Supraspinatus Anatomy, Tendinopathy, Pain and Tear Test

Supraspinatus Location

The supraspinatus is one of the 4 rotator cuff muscles that embrace the shoulder joint (the other 3 being infraspinatus, teres minor and subscapularis). It extends from the upper back surface of the shoulder blade (scapula) to the upper part of the upper arm bone (humerus).

Origin

The supraspinatus originates from the supraspinous fossa of the scapula ^[1].

Insertion

The supraspinatus inserts to the superior aspect of greater tubercle of the humerus ^[1].

Functions (Actions)

Assists the deltoid muscle in the initiation of the elevation of the arm sideways (abduction)
Stabilizes the humeral head in the shoulder joint
Reference: ^[1]

Innervation

The supraspinatus is innervated by the suprascapular nerve, which originates from the spinal nerves C4, C5 and C6 ^[1].

Blood Supply

The supraspinatus gets the blood via the suprascapular artery ^[1].

Picture 1. Supraspinatus muscle (back view)

Related anatomy:

Supraspinatus Tendinopathy

Supraspinatus tendinopathy refers to an overuse damage of the supraspinatus tendon, which can appear as:

Tendinosis: small tears within the tendon without significant inflammation
Tendonitis or tendinitis: inflammation of the tendon
Shoulder impingement syndrome: tendon thickening due to its repeat rubbing against the coracoacromial ligament above it.

Supraspinatus tendinopathy usually occurs in athletes with repetitive overhead movements and is called accordingly: tennis, pitcher’s, thrower’s or swimmer’s shoulder ^[5]. Other causes of supraspinatus tendinopathy include direct injury, age-related degeneration, calcific tendinopathy and arthritis in the shoulder joint ^[5].

Symptoms, which develop gradually, include pain in the side, front or back of the shoulder, shoulder stiffness and arm weakness. The pain is aggravated by reaching backward or over the head and by sleeping on the affected side ^[5]. Signs include tenderness at the top-side of the shoulder and pain during raising the arm.

A doctor can make a diagnosis on the basis of the symptoms and signs alone or with the help of magnetic resonance imaging (MRI), sonoelastography or arthroscopy (endoscopic investigation of the shoulder joint).

Treatment can include:

Rest from all painful activities
Ice packs several times a day for 15 minutes in the first 48 hours
Nonsteroidal anti-inflammatory drugs (ibuprofen, naproxen)
Steroid injections (in severe pain)
Stretching and strengthening exercises to prevent muscle wasting (atrophy)

Supraspinatus Tear

Supraspinatus tear often begins as a strain and then a partial tear, which can–with repeated injuries–progresses to a full thickness tear. Most tears occur at the muscle attachment to the upper arm bone.

Causes

Acute strain or tear can be caused by lifting a heavy object quickly, falling on an outstretched arm, breaking the collarbone or dislocating the shoulder ^[2].
The degenerative tear occurs gradually in sports or jobs with repetitive arm movements (baseball, tennis, rowing, weightlifting, painting) or with age due to poor blood supply and bone spurs ^[2].

Risk factors for supraspinatus tear include age over 40, smoking and multiple steroid injections ^[4].

Symptoms

Pain and weakness in the shoulder when raising the arm sideways and when sleeping on the affected side; NOTE: the pain can be mild and can completely disappear on its own; some individuals can not say when did the tear occur
Crackling sounds when moving the shoulder
Reference: ^[2]

Diagnostic Tests

Isolated supraspinatus tear may or may not decrease the range of motion in the shoulder.

Empty-can test ^[6]. While sitting or standing, reach forward with your both arms at the shoulder level. Move each arm about 30 degrees to the right and left respectively and turn the hands down, like when emptying a can. An examiner applies downward pressure on each of your forearms. If you are unable to resist the pressure it means you may have a supraspinatus tear. By one estimation, the empty-can test reveals supraspinatus tear in 44% cases (44% sensitivity) and is 90% specific (in 10% other causes are involved) ^[4].

Full-can test ^[6]. Have the same position as in the previous test, but with thumbs up. Inability to resist downward pressure speaks for a supraspinatus tear.

Video 1. Supraspinatus tendon rupture assessment
(impingement, empty-can, Neer, Hawkins-Kennedy and drop arm test)

Imaging investigations. An X-ray can show eventual fractures, dislocation or calcification, but not tendon tears. Supraspinatus tear can be detected by arthroscopy, ultrasound scan and magnetic resonance image (MRI) ^[2].

Differential Diagnosis

Other acute conditions that can cause pain in the shoulder:

Contusion
Infraspinatus tear
Bicipital tendonitis
Acromioclavicular joint injury
Brachial plexus injury

Chronic conditions:

Calcifying tendonitis of rotator cuff
Subacromial bursitis
Myofascial pain
Herniated disc in the neck spine
Rheumatoid arthritis in the neck spine
Superior labrum tear, arthritis, adhesive capsulitis (frozen shoulder), shoulder dislocation or other shoulder condition
Thoracic outlet syndrome

Treatment

Nonsurgical treatment includes rest, ice packs (in the first 48 hours after an injury), heat pads, NSAIDs, steroid injections and exercises ^[3]. Friction massage for 4-6 weeks helps to heal the tendon correctly ^[10].

In non-traumatic supraspinatus tears, physiotherapy can be equally effective as surgery ^[13].

After an acute injury with a full thickness supraspinatus tear or when pain persists despite conservative treatment, a doctor can suggest an arthroscopic or surgical reattachment of the muscle ^[2,11]. Rotator cuff tear is not an emergency, but the current recommendation is to have a surgery within a month after an injury ^[4]. Tear that involves up to 30% of the tendon can heal on its own without repair ^[12].

Recovery Period

The recovery period after an arthroscopic tendon repair is usually 3-6 months ^[9]. Full recovery after an open surgery may last up to a year ^[4]. A doctor may instruct you to wear a sling or use the affected arm only at the elbow and lifting nothing heavier than a cup of coffee for 3 months after surgery ^[4].

Stretching Exercises

Stretching exercises are intended to maintain the range of motion in the shoulder. They should be gentle and should not cause pain.

Exercise 1 ^[4]. When lying with the face up, raise an extended arm on the affected side up by the help of the opposite hand holding an elbow.

Exercise 2 ^[7]. Stand parallel to a table and lean slightly forward with the healthy arm leaning onto a table and with the affected arm hanging freely down. Swing with the affected arm forwards and backward, side to side and in a circular manner.

Strengthening Exercises

Strengthening exercises should be done only when the tendon is already healed and the exercises do not cause pain, which is usually about 3 months after the injury ^[4].

Video 2. Strengthening exercises for supraspinatus muscle

References

Supraspinatus Muscle and Tendon Anatomy