A shoulder impingement occurs when soft tissues are “pinched” between the underside of the AC joint and the top of your humerus. For those of you who are unfamiliar with these structures, the AC joint is made up of the outer portion of your collar bone and a hook of bone that comes off the top of your shoulder blade.
Shoulder injuries involving a rotator cuff tear are common in my San Diego chiropractic office, this is because these muscles are small and easily strained (strain means that some fibers have torn). Sports injuries work injuries and auto accidents commonly cause strains in the rotator cuff muscles.
The muscles of the rotator cuff coordinate rotational movements of the shoulder. There are four rotator cuff muscles as follows: supraspinatus, infraspinatus, teres minor and the subscapularis. The supraspinatus works to lift your arm off the site of your body and it is the most frequently injured of the rotator cuff muscles. The infraspinatus and teres minor both externally rotate your shoulder. Finally, the subscapularis works to internally rotate your shoulder.
Although the supraspinatus is the most frequently injured rotator cuffmuscle, a strain of any of these muscles can cause shoulder pain and significant range of motion loss in the affected shoulder.