Shoulder impingement syndrome is a condition where your shoulders rotator cuff tendons and bursa are intermittently trapped and compressed during shoulder movements. This causes injury to the shoulder tendons and bursa resulting in painful shoulder movements. Impingement (impact on bone into rotator cuff tendon or bursa) should not occur during normal shoulder function. When it does happen, the rotator cuff tendon becomes inflamed and swollen, a condition called rotator cuff tendonitis. Likewise if the bursa becomes inflamed, shoulder bursitis will develop. Both these conditions can co-exist or be present independently. While a traumatic injury such as a fall can cause it, it is repeated movement of your arm into the impingement zone overhead that most frequently causes the rotator cuff to contact the outer end of the shoulder blade (acromion). When this repeatedly occurs, the swollen rotator cuff is trapped and pinched under the acromion. Injuries vary from mild tendon inflammation (tendonitis), bursitis (inflamed bursa), calcific tendonitis (bone forming within the tendon) through to partial and full thickness rotator cuff tendon tears, which may require surgery. The shoulders rotator cuff tendons are protected from simple knocks and bumps by bones (mainly the acromion) and ligaments that form a protective arch over the top of your shoulder. In between the rotator cuff tendons and the bony arch is the subacromial bursa (a lubricating sack), which helps to protect the tendons from touching the bone and provide a smooth surface for the tendons to glide over. However, nothing is fool proof. Any of these structures can be injured, whether they be your bones, muscles, tendons, ligaments or bursas. Shoulder impingement has primary (structural) and secondary (posture & movement related) causes. Primary Rotator Cuff Impingement is a structural narrowing that some of us are born with causing a smaller sub-acromial space. Conditions such as osteoarthritis can also cause the growth of subacromial 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 subacromial space, which results in bursitis or shoulder tendonitis. Secondary Rotator Cuff Impingement is resultant from “dynamic instability” of the shoulder. Impingement can occur if you have a dynamically unstable shoulder. This means that there is 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 weakened due to pain inhibition or tendon tears. When your rotator cuff fails to work normally, it is unable to 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 tendonitis.

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