Impingement in the shoulder is a common occurrence and accounts for the largest percentage of all shoulder pain. Impingement refers to the pinching effect which can occur between the humerus and the acromion. The structures which can get caught between the acromion and humerus are the rotator cuff tendons, the biceps tendon and the subacromial bursa.
The symptoms include pain especially with overhead activities and in an arc when raising the arm to the front or to the side. This pain can get to be quite sharp and will limit the amount of shoulder movement available.
Often impingement syndromes can be triggered by repeated overhead activities such as work activities or sports such as swimming, tennis and those which involve a lot of throwing. These injuries are often referred to as swimmer’s or thrower’s shoulder, whichever is appropriate.
It is an inflammatory process in which the swelling in the tendons or bursa further reduces the space between the humerus and acromion leading to further impingement. If the bursa is involved it will be tender and may be spongy to feel. This is known as subacromial bursitis.
If the tendons are involved they become inflamed and irritated due to the repeated impingement between the bones. As the tissues become worn, there is a decreased stabilising effect on the joint. As a response to this the deltoid muscle increases its activity which in fact increases the impingement force. Chronic impingement can lead to tears in the tendons.
Factors which influence the development and progression of impingement include the shape of the acromion, which is especially significant if the acromion is in a hook shape, as well as the blood supply to the tendon which is poor in the most commonly impinged areas. Probably the most important factor is the biomechanics of the shoulder, specifically the dynamic stability of the shoulder blade. If the shoulder blade is not stable, attempting to move the arm will pull the shoulder blade out of position increasing the likelihood of the acromion pushing against the humerus.
Your physiotherapist may work on stretching around the shoulder, restoring full mobility, decreasing inflammation and pain, restoring correct biomechanics and restoring correct movement patterns.