Lower Limb Structure
The lower limbs of humans consist of the paired appendages called the legs. Each leg is made up of an upper leg, lower leg, and the foot.
The upper portion of the leg begins at the junction with the pelvic girdle. From the girdle region a bone called the femur inclines downward to the knee joint. The inclination of the femur brings the knees in line with the center of gravity of the body. The femur is the longest and strongest bone in the body. It is a nearly perfect cylinder. At its top end the femur is ball-shaped, so as to fit into the socket of the pelvic girdle. Near the ball-shaped region, the femur flares upward before the main part of the bone descends. The two protrusions that are present are known as the trocanters. They provide leverage for the muscles that manipulate the thigh. The body of the femur (also known as the shaft or the corpus femoris) is strengthened along its length by a ridge (the linea aspera) running down the bone. Testing has demonstrated that the femur is designed to withstand a great deal of stress and load, consistent with its location in a weight bearing part of the body.
Both the front (calf) and the back of the upper leg are well muscled, and supply much of the strength and power for the leg. In athletes, the gastrocnemius and soleus muscles of the calf are often very pronounced. Prominent tendons are also found here. For example, the Tendo Calcaneus is the thickest and strongest tendon in the body.
The knee forms the articulated (capable of movement) joint between the femur and the next lower bone of the leg, the tibia. The knee in protected and stabilized by the patella (also known as the kneecap), a flat, triangular bone. Ligaments and other tissue also help stabilize the knee against excessive side-to-side movement, and cartilaginous material called the meniscus acts to cushion the junction of the femur and the tibia.
The tibia is the second longest bone in the body, after the femur. It extends the length of the lower leg, from the knee to the ankle. It is closely associated with a long and slender bone called the fibula (or calf bone)
The back of the lower leg is also well muscled. The muscles assist in leg and foot motion.
The lower leg connects to the foot. The foot is a complex structure. There are over 20 bones in each foot alone. The foot is also well muscled and is supported by ligaments and tissue known as fascia. Support is of prime importance in the foot, as it bears the weight of the body and must adopt different configurations to permit locomotion.
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