The knee is a complex joint that connects the thigh bone to the shin bone. It allows for bending and straightening of the leg, enabling activities like walking, running, and jumping. The knee is made up of bones, cartilage, ligaments, and tendons, which work together to provide stability and movement. The knee joint is surrounded by a capsule filled with synovial fluid, which lubricates the joint and reduces friction. Common injuries to the knee include ligament tears and cartilage damage, often resulting from sports or accidents. Proper care and strengthening exercises can help maintain knee health.