Tendonitis involves the inflammation of a tendon and its surrounding ligaments, often because of overuse. Tendonitis on the outside of the elbow is called tennis elbow; tendonitis on the inside of the elbow is called golfer's elbow. The first phase of treatment for tendonitis is rest, so if you have tennis or golfer's elbow, don't swim until your elbow is free of pain. When you resume swimming, let your body be your guide: if it hurts, don't do it.
Take an over-the-counter anti-inflammatory medication before swimming. This helps protect your tendon from swelling while you exercise.
Consult a trainer about modifications to your swimming technique. Until you are fully healed, you should avoid putting much pressure on your elbow. A swim trainer can help you make changes that will protect your injured joint.
Stretch your wrist and elbow gently before you enter the pool. Stretching helps you maintain flexibility and reduces your risk of reinjuring yourself.
Return to swimming carefully and gently. Build strength in the injured elbow slowly, without rushing yourself. If a stroke hurts, stop doing it.
Stretch again when you exit the pool. Elongate the muscles and tendon to prevent inflammation and stiffness.