Why do most rotator cuff injuries involve the suprasipatus muscle?

Anatomy: The supraspinatus muscle in vulnerable to tearing due to its anatomic position and the biomechanics of the shoulder complex. The tendon of the supraspinatus muscle passes under the acromion of the acriomioclavicular joint. Arthritis and inflammation in this area can lead to injury of supraspinatus tendon.

Blood supply: The supraspinatus tendon receives its blood supply from both the humerus and from the muscle, which is very vascular. Midway between the tendon and bone is a watershed area with a relative lack of blood supply, often called the critical zone. It is this area, between 10-15mm posterior to the biceps tendon, that most degenerative tears of the supraspinatus occur.

More on Rotator Cuff: We also see subscapularis tears in approximately 35% of the rotator cuff tears we treat. Learn more here: http://theshouldercenter.Com/rotator-cuff-tear.Htm and http://www.Theshouldercenter.Com/shoulderpain/2013/rotator-cuff-repair-2/rotator-cuff-tear-subscapularis/.