Tendonitis, also called tendinitis, is when a tendon becomes inflamed, often from overuse or injury when moving your body. Tendons are strong, flexible tissues that connect muscles to bones, helping you move. Every time you swing a tennis racket, grab a cup of coffee, go for a run or squat to reach a low cabinet, your tendons are working to make those movements possible.
Your body has around 4,000 tendons. While tendons support your movement, too much strain or repetitive activity can cause them to become inflamed or injured. Tendonitis can happen in different areas of your body, like the heel, shoulder, elbow, ankles or knees.