitis and on external rotation indicates infraspinatus tendinitis.

A positive drop-arm test is a red flag sign. In this the arm is slowly lowered to the waist from abduction. Inability to do this smoothly suggests a significant rotator cuff tear.

Investigation
In many cases of shoulder pain, diagnosis is clinical and investigations are not required. If inflammatory joint disease is suspected then ESR, CRP and immunological tests are indicated. A plain shoulder X-ray can identify calcified tendons, dislocations and subluxations. MRI scanning may be needed in complex cases.

Treatment
The aim of treatment is to reduce pain and enable patients to rehabilitate. For acromioclavicular disorders, analgesia and rest are the primary treatment with steroid injections reserved for persistent cases.

Degenerative arthritis is predominately treated with analgesia, NSAIDS and physiotherapy. In severe cases, shoulder joint replacement may be needed. If there is an inflammatory arthritis, referral for specialist assessment is warranted.

In rotator cuff disorders, initial analgesia with rest should be followed by a return to activity within the limits defined by the onset of pain.

Physiotherapy has been shown to be of benefit in the short term. Steroid injections into the subacromial space provide short-term pain relief and can help with rehabilitation.

However, a study has shown that patients given steroid injections alone were more likely to reconsult than those offered physiotherapy. A small number of patients may require referral for surgical repair.

Treatment for adhesive capsulitis depends on the stage. During the first phase, analgesia and physiotherapy are both effective. Movement should be restricted.

Early use of intra-articular steroid injections may help. During the adhesive phase, steroid injections are not indicated but analgesia and more aggressive stretching are beneficial.

In patients who fail to respond, or are intolerant of the pain, referral for manipulation under anaesthesia or surgical release should be considered.

Dr Spinks is a GP with an interest in urinary continence in Strood, Kent, and NICE guideline development group member

Key Points

  • Rotator cuff disorders, adhesive capsulitis, arthritis and dislocation/subluxation are the most common intrinsic causes of shoulder pain.
  • Slow onset and three clinical phases are typical in adhesive capsulitis.
  • Quicker onset and inability to lie on the affected side is found in rotator cuff disease.
  • Red flags include systemic upset, significant trauma, previous cancer and a positive drop-arm test.
  • Treatment for all conditions includes analgesia and physiotherapy. Steroid injections are sometimes indicated but the research evidence is weak.

References

  • Mitchell C, Adebajo A, Hay E et al. Shoulder Pain: diagnosis and management in primary care. BMJ 2005; 331(7525): 1,124-8.
  • Dias R, Cutts S, Massoud S. Frozen Shoulder BMJ 2005; 331; 1,453-6.
  • Buchbinder R, Green S, Youd J M. Corticosteroid injections for shoulder pain. Cochrane Database Syst Rev. 2003; (1): CD004016.

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