This document provides information about joints and joint injuries. It begins by defining a joint as the area where two or more bones meet, connected by ligaments. There are three types of joints: fixed/immovable joints which prevent movement; slightly movable joints like those between vertebrae which allow slight movement; and freely movable synovial joints like the knee which allow a large degree of movement. The key parts of synovial joints are the articular cartilage, meniscus, ligaments, joint cavity and synovial membrane. Common joint injuries involve wear and tear of bones and cartilage over time or from heavy weight, and tears of ligaments from sudden movements. Injuries often occur in the knee or ankle joints