The Thigh, Leg and Foot

THE THIGH

The FEMUR is the heaviest and longest bone in the body, over two skull lengths. The upper end consists of a head and two projections called trochanters. The head is a spherical knob socketed within the acetabulum. The neck slopes downward from the head. (In the-very young the neck of the femur is almost horizontal but slopes as we become adults. In the very old it becomes horizontal again which partly accounts for the loss of height in old age.)

The GREAT TROCHANTER is found at the top of the femoral shaft and can be easily felt at the surface of the hip area. The span between the great trochanters mark the widest point of the male hips but the broadest point is lower in females due to fat deposits.

The LESSER TROCHANTER is towards the back of the shaft lower than the great trochanter. This is an important attachment point for mucscles.

The SHAFT is cylindrical, curving forward and slanted obliquely downward toward the midline. A ridge, the LINEA ASPERA M. rough line), runs down the back of the shaft and is an attachment for muscles. At the lower end the shaft widens to form the MEDIAL and LATERAL CONDYLES, smoothly rounded swellings, which articulate with the TIBIA and medial and lateral EPICONDYLES, small, roughened eminences on the outer condylar surfaces. The condyles and the tibia form a hinge joint, the largest joint in the body. The medial epicondyle is higher and more pronounced; the lateral epicondyle pushes more forward. In front, between the two condyles is a smooth depression into which fits the PATELLA (kneecap).

THE LEG

The leg consists of two bones: TIBIA the larger bone; medial (big toe) side FIBULA slender; lateral (little toe side)

Only the tibia comes in contact with the femur. The fibula articulates passively with the fibula above and below in plane joints.

The head of the tibia is about the same width as the femur but is not quite as deep. About 1 to 1 1/2 inches below the top of the head is a rough prominence: the tuberosity of the tibia. This forms an important anchor for the patella and the quadriceps. Below the head it contracts to a triangular cross-section with a sharp S-curved ridge in front. Along this ridge (tibial crest) the bone is subcutaneous. No muscle crosses this ridge and there is no muscle along the medial side -- just bone beneath the skin.

The inferior end of the tibia widens into a prominence: the medial malleolus, and forms a major part of the joint with the foot. The inner, or medial, malleolus (square in shape), forms the inner side of the ankle. It is higher and more forward than the outer ankle which is formed by the lateral malleolus of the fibula.

The fibula sits slightly to the back of the tibia and, although about the same length as the tibia, starts lower. It is a thin shaft with a head and distal end pointed like an arrowhead.

KNEE: hinge joint -- made up of two major bones: the distal end of the femur and the head of the tibia. When the leg is bent the bottom surface of the femur becomes subcutaneous.

The leg cannot bend forward past a straight line because of ligaments stabilizing the joint. The collateral ligaments, linking the inner and outer epicondyles of the femur to the tibia and fibula respectively, help prevent forward extension of the leg. No rotation of the leg is possible when it is straight but some is possible when the leg is bent because the fibular collateral ligament is more relaxed in flexion.

The PATELLA is roughly five-sided. It forms the anchor for the large muscles of the front of the thigh. When the leg is straight (extended) the base of the patella is at or slightly above the knee joint. In flexion the patella is pulled down to shield the exposed intercondylar space. The patella is engulfed by the broad strap of the quadriceps tendon.

 

CONSTRUCTION POINTS AND LINES OF THE THIGH AND LEG:

THE FOOT

The bones of the foot consist of:

TARSALS (7) like the carpals of the hand they are a loosely-bound mass; two are of particular importance:

the CALCANEOUS (heel bone) extends back of the fibula in an axe-like form andserves as an anchor for the Achilles tendon

the TALUS which articulates with the tibia to form a hinge joint

the METATARSALS which along with the tarsals create the arch of the foot; they are arched both transversely and longitudinally

the PHALANGES -- the big toe has two phalanxes; the other toes, three

The tarsals on the medial side account for about 1/2 the length of the foot and on the lateral side about 1/3 the length.

The metatarsals of the little toe lies about flat on the ground; the metatarsal of the 2nd toe marks the highest point of the transverse arch.

The length of the foot is about 1 head from the heel to the tip of the little toe.

The calcaneous varies in the amount of projection backwards and this affects the thickness of the ankle from a side view.

The arch of the foot is centered on the line of gravity.

CONSTRUCTION POINTS OF THE FOOT:

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