Causes of Shoulder Tendonitis
Tendinitis occurs as a result of sports injuries, by repetitive minor impact on the affected area, or from a sudden, more serious injury. For instance, professional baseball players, swimmers, tennis players, and golfers are susceptible to tendinitis in their shoulders, arms, and elbows. Improper technique in any sport is one of the primary causes of overload on tissues including tendons, which can contribute to tendinitis.

You don’t have to be a professional athlete to develop this condition, however. People with jobs that require overhead work (such as assembly work or an overhead pressing machine), and heavy lifting are at risk of tendinitis. A direct blow to the shoulder area or falling on an outstretched arm can also cause shoulder tendinitis.