Supraspinatus Tendinitis

Supraspinatus Tendinopathy

Supraspinatus tendinopathy is a common and disabling condition that becomes more prevalent after middle age and is a common cause of pain in the shoulder. A predisposing factor is resistive overuse.

The supraspinatus tendon of the rotator cuff is involved and affected tendons of the musculoskeletal system and becomes degenerated, most often as a result of repetitive stresses and overloading during sports or occupational activities.The tendon of the supraspinatus commonly impinges under the acromion as it passes between the acromion and the humeral head. This mechanism is multifactorial .

Anatomy Of Supraspinatus Muscle

The supraspinatus muscle is of the greatest practical importance in the rotator cuff, derives its innervation from the suprascapular nerve and stabilises the schoulder, exorotates and helps abduct (lift up sideways) the arm, by initiating the abduction of the humerus on the scapula.
Any friction between the tendon and the acromion is normally reduced by the sub-acromial bursa.

The anterior margin of the supraspinatus is defined by the posterior edge of the rotator interval that separates the supraspinatus from the rolled superior border of the subscapularis. The posterior margin of the supraspinatus is marked by the extension of the raphe between supraspinatus and infraspinatus around the scapular spine. The anterior portion of the supraspinatus is composed of a long and thick tendinous component whereas the posterior portion has been shown to be short and thin.

An anatomic dissection study of the supraspinatus footprint found that the mean anterior to posterior dimension of the supraspinatus tendon was 25 mm, with a mean medial to lateral thickness of the footprint of 12 mm – the mean distance from the cartilage to the supraspinatus footprint was 1.5 mm at mid tendon.


Anatomy Of Supraspinatus Muscle

The supraspinatus and infraspinatus tendons fuse 1.5 cm proximal to their insertions. Collagen is the major matrix protein of supraspinatus tendons, consisting of > 95% type I collagen, with lesser amounts of other collagens including collagen type III.

The anatomy of the supraspinatus’s insertion is of key relevance in terms of its extracellular matrix composition and has been categorised into four transition zones[16]. The first zone is proper tendon, made up of largely type I collagen and small amounts of decorin. The second zone is fibrocartilage and consists of largely types II and III collagen, with small amounts of types I, IX and X collagen. The third zone is mineralised fibrocartilage and consists of type II collagen, with significant amounts of type X collagen and aggrecan. The fourth zone is bone and is largely type I collagen with a high mineral content. This effective bone-tendon attachment is achieved through a functional grading in mineral content and collagen fibre orientation. The supraspinatus enthesis is a highly specialised in homogeneous structure that is subjected to both tensile and compressive forces.

Which are Sign/Symptoms Of Supraspinatus Tendinitis?

Patients present with progressive subdeltoid aching that is aggravated by abduction, elevation, or sustained overhead activity. They feel also tenderness and a burning sensation in their shoulder. The pain may radiate to the lateral upper arm or may be located in the top and front of the shoulder. It typically becomes worse with overhead activity. Initially, the pain is felt during activities only, but eventually may occur at rest.

One has to think of supraspinatus tendinopathy when the patient says:

  • Pain increases with reaching.
  • Pain is felt after frequent repetitive activity at, or above shoulder.
  • Patient feels weakness of resisted abduction and forward flexion, especially with pushing and overhead movements.
  • Patient has difficulty sleeping at night due to pain, especially when lying on the affected shoulder, and with an inability to sleep.
  • Patient has difficulties with simple movements, such as brushing hair, putting on a shirt or jacket, or reaching the arm above shoulder height.
  • Patient has a limited range of motion in the shoulder.
  • Patient had a former shoulder trauma.
  • The shoulder may be warm and there may be fullness anterolaterally. Further, there is a painful arc between 70° and 120° of abduction.

So supraspinatus tendinitis is usually consistent with anterior instability causing posterior tightness. The problems that patient with Supraspinatus Tendinitis complain off, are pain, inflammation, decreased ROM, strength, and functional activity.

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