Rotator Cuff

The shoulder joint consists of 3 bones – the upper arm (the humerus) the shoulder blade (the scapula) and the collarbone (the clavicle). The humerus and scapula form a “ball and socket” joint. The scapula has a very shallow socket called the glenoid, and the humerus has a very large ball on the end that fits into this shallow socket. This makes the shoulder joint (the glenohumeral joint) the most mobile joint in the body, but also the most unstable one. Therefore, the shoulder relies heavily on three different layers of soft tissue to hold it together.

  1. The innermost layer of tissue holding the shoulder together is the labrum. The labrum acts as sort of a “gasket” attached around the rim of the socket. It increases the contact area between the ball and socket to improve stability.
  2. Moving outward from the inside of the joint, the next stabilizing tissue in the shoulder is the joint capsule. The capsule is made up of ligamentous tissue that holds the ball and socket together. To do its job effectively, the capsule must be tight enough to keep the joint together, but loose enough to allow for full range of motion. It is actually the capsule that determines how far the shoulder joint is able to move.
  1. The outermost layer of tissue that helps stabilize the shoulder is the rotator cuff, which is made up of four muscles. The rotator cuff tendons lie on top of the joint capsule and give contractile capability to help stabilize the joint. The subscapularis muscle runs across the front of the joint capsule and helps to rotate the shoulder in towards the body. The infraspinatus and teres minor run across the back of the joint and help to rotate the shoulder out. The supraspinatus lies on top, and does not rotate the shoulder as much as it controls the shoulder mechanics with elevation of the arm. Your deltoid muscle is the major muscle that elevates your shoulder (lifts it up or out). Because of the way the deltoid attaches, if it were to work alone, it would simply pull the humeral head up. Due to the supraspinatus’ attachment on the humerus, when the arm is elevated, the supraspinatus pulls the humeral head into the joint and keeps the humeral head from rising up in the joint. The other three cuff muscles help pull the humeral head down.

Injuries to the Rotator Cuff

There are a few injuries to the rotator cuff that can significantly impact the function of the shoulder.

  1. With primary shoulder impingement, the cuff, especially the supraspinatus, is not controlling the mechanics of the shoulder as it should. As you elevate your arm, the humeral head rides up, pinching the soft tissue structures that lay between it and the roof over your shoulder that is created by a part of your shoulder blade called the acromion. The main tendon affected is the supraspinatus. You also have a fluid filled sac called the subacromial bursa that can get pinched and become painful as well. Impingement syndrome can be very painful and will affect one’s ability to elevate the arm without pain. This is called bursitis. Unfortunately, the rotator cuff muscles are small and do not have great endurance. If you do an overhead activity like swimming, or pitching over and over, the muscles gets tired. The more fatigued they become, the more trouble they have controlling the mechanics of the shoulder. Now the rotator cuff tendons begin to get pinched between the bones. As they get pinched, they get irritated. As they get irritated, the muscles lose strength. Since their job is to prevent the bones from getting pinched in the first place, you can see the problem. You are injuring the muscles that need to act as a safety device. That is easy, you say. If it hurts, I will stop. Unfortunately, it is not that simple. When tendons begin to get irritated, you usually don’t know it. There is enough blood flowing to the area warm and prevent significant swelling, so you keep going. When you hit the danger spot of either too much swelling or too much damage to the tendons, it is too late. Now even rest may not be enough.
  1. Secondary shoulder impingement is the compression of the rotator cuff tendons between the humerus and the back (posterior) aspect of the glenoid socket. In the case of a secondary impingement, the shoulder joint is often loose or unstable. The ligaments of this joint do not do an efficient job at holding the humerus in the socket. Consequently, in certain positions, the head of the humerus can migrate forward (anteriorly) and cause a trapping phenomenon of the rotator cuff tendons in the back of the shoulder joint. This type of impingement is seen more often in a population of individuals who have loose joints or what is often clinically referred to as joint instability. It is most commonly seen in throwers.You can also injure your rotator cuff with a fall or hit to the shoulder drives the bones together. The force traps the rotator cuff tendons and injures them. The rotator cuff can no longer function to control joint mechanics, and the injury gets worse. This describes a traumatic rotator cuff “tendonitis”.
  1. A rotator cuff tear occurs when there is enough force or enough stress of a long period of time to significantly tear the muscle or tendon apart. Because tendons retract like an elastic when they are torn, they cannot repair themselves. Rotator cuff tears are more serious and surgery may be required to repair the tear.
  1. Another cause of rotator cuff injuries is a muscle imbalance. We tend to have strong front muscles and less developed back muscles. The front muscles get stronger with sports, jobs, and household chores because almost everything we do is in the front of us. We also tend to work these large muscle groups out more in the gym because they are the muscles we see. Meanwhile, we ignore our rotator cuff. No wonder these muscles get tired so easily. This imbalance may also add to our frequency of neck and upper back stains, or other shoulder injuries.

Prevention of Rotator Cuff Injuries

  • Avoid excessive overhead activities.
  • If you have increased work at home using the shoulder (i.e. painting, yard work, lifting, scrubbing the floor, etc.)
  • Try to spread the work out over a few days.
  • Avoid excessive reaching (use ladders or other ways to get as close as possible to your work).
  • If you are beginning a shoulder sport like golf, aerobics, swimming, etc.
  • Stay safe in the offseason.
  • Increase rest in between activities (avoid consecutive days).
  • Alternate underhand with overhead activities (do more sidestroke in swimming, cut down on overhead serves).
  • Start out very conservatively with the amount of weight, amount of repetitions, or durations.
  • If you are beginning a weight program:
  • Start with minimal overhead lifting.
  • Start at a conservative weight.
  • Wait 1-2 week before you try a more “stressful weight”.
  • Obtain exercise advice from a knowledgeable source – you want to work the muscles in the back of the shoulder.
  • Include rotator cuff strengthening exercises.
  • If you think of starting aerobics with arm weights (or running with “heavy hands”)
  • Make sure you are completely without weights for at least one month.
  • Start out with minimal weight for a small amount of time on alternative workouts.
  • Obtain a good warm-up and stretching program to do before shoulder activity.


  1. REST!
  2. Ice (a large food storage bag filled with ice and water will drape over shoulders) for 10 – 15 minutes, 2 or more times per day.
  3. Keep arm flexible by doing stretching exercises.
  4. If pain persists, or if you are losing motion, seek professional help.