By nature the shoulder is one of the most unstable joints in the body. The head of humerus, (arm bone), is 3-4x larger than the joint it attaches to. Many compare this to a gold ball sitting on a tee or a seal trying to balance a ball on their nose. Because of this the joint is more suspectable to trauma and injury.
One of the most common injuries seen in the shoulder that causes pain is shoulder impingement. The cause of which is progressive pressure on the tendons of the rotator cuff from bone or soft tissue. Right above the shoulder is a delicate space known as the subacromial space. This small area houses the supraspinatus tendon and the subacromial bursa; (a bursa is a fluid filled sac that is meant to reduce friction when two objects are sliding against one another).
If shoulder mechanics are improper we can see a superior translation of the humerus into this subacromial space. Over time, the small wear and tear created by pressure of the bone hitting the bursa or tendon causes pain.
Common signs associated with impingement syndrome include:
·Increased mobility of the anterior capsule
·Decreased mobility of the posterior capsule
·Excessive external rotation with limited internal rotation
·Painful arc of motion (pinching when lifting arm overhead between 60 and 120 degrees)
The most common cause of impingement syndrome is elevation and internal rotation because a part of the bone (greater tuberosity) has no choice but to hit the subacromial space when in internal rotation. This is commonly seen in: baseball players, golfers, tennis players, swimmer's, and CrossFit athletes.
During proper elevation of the arm external rotation accompanies elevation to move the greater tuberosity out of the way. If the muscles of the rotator cuff are out of position, inhibited, or weakened they can not create sufficient external rotation while the arm if being lifted. The muscles of the rotator cuff create compression and also have to be able to rotate the arm, especially the infraspinatus.
If there is not good activation of the rotator cuff then the strong pull of the deltoid moves the arm superiorly into the subacromial space causing irritation to the supraspinatus and subacromial bursa. To combat this we need good synergistic activity of the rotator cuff along with proper positioning of the scapula to maximize muscular pull.