Tendons are pieces of connective tissue that bind your muscles to bones. Like any part of the body, injury or overuse can lead to pain or inflammation in your tendons. This condition is called tendinitis. Biceps tendinitis is most often the result of everyday wear and tear on the muscle. In terms of sports, weightlifting is one of the high risk activities for biceps tendinitis, but this condition is a common sports injury that can happen to pros and amateurs alike.