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What is the rotator cuff?

Rotator Cuff

A rotator cuff is a group of four muscles – supraspinatus, infraspinatus, teres minor, and subscapularis - that come together as tendons around the head of the humerus, the large bone that makes up the upper arm. The rotator cuff is separated from the top shoulder bone, the acromion, by a fluid-filled sac called a bursa, which acts as a lubricant by reducing friction. The rotator cuff functions to keep the arm attached to the shoulder socket and allows for the arm to be lifted and rotated.

What are the different rotator cuff pathologies?

Rotator cuff tendinitis/tendinosis: injuries to the rotator cuff that result from chronic overuse or acute injuries, leading to partial- or full-thickness rotator cuff tears.

Shoulder impingement: results from the acromion rubbing against the rotator cuff, causing pain and irritation. Shoulder impingement is commonly found in athletes that are required to perform overhead throwing motions. Internal impingement results from the impingement of the rotator cuff by the posterior outer rim of the shoulder socket, called the glenoid when the arm is maximally away from the torso or rotated outwards during a throw. External shoulder impingement results from impingement of the rotator cuff by the acromion, also resulting in inflammation of the bursa or bursitis.

Symptoms of a rotator cuff injury include the onset of pain without any preceding injuries to the affected area, increasing pain with overhead throwing motions, and experiencing pain at night.

How are rotator cuff pathologies diagnosed?

Physicians will examine the shoulder for symmetry, posture, muscle mass, and whether the shoulder blade is protruding (scapular winging). Active – when the patient moves the shoulder joint on their own- and passive- when the physician moves the patient’s shoulder - ranges of motion of the shoulder will then be assessed. Patients with a rotator cuff pathology will generally exhibit a limited active range of motion but a full passive range of motion. Several tests are used to assess for rotator cuff pathology:

The supraspinatus muscle of the rotator cuff:

Jobe’s test: the arm is held at a 90° angle from the torso, in front of the patient, while the physician rotates the arm inwards. The hand should be open with the thumb pointing downwards. Pain or weakness is indicative of a positive test.

Drop arm test: the physician holds the patient’s affected arm at a 90°-degree angle to their side while supporting the patient at the elbow. The arm is then rotated outwards and the physician stops supporting the arm. A positive sign occurs when the patient is unable to maintain their arm at the initial position.

The infraspinatus muscle of the rotator cuff:

Strength testing: the arm is held against the side of the trunk with the elbow bent at 90°, and the patient rotates the arm outwards, resisted by the physician.

External rotation lag sign: the patient holds the arm at their side with the elbow bent at 90°. The examiner then holds onto the patient’s wrist and maximally rotates the arm outwards. Once the examiner lets go of the patient’s arm, if the shoulder begins to rotate inwards, the test is considered positive.

The teres minor muscle of the rotator cuff:

Strength test: the arm is held at a 90° angle away from the body, with the elbow also bent at 90°. The examiner then rotates the arm externally, and the patient is told to resist the motion.

Hornblower’s sign: the patient holds their arm at the same position as in the strength test and the examiner maximally rotates the arm externally. If the arm begins to rotate internally and the patient is unable to maintain the same position once the examiner lets go, this is considered a positive test.


IR lag sign: the arm is brought behind the patient’s torso, with the elbow bent at 90°. The examiner then lifts the back of the patient’s arm away from their back and supports the wrist and elbow. The test is considered positive if the patient is unable to maintain the same position without the examiner’s support.

Passive external rotation range of motion: if the shoulder has greater assisted external rotation in comparison to the other shoulder, this is indicative of a partial or complete muscle tear.

Lift off test: the arm is placed in the same position as in the IR lag sign test. The examiner then presses the back of the patient’s hand into their lower back while the patient is told to lift the hand away.

Belly press: the patient bends their elbow by 90° and places the palm of their hand onto their stomach. The elbow is supported by the examiner, and the test is considered positive if the patient is unable to maintain this position once the examiner lets go.

Subacromial/external impingement:

Neer impingement sign: the sign is considered positive if the patient feels pain when an examiner bends their arm at the elbow greater than 90°.

Neer impingement test: the test is positive if the patient reports less pain when performing the Neer impingement test after a subacromial injection.

Hawkin’s test: the examiner positions the arm in front of the patient, with the elbow bent at 90°. A positive test occurs if the patient feels pain when the examiner rotates the shoulder inwards.

Internal impingement:

Internal impingement test: the patient is instructed to lay on their back and the examiner brings the arm to a 90° angle from the torso, with the elbow also bent at 90°. The examiner then rotates the arm outwards. The test is positive if the patient experiences pain with rotation.

Other diagnostic evaluations:

Radiographic imaging of the glenohumeral, or shoulder, joint, ultrasounds, and MRI scans can be used to identify and diagnose rotator cuff pathology


Different treatments will be used depending on the severity of the rotator cuff tear.

Group 1 tears include asymptomatic partial-thickness or full-thickness rotator cuff tears. Nonoperative treatment is recommended.

Group 2 tears include symptomatic partial-thickness tears. These tears are first managed nonoperatively and surgical intervention is recommended anywhere from 3 to 18 months of nonoperative treatment. Whether or not a patient will require surgical intervention depends on the individual and their improvement with nonoperative treatment.

Group 3 tears include symptomatic, chronic rotator cuff tears. Again, the decision to proceed with surgical treatment varies depending on the individual.

Nonoperative treatment includes physical therapy which includes rotator cuff and periscapular strengthening and range of motion exercises. Anti-inflammatory medications such as NSAIDs may also be used. Other treatment modalities include iontophoresis and transcutaneous electrical nerve stimulations, both involving an electric current being sent to the affected area, cortisone injections, and rest from any activities that worsen symptoms.

Surgical treatments include the following:

  • Subacromial decompression: an arthroscopic (a small camera inserted into the shoulder joint is used to display pictures on a larger screen) procedure that involves the debridement of the underside of the highest part of the shoulder blade, the acromion. Subacromial decompression may also include cutting a ligament that connects the acromion to another part of the shoulder blade called the coracoid process, also known as the coracoacromial arch, and removal of the subacromial bursa. This allows for the rotator cuff to move much more freely and prevents it from swelling and rubbing against the acromion. This surgery is commonly used to treat impingement if conservative treatment fails.
  • Rotator cuff repair: for full-thickness rotator cuff tears, a repair involves re-attaching or stitching the torn tendon to the humerus. For partial-thickness tear, the affected area will be debrided. A rotator cuff repair is recommended if conservative treatment fails to relieve symptoms, the tear is larger than 3 cm and surrounding tissue quality is good, the affected area greatly impairs shoulder function, and if the tear was caused by recent and acute trauma. A rotator cuff repair may be done as an open repair, often requiring several centimeter-long incisions, an arthroscopic repair, or a mini-open repair where the incision is 3 to 5 cm long and an arthroscope is used to assess the damage done to structures within the joint followed by repair by viewing the structures directly.


For subacromial decompression, the patients wear a sling for 1 to 2 weeks and are advised to avoid heavy lifting and exercises. They may participate in passive range of motion rehabilitation as well as utilize cryotherapy for the first 10 to 14 days after the surgery. Once they discontinue wearing the sling, they can begin physical therapy and active range of motion exercises by 3 to 6 weeks postoperatively. They can resume sports in 6 to 8 weeks. For a rotator cuff repair, patients will also be kept in a sling, most likely for the first 4 to 6 weeks depending on the severity of the injury. Once the physician determines that it is safe for the patient to move the shoulder, the physical therapist will help the patient perform a passive range of motion exercises within 4 to 6 weeks after surgery. Patients begin more active range of motion exercises after 6-8weeks and begin strength training at 8 to 12 weeks. Complete recovery is expected after six months.


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