"Bursitis and tendinitis are both common conditions that cause swelling around muscles and bones. They occur 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 body parts such as muscles, tendons, or skin. Bursae are found throughout the body. Bursitis occurs when a bursa becomes swollen.
A tendon is a flexible band of tissue that connects muscles to bones. Tendons can be small, like those found in the hand or ankle, or large, like the Achilles tendon in the heel. Tendons help create movement by making the muscles push or pull the bones in different ways. Tendinitis is the severe swelling of a tendon." as retrieved from:
The National Institute Arthritis and Musculoskeletal and Skin Diseases