Why your shoulder hurts...
Part 1: The Explanation.
This is not medical advice. Consult your doctor and/or physical therapist before attempting any of the exercises in this article.
Most of us take lifting our arm overhead for granted. However the design of the shoulder makes it inherently unstable. The shoulder is a very poor 3rd class lever.
The action of pull by the deltoid (red outline) is only 6” on a 25-30" lever arm. The blue lines are the lines of pull of the rotator cuff muscles. They pull the ball down and retracted, and into the socket. The rotator cuff muscles are an anchor system or counter weight against the weight of an outstretched arm. Notice how small the socket is in relation to the ball, and not very deep. The yellow lightning bolt is impingement. This is where the mechanics of the shoulder matter most. As the rotator cuff fails to hold the ball down in the socket so it can rotate overhead, the ball pinches the supraspinatus muscle under the acromion process. This causes pain and further hiking of the shoulder, instead of rotation.
This position of the arm is what is tested in the industry, yet this is not a functional movement. We do not walk around like robots. We efficiently bend the elbow to shorten the lever arm and decrease torque on the shoulder.
A good analogy is to think of your arm as a fishing pole. If you caught a heavy fish, you would grab the pole high up for leverage. Your shoulder can’t do this, and the deltoid must pull from the bottom only. This severe strain often causes injury. Shoulder injuries can account for 20-30% of a clinic’s customers. The biggest reason for that, is because the shoulder is designed for mobility, not stability.
A healthy shoulder has 360 degrees of motion in the sagittal plane, about 200 in the transverse and 210 in the frontal plane. The ball and socket configuration is really only held together by soft tissues; rotator cuff muscles, some ligaments and tendons, a labrum and capsule. As shown above, the socket is not very big or deep, which allows for even more loose play.
Part of the reason you hear so much about the rotator cuff muscles is because they are much smaller than the other prime movers. This makes them more prone to injury. We also tend to perform less manual labor as a population, and do not use many pulling muscles, such as raking or rope pulling. Pulling motions work more of the rotator cuff. The ball and socket will be unbalanced if there is more overhead activity versus pulling motions.
Shoulders will be tested and diagnosed with various problems including rotator cuff tears, labrum tears, bursitis, impingement, etc. The common theme among shoulders is leverage, mechanics and weakness as the root cause of injury. Ultimately we are injured when our muscles are not strong enough to overcome the forces in our environment. Add very poor leverage and extreme range of motion, and it’s easier to see why the shoulder is a common injury.
Most shoulders injuries involve some type of loss of range of motion. The first goal should always be to restore that range of motion if possible. A shoulder has a much better chance of being pain free and functional if full range of motion is restored. This is partially due to the mechanics between the scapula and humerus. As people strain against pain and limitations to lift their shoulder, the body will often “cheat” with shoulder shrugging. This is not the same as the original pain free rotation seen in a healthy shoulder.
This link below is for part 2, the exercises,
