Tendonitis is inflammation, irritation, and swelling of a
tendon, which is the fibrous structure that joins muscle to bone. While Tendonitis can
effect any tendon it is not common to find Tendonitis in the deltoid tendon.
The deltoid muscle is a large triangular muscle covering
the shoulder joint and serving to abduct and flex and extend and rotate the arm.
Most often pain in the shoulder has to do with the Rotator Cuff muscles or arthritis in
the shoulder joint.