The impingement implies an extrinsic compression of the rotator cuff tendons in the subacromial space. This compression can happen due to the size and the shape of the acromion (according to Bigliani et al, there are three variations of the acromion), due to the thickening of the coracoacromial ligament, due to the formation of osteophytes in the undersurface of the acromioclavicular joint, or even due to the thickening or hypertrophy of the subacromial bursa and rotator cuff tendons.
The causes for shoulder impingement can be primary or secondary. The primary causes include increased subacromial loading, acromial morphology, acromioclavicular arthrosis, coracoacromial ligament hypertrophy, coracoid impingement, subacromial bursal thickening and fibrosis, prominent humeral greater tuberosity, trauma or overhead activity. The secondary causes include rotator cuff overload/soft tissue imbalance, eccentric muscle overload, glenohumeral laxity/instability, long head of the biceps tendon laxity/weakness, glenoid labral lesions, muscle imbalance, scapular dyskinesia, posterior capsule tightness, trapezius paralysis (Chang, W.K., 2004).
In patients younger than 40 years of age history may include usually glenohumeral instability and/or acromioclavicular joint disease/injury. In patients alder than 40 years of age history may include glenohumeral impingement syndrome/rotator cuff disease and/or glenohumeral joint degenerative joint disease.Regarding to athletic activity, it should be considered the onset of symptoms in relation to specific phases of the athletic event performed, the duration and frequency of play, the duration and frequency of practice, the level of play (little league, pre-high school, high school, college, professional), the actual playing time (starter, backup, bench player), and the position played. The chronicity and location of the symptoms should be considered. Gradual increase in shoulder pain with overhead activities suggests an impingement problem (a sudden onset of sharp pain in the shoulder with tearing sensation suggests a rotator cuff tear, shoulder pain usually lateral, superior or anterior refers to the deltoid region, pain with humerus in forward flexed and internally rotated position suggests rotator cuff impingement, pain with humerus in abducted and externally rotated position suggests anterior glenohumeral instability and laxity). The quality of pain (sharp, dull, radiation, throbbing, burning, constant, intermittent, occasional), the quantity of pain (scale 1 to 10), alleviating and aggravating factors, associated manifestations (stiffness, numbness, paresthesias, clicking, catching, weakness, crepitus, symptoms of instability, neck symptoms), provocative positions (Chang, W.K., 2004).
A thorough palpation of the tendons and muscles of the shoulder joint and scapula should be performed. The supraspinatus muscle and tendon are always affected and inflamed. The biceps tendon, the deltoid muscle, the rotator cuff muscles may also be implied.
There are two tests to assess the impingement: the Neer test and the Hawkins-Kennedy test. In the first, the patient is asked to rotate the shoulder internally. Then, the physical therapist forcefully elevates the shoulder in the scapular plane. This will cause the supraspinatus tendon to be impinged against the anterior inferior acromion (Neer, C.S.). In the second, the patient is asked to flex the arm 90 degrees. Then, the physical therapist forcefully rotates the shoulder internally. This will cause the supraspinatus tendon to be impinged against the coracoacromial ligamentous arch (Hawkins, R.J. and Abrams, J.S., 1992)
Drop arm test
The physical therapist places the patient’s arm in maximum elevation in the scapular plane. The patient is asked to lower it slowly. Sudden dropping of the arm suggests rotator cuff tear (Moseley, H.F., 1960).
Supraspinatus isolation test or empty can test
The supraspinatus can be isolated by asking the patient to rotate the shoulder internally with the arm in 30 degree of flexion and 90 degrees of abduction, so that the thumb is pointing down to the floor. Physical therapist then applies resistance. The test is positive when pain is felt. Weakness may also be present due to the muscle inhibition from the pain stimulus.
For a successful rehabilitation treatment, the patient should eliminate all activities that provokes and exacerbates the symptoms. Physical therapy should begin as quickly as possible. The main goal of the physical therapy is restore the full ROM of the shoulder without any pain, through accessory and passive movements of the glenohumeral joint, acromioclavicular joint, sternoclavicular joint and scapulohumeral joint, and stretching exercises. A deep tissue massage of all muscles and tendons should also be performed, for they may be responsible for low ROM: long portion of the biceps tendon, deltoid muscle, supraspinatus muscle and tendon, rotator cuff muscles and superior trapezius.
Strengthening exercises should be, in an initial phase, isometric, working on the biceps, the triceps, the deltoid (anterior, middle and posterior portions), the external and internal rotator muscles and on the scapular stabilizers (rhomboids, trapezius, serratus anterior, latissimus dorsi and pectoralis major).
The final goal of the rehabilitation treatment is to get the patient or athlete back to their professional activities. In case of non-athletes, exercises that simulate activities of daily living should be done. In case of athletes, this phase includes eccentric exercises. Plyometrics, sports-specifics exercises, proprioceptive neuromuscular facilitation and isokinetic exercices can be initiated. The physical therapist has also an important role in teaching the patient, athlete or non-athlete, what movements should or should be done, and modifications of the technical gesture that may re-exacerbate the symptoms, and warning signs of early impingement.