Picture of Knee Joint

The knee joint is the hinged joint that allows the legs to bend. The upper leg bone (femur) and the larger lower leg bone (tibia) are connected via the knee joint. The kneecap (patella) forms the protective bony covering for the knee joint. A fibrous capsule surrounds the knee joint, and a series of ligaments holds the outside (collateral ligaments) and the inside (cruciate ligaments) of the knee together. The ligaments stabilize the knee. The tibia and femur are cushioned by two pieces of cartilage called the meniscus. The knee joint is surrounded by bursae, which are fluid-filled sacs that protect structures in the knee against friction.