PT Perspective

with Jason Lau, Doctor of Physical Therapy


The upper part of my right arm gets achy. It doesn’t usually bother me except when I do certain movements like reaching. 


This presentation of symptoms is generally associated with the Rotator Cuff of the shoulder. Non-traumatic problems in the shoulder most commonly involve the Rotator Cuff. 

When discussing the shoulder, I think of the Rotator Cuff muscles as the “weak link”. 

First let’s go over some anatomy basics of the Rotator Cuff. The Rotator Cuff is a set of four muscles. Internal rotation is controlled by the Subscapularis, external rotation is controlled by the Infraspinatus and Teres Minor, and the Supraspinatus initiates abduction of the arm. The tendons of these four muscles come together to form a capsular support that holds the ball of the humerus joint in the socket of the shoulder blade. Thus, the stronger the Rotator Cuff muscles are, the more stability at the ball and socket.

The primary factor of Rotator Cuff problems is weakness. I don’t mean general weakness. You may be able to do push ups and pull ups without pain but still get pain in the upper arm with certain movements. I am referring to specific weakness of the Rotator Cuff. It tends to be the case that our general upper body exercises strengthen our large movers like the chest, biceps, triceps, but demand support from our Rotator Cuff muscles. So as the larger muscle groups get stronger, the supporting Rotator Cuff muscles don’t get the same strengthening in the supporting role. Eventually as our stronger larger muscles push us forward in our exercises by either increase of weight or repetitions our supporting Rotator Cuff muscles can’t keep up with the increased intensity. Eventually we reach a point where we are doing more than our Rotator Cuff muscles can support and the muscles react with either inflammation and/or tightness.

The secondary factor for Rotator Cuff problems is posture. The typical computer posture with our head and shoulders forward is a position of mechanical inefficiency and decreased stability. Thus the Rotator Cuff muscles have to work harder in a poor posture position. 

The solution is to improve posture and strengthen the Rotator Cuff muscles. It is a simple solution but not necessarily easy to do. Correcting posture takes consistency. Strengthening takes consistency and sensitivity. Sensitivity because someone with Rotator Cuff tendinitis or tendinosis can’t just go to the gym and start exercising like everyone else at the gym. Depending on the state of the injury unguided exercising could make the condition worse. 

In summary: If you have an ache in your upper arm due to Rotator Cuff tendinitis or tendinosis the first thing to do is to start improving your posture. Posture is a long term project that won’t give you immediate results, but keep working on it because it will pay off in the long run. The second course of action is to strengthen the Rotator Cuff muscles. Look up external and internal rotation exercises for the Rotator Cuff on the internet and start with relatively light weight. If you can do the exercises without increased pain then continue. If you are not sure that you are doing the right thing or making things worse, consult your physical therapist.

Submit your questions for future PT Perspective columns to Jason Lau, Doctor of Physical Therapy at