Bursitis and tendinitis are both common conditions that involve inflammation of the soft tissue around muscles and bones, most often in the shoulder, elbow, wrist, hip, knee, or ankle.
A bursa is a small, fluid-filled sac that acts as a cushion between a bone and other moving parts: muscles, tendons, or skin. Bursae are found throughout the body. Bursitis occurs when a bursa becomes inflamed (redness and increased fluid in the bursa)
A tendon is a flexible band of fibrous tissue that connects muscles to bones. Tendinitis is inflammation of a tendon. Tendons transmit the pull of the muscle to the bone to cause movement. They are found throughout the body, including the hands, wrists, elbows, shoulders, hips, knees, ankles, and feet. Tendons can be small, like those found in the hand, or large, like the Achilles tendon in the heel.