There are three major bones of the human leg. The kneecap is also a bone, so there are actually four bones in the human leg, but the major bones are the femur in the thigh and the tibia and fibula of the lower leg. These bones support the weight of the body during walking, running and other actvities. The patella (kneecap) provides protection for the knee joint.
The Upper Leg
The upper leg is called the thigh. The femur is the bone in the thigh. The femur articulates (forms a joint with) the acetabulum of the pelvis to form the hip joint and the tibia of the lower leg to form the knee. The femur is the longest and largest bone of the body. It has a rounded head that is offset at an angle from the main shaft of the bone.
There are two major bony protrusions where the angle is formed called the greater and lesser trochanter. These trochanters are where the muscles of the hip and groin attach to the femur.
At the knee, there is a wide and somewhat flattened area that forms a joint with the tibia. There are also two bony masses on either side of the knee joint where ligaments connect to stabilize the knee, called the epicondyles.
The Kneecap
The kneecap, or patella, is a special type of bone, called a sesimoid bone, that forms inside a tendon. The patellar tendon is located on the front of the knee and provides the connection between the muscles that straighten the knee and the lower leg at the tibial tuberosity. The patella protects the knee joint when the leg is flexed.
The Lower Leg
The lower leg has two bones: the tibia and fibula.
The tibia is the larger of the two bones and has joints at both the knee and ankle. At the knee, the tibia has a large flat area called the tibial plateau where the femur sits to form the knee joint. There are several ligaments that stabilize this joint, including the collateral, cruciate and patellar ligaments. There is a large bony bump on the front of the knee called the tibial tuberosity where the patellar ligament connects. At the ankle, the tibia has a flattened area and a small pointed projection. This forms the greater portion of the ankle joint where the tibia and tallus articulate.
The other bone of the lower leg is the fibula. Near the knee, it is small and has a relatively fixed joint with the tibia below the tibial plateau. At the ankle, the fibula has a larger head that, together with the tibia, forms a sort of yoke making the ankle joint stable. The tibia and fibula are joined along their length by a wide, flat tendon called the interosseous membrane, which keeps the bones tightly bound together and provides stability to the ankle joint.
References
- "Gray's Anatomy: The Anatomical Basis of Clinical Practice"; Susan Standring (Editor); 2008
- "Trail guide to the body: how to locate muscles, bones and more"; Andrew Biel; 2005
