This is a problem with a tendon in your shoulder. Most often, it’s the “long head of biceps” tendon. It travels from the front of your upper arm to the top of your shoulder socket. With this condition, the tendon becomes painfully inflamed or irritated.
Biceps tendonitis is usually caused by normal wear and tear. It can be a problem for people who perform repetitive shoulder movements. It can be a problem for people who play tennis or baseball, and for swimmers. Over time, these activities can damage your shoulder’s tendon. It can become red and swollen. The covering around it, called the “tendon sheath,” can thicken.