The shoulder joint is made up of the humerus (arm bone), clavicle (collarbone) and scapula (shoulder blade). The head of the humerus fits into the glenoid cavity of the scapula to form a ball-and-socket joint. The arm is then firmly kept together within this shallow socket by the rotator cuff, which is a complex group of muscles and tendons that team up to form a covering around the head of the humerus. The rotator cuff muscles which arise from the scapula and attach to the humeral head, provides strength and stability during shoulder motion.

Rotator Cuff Front View
Rotator Cuff Back View

The rotator cuff muscles, also known as the ‘SITS’ muscles are made up of the supraspinatus, infraspinatus, teres minor and subscapularis, respectively. The table shows the primary function of each rotator cuff muscle.

MusclePrimary Function
SupraspinatusAbduction of arm (first 15° only)
InfraspinatusExternal rotation of arm
Teres minorExternal rotation of arm
SubscapularisInternal rotation of arm

Between the rotator cuff and the acromion process of the scapula, is a lubricating, fluid-filled sac known as a bursa. The bursa covers and protects the muscles and tendons, keeping them from close contact with surrounding bones, thereby allowing the tendons to glide freely during arm movement. Thus, when the rotator cuff tendons become injured or damaged, this bursa may also become inflamed and painful.

Rotator Cuff Strain

Rotator cuff injuries are the most common cause of shoulder pain and disability among adults. This injury is common in patients over the age of 40, but can affect those who are younger too. They are also usually more common in males than in females. A rotator cuff strain is the over stretching or tearing of the rotator cuff tendon or muscle belly. The severity of the muscle strain depends on how much fibres were damaged, intensity of pain and the strength of muscle contraction.

Causes of Rotator Cuff Strain

There are two main causes of rotator cuff strain: acute traumatic and degenerative. Acute traumatic strains usually occur after a specific trauma such as, falling on an outstretched hand (FOOSH), or a single violent force or blow to the shoulder. Besides, prolonged or repetitive overuse of the rotator cuff over a short period of time – especially in athletes who repeatedly make overhead or forceful pulling motions are more prone to rotator cuff strain. Acute traumatic strains can also occur when overexerting during lifting or pulling something that is too heavy, or if a pre-existing shoulder impingement syndrome is already present.

Degenerative strains are as a result of the wear and tear of the rotator cuff tendon that occurs slowly over time, and it is usually painless. This type of strain is more common in the dominant arm, but if a degenerative strain is present in one arm, there is a higher likelihood of a rotator cuff strain in the opposite arm too, even if no pain is felt. It is usually associated with minimal trauma secondary to long-standing tendonitis or chronic impingement syndrome.


  • Pain at the top and side of the shoulder.
  • ‘Popping’ or tearing sound at the point of injury, followed by pain and weakness of the shoulder.
  • Pain is worsened when leaning on elbow and shrugging the shoulder upwards.
  • Unable to tolerate overhead motion.
  • Pain that is present even at night, especially when weight-bearing on the affected shoulder.
  • Gradual loss of range-of-motion on the affected shoulder if the injury has been persisting for a while, without treatment.
  • Loss of strength in the shoulder.
  • ‘Clicking’ or ‘snapping’ sounds (crepitus) during shoulder motion.
  • Redness and swelling in the affected shoulder (in more severe cases).

Assessment of Rotator Cuff

A chiropractor would first take a detailed history to gain a better understanding of your condition. Next, a series of tests would be done during the physical examination to confirm the diagnosis, or rule it out. If the history and physical examination point towards a rotator cuff strain, it is also during this time that which of the four rotator cuff muscles are affected and the severity of injury has to be determined – it may be one or more rotator cuff muscle and findings may indicate a over stretch or a tear (partial or complete), respectively. Should there be any need for further investigation, referral for an MRI, X-ray or ultrasound imaging of the shoulder may be warranted.

Management of Rotator Cuff

For a stretched or partially torn muscle, conservative care can help improve pain, function and reduce disability. Modalities such as, therapeutic ultrasound, laser and interferential current therapies aid in reducing pain and swelling. Chiropractors also employ spinal manipulation of the neck and upper back to help ease the tension around the shoulder. These can take from 2 weeks up to 3 months to recover, and even more so depending on severity which can take up to a year of treatment to recover. For a completely torn muscle, surgical consult may be warranted instead.

陳政汶脊骨神經科醫生 (Dr. Tan Ching Boon) 。專業資格:香港註冊脊醫、英國英歐脊科醫學院脊骨神經科碩士。專注範圍包括姿勢矯正、頭痛、背痛、與椎間盤突出症、肌肉拉傷、關節扭傷有關的頸椎和腰椎神經根病症。網上搜尋陳政汶脊醫診所電話