Understanding How the Knee Works A joint is formed by two or
more bones that are connected by thick bands of tissue called
ligaments. The knee is the largest joint in the body and is made
up of three main parts: - The lower end of the thigh bone, or
femur. - The upper end of the shin bone, or tibia. - The
kneecap, or patella. The thigh bone (femur) turns on the upper
end of the shin bone (tibia), and the kneecap (patella) slides
in a groove on the end of the thigh bone. Ligaments, which are
bands of tissue, connect the thigh bone and the shin bone to
help keep the knee joint steady. The quadriceps, the long
muscles on the front of the thigh, help strengthen the knee. A
smooth substance called articular cartilage covers the surface
of the bones where they touch each other within the joint. This
articular cartilage acts as a cushion between the bones. The
rest of the surfaces of the knee joint are covered by a thin,
smooth tissue liner called synovial membrane, which makes a
small amount of fluid that acts as a