Anatomy of the shoulder joint

• The humerus, glenoid, scapula, acromion, clavicle and surrounding soft tissues make up the shoulder.
• There are three significant articulations:
  • The sternoclavicular joint
  • The acromioclavicular joint
  • The glenohumeral joint. (The glenohumeral joint is the most commonly dislocated major joint in the body).
• Ligaments and surrounding musculature, including the rotator cuff muscles, contribute to shoulder joint stability.
• The rotator cuff is composed of the 4 muscles:
  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis
• These muscles help with internal and external rotation of the shoulder and also depress the humeral head against the glenoid.

Epidemiology

Shoulder pain is the third most common cause of musculoskeletal consultation in primary care.

• 1% of adults consult their GP with new shoulder pain each year.
• Self-reported prevalence of shoulder pain is between 16% and 26%.

Risk factors

• Physical factors related to occupation including repetitive movements and exposure to vibration from machine tools.
• Psychosocial factors related to work may also be risk factors for shoulder pain including stress, job pressure, social support and job satisfaction. However, in a systematic review, results were not consistent.
• Athletes that are involved in throwing sports, sports that involve repetitive arm movements or high-impact contact sports, e.g. rugby and swimming/diving, are prone to shoulder pain.
• Occupations particularly prone to shoulder pain syndromes include:
  • Cashiers
  • Garment makers
  • Bricklayers/construction workers
  • Pneumatic tool operators
  • Welders
  • Meat/food-processing workers
  • Hairdressers
  • Plasterers
  • Assembly/production line workers
  • Workers using keyboards for long periods, e.g. IT, secretarial

Causes of shoulder pain

• Intrinsic shoulder pain
  • Rotator cuff disorders: rotator cuff tendinopathy, impingement (trapping of rotator cuff tendon, particularly supraspinatus, in subacromial space), subacromial bursitis, rotator cuff tears, calcific tendonitis
  • Glenohumeral disorders: capsulitis ('frozen shoulder'), arthritis
  • Acromioclavicular disease
  • Infection (rare)
  • Traumatic dislocation
• Extrinsic shoulder pain
  • Referred pain: neck pain, myocardial ischaemia, referred diaphragmatic pain (e.g. gallbladder disease, subphrenic abscess)
  • Polymyalgia rheumatica
  • Malignancy: apical lung cancers, metastases

Assessment of shoulder pain

When assessing shoulder pain, take a history and perform an examination with these questions in mind:

• Is the pain arising from the shoulder, neck or elsewhere?
• Are there any red flag symptoms/signs (see below)?
• Is the pain localised to the acromioclavicular joint? If yes, there is acromioclavicular joint disease.
• Is there global pain and restriction of all active and passive movements? If yes, this suggests glenohumeral joint disorder (either frozen shoulder or arthritis).
• Is there pain on abduction with thumb down, worse against resistance and/or is there a painful arc? If yes, this suggests a rotator cuff disorder. History

Points to cover in the history include:

• The nature of the pain including:
  • How the pain started
  • Any specific injury
  • Whether it is acute or chronic
  • Any impact on function/activities of daily living
  • Whether the pain is on the side of the dominant hand
  • Whether there is pain at rest or on movement
  • Whether there is night pain that affects sleep
• Any associated pain, for example, neck, chest or other upper limb or joint pain.
• Any history of shoulder pain/instability/dislocation.
• The patient's occupation.
• The patient's sporting activities.
• Any signs or symptoms of systemic illness.
• Past medical history (particularly any history of diabetes, ischaemic heart disease, cancer).
• Drug history and adverse drug reactions.

Pain from generalised capsulitis is felt at the outer aspect of the upper arm or deltoid region and may keep the patient awake. Anterior capsulitis usually causes well localised pain felt anteriorly over the upper biceps insertion. Rotator cuff/supraspinatus pain is also felt in the upper aspect of the arm or deltoid region and will be accompanied by a painful arc.

Examination

Remember 'Look, Feel, Move'.

• Examine the neck, axilla and chest wall.
• Examine the cervical spine and assess range of movement.
• Inspect the shoulders looking for swelling, wasting, deformity. Always compare both sides.
• Palpate the sternoclavicular, acromioclavicular and glenohumeral joints. Look for tenderness, swelling, warmth and crepitus.
• Assess the power, stability and range of movement (active, passive and resisted) in both shoulders.
• Look for a painful arc (pain between 70 and 120 degrees of abduction).
• Test passive external rotation (reduced in frozen shoulder). With the elbow held into the side, turn the arm outwards as far as possible.
• Perform the 'drop arm test': passively abduct the patient's shoulder. Then ask the patient to lower the abducted arm slowly to the waist. This can identify a rotator cuff tear. They may be able to lower the arm slowly to 90 degrees because this uses mostly the deltoid muscle but below 90 degrees, the arm will drop to the side.
• Perform the 'cross-arm test': this isolates the acromioclavicular joint. Ask the patient to raise the arm to 90 degrees straight in front of them. Then ask them to adduct the arm across the chest. If there is an acromioclavicular joint problem, there will be pain in the area of the joint.
• vestigations
• Blood tests and radiology are generally only necessary if there are 'red flag' symptoms/signs.
• Plain X-ray of shoulder may reveal relevant changes in the glenohumeral or acromioclavicular joints.
• If referred neck pain is suspected then cervical spine x-rays may be helpful.
• More detailed imaging investigations such as ultrasonography and MRI scanning are best reserved for further investigation in secondary care.
• If there are relevant 'red flags' to indicate systemic illness then consider blood tests including full blood count, ESR/CRP and further investigations such as chest X-ray as appropriate.

Management

• Corticosteroid injections may be of limited short-term benefit for shoulder pain.
• Physiotherapy may be effective for shoulder pain in some cases but that further high quality trials are needed.
• There is not enough evidence to say whether acupuncture works to treat shoulder pain or if it is harmful.

Specific management points are discussed under the individual disorders below.

Rotator cuff disorders

Rotator cuff tendinopathy

• The most common cause of shoulder pain.
• There may be a history of repetitive movement or heavy lifting.
• A painful arc may be present with painful and/or restricted active movement and full but painful passive movement.
• Evidence shows that physiotherapy and steroid injections may be equally helpful in the short term.
• Injections may be repeated if the initial response is good.

Rotator cuff tears

• Most common in people over 40 years.
• In younger people, tears are usually due to trauma; in older people, there is often a chronic impingement syndrome that leads to rupture of the cuff. In impingement syndrome, the tendons of the rotator cuff are 'caught' between the humerus and coracoacromial arch when the arm is abducted.
• The history normally points to the diagnosis.
• Tears can be minor/partial or full. Partial tears may be difficult to differentiate from tendinopathy as clinical findings are similar. The 'drop arm test' can be used to detect a large/complete tear.
• Physiotherapy and steroid injections may be helpful for minor tears. However, there is no proven harm or benefit from steroid injection if a rotator cuff tear is present so they should be avoided if there is a positive drop arm test.
• Suspected acute, severe tears of the rotator cuff tendons may benefit from early referral for orthopaedic input.
• Surgical treatment usually involves rotator cuff tendon repair ± subacromial decompression, either through open surgery or arthroscopically.
• Calcific tendonitis may respond to extracorporeal shock wave lithotripsy and NICE have recently issued guidance on this.

Glenohumeral disorders

Please also refer to frozen shoulder article.

• In frozen shoulder or glenohumeral arthritis, pain is felt deep within the joint. There is restricted shoulder movement (all movements) which affects activities of daily living.
• Where osteoarthritis is suspected then simple analgesia is of benefit.
• Adhesive capsulitis can take up to 3 years to improve, particularly in diabetic patients.
• Steroid injection and/or physiotherapy may be helpful.

Acromioclavicular disease

• The usual causes are trauma and osteoarthritis.
• There may be pain, tenderness and swelling around the acromioclavicular joint.
• There is restriction of passive, horizontal adduction of the shoulder, with the elbow extended across the body
• Acromioclavicular injury usually responds to rest and simple analgesia, unless there is significant disruption of the joint, in which case orthopaedic referral is necessary.

Criteria for referral to secondary care

Consider referral for orthopaedic or other appropriate specialist review for people who present with shoulder pain in the following circumstances:

• Pain and significant disability for > 6 months despite appropriate conservative management
• History of joint instability
• Acute severe post-traumatic acromioclavicular pain
• Suspected unreduced dislocation
• Diagnostic uncertainty
• Red flags indicating systemic illness or condition requiring urgent investigation

Prognosis

• This depends on the underlying cause.
• Studies in primary care show that one year after a first consultation, 40-50% of patients report that their symptoms have persisted or recurred.
• Poor recovery is associated with increasing age, severe symptoms, recurrent symptoms at presentation, a restricted range of passive abduction with concomitant neck pain.
• Mild trauma or overuse before the onset of pain, early presentation and acute onset are favourable prognostic factors.