My left shoulder has had pain it sometimes shoots down into the arm. the tendons around the joint are tender. its like aching pain bu not always there?

Rotator cuff: Depending on your age could be chronic tendinosis or even a rotator cuff tear. Rotator cuff pain often radiates down side of arm. In patients under forty to fifty this is often the result of tendinopathy or mild degeneration and will usually respond to nonoperative measures. Older patients often have a rotator cuff tear which depending on severity is sometimes best managed with surgery.

Biceps tendonitis: It sounds like either biceps tendonitis or rotator cuff tendonitis. Either shoulder problem can cause radiating pain into the arm area. Obviously an orhopedic exam would help localize the pain etiology. Also the cervical spine should be checked to make sure that there is no cervical radicular component to the problem which would also cause radiating symptoms into the arm.