Rotator Cuff Impingement
Rotator cuff impingement and bursitis causes have primary (structural) and secondary (posture & movement related) causes.
Primary Rotator Cuff Impingement – Structural Narrowing
Some of us are born with a smaller sub-acromial space. Conditions such as osteoarthritis can also cause the growth of sub-acromial bony spurs, which further narrows the space.
Because of this structural narrowing, you are more likely to squash, impinge and irritate the soft tissues in the sub-acromial space, which results in bursitis or rotator cuff tendonitis.
Secondary Rotator Cuff Impingement – Dynamic Instability
Impingement can occur if you have a dynamically unstable shoulder.
This means a combination of excessive joint movement, ligament laxity and muscular weakness around the shoulder joint.
This impingement usually occurs over time due to repetitive overhead activity, trauma, previous injury, poor posture or inactivity.
In an unstable shoulder, the rotator cuff has to work harder, which can cause injury.
An overworking rotator cuff fatigues and eventually becomes inflamed and weakens due to pain inhibition or tendon tears.
When your rotator cuff fails to work normally, it cannot prevent the head of the humerus (upper arm) from riding up into the sub-acromial space, causing the bursa or tendons to be squashed.
Failure to properly treat this instability causes the injury to recur. Poor technique or bad training habits such as training too hard is also a common cause of overuse injuries, such as bursitis or tendinopathy.