Tendonitis, more properly termed tendinosis, results from acute or chronic stress of the rotator cuff tendons. Rotator cuff impingement results from repeated irritation of the rotator cuff beneath the acromial arch. 20 Repetitive overhead reaching and weight training are frequent precipitants of rotator cuff tendinosis and impingement. Rotator cuff tendinosis is diagnosed by eliciting pain or weakness with stress testing of the rotator cuff muscles. There are two common tests used for diagnosis of impingement. The Hawkins' test elicits pain with the shoulder passively flexed to 90 degrees and internally rotated. 21 The Neer's test elicits pain with passive abduction of the shoulder to 180 degrees. 22 Radiographs, if obtained, may show calcific deposits in the subacromial space or at the insertion of the supraspinatus tendon to the greater tuberosity. In cases of impingement, curvature of the acromion process may be seen.
I don’t believe that the body can grow strong due to tendon/CNS adaptations as you keep asserting. That may work for a few weeks when you begin a new exercise & improve motor skills and structurally adapt, but it will not last long. You will never get strong in the long run if your muscles are not also growing. But I think many people have vastly overestimated the impact on your appearance that gaining muscle actually has. Gaining 5 lbs of fat will make you appear much sloppier, but gaining 5 lbs of lean muscle will not make that much visual difference while wearing clothes
If non-surgical treatments do not ease symptoms or the shoulder joint is severely worn causing parts of the joint to become loose, a procedure called an arthroplasty may be recommended. This is a joint replacement treatment which involves replacing the ball with a synthetic ball and placing a cap for the scapula (known as a glenoid). After surgery passive shoulder exercises will be carried out and involve another person moving the joint. After 3-6 weeks patients are advised to start exercising the joint independently. Exercises and stretches are an important part of recovery and help to increase strength, flexibility and mobility in the joint. The success of surgery is dependent on the state of the rotator cuff muscles before surgery and the patient’s commitment to the exercise regime.