Painful arc

Supraspinatus tendinitis (also known as impingement syndrome and painful arc syndrome).

The classical sign of supraspinatus tendinitis is the painful arc on resisted abduction between 60 and 120 degrees when the inflamed tendon presses against the acromium - outside of this range, abduction is painless. Abduction with the arm in full external rotation is usually without pain throughout the entire range of movement.

The painful arc may also characterise a partial tear of the tendon. Weakness of resisted abduction is usually present when the tear is 2cm or more.

Disorders of the shoulder are extremely common, with reports of prevalence ranging from 30% of people experiencing shoulder pain at some stage of their lives up to 50% of the population experiencing at least one episode of shoulder pain annually. In addition to the high incidence, shoulder dysfunction is often persistent and recurrent, with 54% of sufferers reporting ongoing symptoms after 3 years (1)

Impingement syndrome can usually be diagnosed by history and examination

• shoulder x-rays may reveal joint pathology including acromioclavicular arthritis, variations in the acromion, and calcification
• ultrasound, arthrography and MRI can be used to detect rotator cuff muscle pathology

Treatment

• conservative treatment includes rest, cessation of painful activity, and physiotherapy
  • NSAIDs and analgesia may be of benefit
• corticosteroid and local anaesthetic injections may be used for persistent impingement syndrome.
• surgical treatment
  • may be done arthroscopically or as open surgery
    • impinging structures may be removed in surgery, and the subacromial space may be widened by resection of the distal clavicle and excision of osteophytes on the under-surface of the acromioclavicular joint
    • if surgical treatment is undertaken then damaged rotator cuff muscles can be surgically repaired.

Notes:

• over 90% of tendinopathies have no inflammation, thus the term tendinosis is more appropriate than tendinitis for most diagnoses (1)
• rotator cuff impingement syndrome
  • rotator cuff muscle tendons pass through a narrow space between the acromion process of the scapula and the head of the humerus
    • symptoms include pain, weakness and loss of motion
    • anything which causes further narrowing of this space can result in impingement syndrome
      • causes include
        • bony structures such as subacromial spurs (bony projections from the acromion), osteoarthritic spurs on the acromioclavicular joint, and variations in the shape of the acromion
        • thickening or calcification of the coracoacromial ligament
        • loss of function of the rotator cuff muscles, due to injury or loss of strength, may cause the humerus to move superiorly, and cause impingement
        • inflammation and subsequent thickening of the subacromial bursa
      • however within the rotator cuff, supraspinatus is the cuff tendon most liable to injury. It is the most exposed of the tendons - running over the top of the shoulder under the anterior edge of the acromion and the adjacent acromioclavicular joint - and also has a relatively poor arterial blood supply near to it's insertion into the greater tuberosity. Consequently, `supraspinatus' is often used synonymously with `rotator cuff' when describing lesions of this area
        
        
  • clinical features
    • pain, weakness and loss of motion are the most common symptoms reported
      • pain is exacerbated by overhead or above-the-shoulder activities
      • a frequent complaint is night pain, often disturbing sleep, particularly when the patient lies on the affected shoulder
    • onset of symptoms may be acute, following an injury, or insidious, particularly in older patients, where no specific injury occurs
    • there may be a grinding or popping sensation during movement of the shoulde
    • range of movement may be limited by pain
    • a painful arc of movement may be present during forward elevation of the arm from 60° to 120°
    • passive movement at the shoulder will appear painful when a downwards force is applied at the acromion but the pain will ease once the downwards force is removed
      
      
  • click here for a video of examination of the rotator cuff and possible impingement

Reference:

• 1) Br J Sports Med. 2009 Apr;43(4):259-64
• 2) Fongemie AE, Buss DD, Rolnick SJ. Management of shoulder impingement syndrome and rotator cuff tears.Am Fam Physician. 1998 Feb 15;57(4):667-74, 680-2.