Anatomy of Human Legs
The human leg is the entire lower extremity or limb of the human body, including the foot, thigh and even the hip or gluteal region, the precise definition in human anatomy refers to the section of the lower limb extending between the knee and the ankle.
Legs are used for standing, walking, jumping, running, kicking, and similar activities, and constitute a significant portion of a person's mass.
In human anatomical terms, the leg is the part of the lower limb that lies between the knee and the ankle,[6] the thigh is between the hip and knee and the term "lower limb" is used to describe the colloquial leg. This article generally follows the common usage.
The leg from the knee to the ankle is called the cnemis (née'mis) or crus. The calf is the back portion and the shin is the front.
Comparison between human and gorilla skeletons. (Gorilla in non-natural stretched posture.)
Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism is not limited to the leg, however, but has also affected the location of the body's center of gravity, the reorganisation of internal organs, and the form and biomechanism of the trunk. In humans, the double S-shaped vertebral column acts as a shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization to support and locomotion — in orangutans the leg length is 111% of the trunk; in chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.[7]
See also: Human skeletal changes due to bipedalism
[edit] Skeleton
Bones of the leg
The major (long) bones of the human leg are the femur (thighbone), tibia (shinbone), and fibula (the smaller, rear calf bone). The patella (kneecap) is the bone in front of the knee. Most of the leg skeleton has bony prominences and margins that can be palpated, notable exceptions being the hip joint, and the neck and shaft of femur. Many of these anatomical landmarks are used to define the extent of the leg: most notably the anterior superior iliac spine, the greater trochanter, the superior margin of the medial condyle of tibia, and the medial malleolus.
In the normal case, the large joints of the lower limb are aligned on a straight line which represents the mechanical longitudinal axis of the leg, the Mikulicz line. This line stretches from the hip joint (or more precisely the head of the femur), through the knee joint (the intercondylar eminence of the tibia), and down to the center of the ankle (the ankle mortise, the fork-like grip between the medial and lateral malleoli). In the tibial shaft, the mechanical and anatomical axes coincide, but in the femoral shaft they diverge 6°, resulting in the femorotibial angle of 174° in a leg with normal axial alignment. A leg is considered straight when, with the feet brought together, both the medial malleoli of the ankle and the medial condyles of the knee are touching. Divergence from the normal femorotibial angle is called genu varum if the center of the knee joint is lateral to the mechanical axis (intermalleolar distance exceeds 3 cm), and genu valgum if it is medial to the mechanical axis (intercondylar distance exceeds 5 cm). These conditions impose unbalanced loads on the joints and stretching of either the thigh's adductors and abductors. The angle of inclination formed between the neck and shaft of the femur, the collodiaphysial angle, varies with age—about 150° in the newborn, it gradually decreases to 126-128° in adults, to reach 120° in old age. Pathological changes in this angle results in abnormal posture of the leg: A small angle produces coxa vara and a large angle in coxa valga; the latter is usually combined with genu varum and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles results in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of mobility.
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Legs are used for standing, walking, jumping, running, kicking, and similar activities, and constitute a significant portion of a person's mass.
In human anatomical terms, the leg is the part of the lower limb that lies between the knee and the ankle,[6] the thigh is between the hip and knee and the term "lower limb" is used to describe the colloquial leg. This article generally follows the common usage.
The leg from the knee to the ankle is called the cnemis (née'mis) or crus. The calf is the back portion and the shin is the front.
Comparison between human and gorilla skeletons. (Gorilla in non-natural stretched posture.)
Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism is not limited to the leg, however, but has also affected the location of the body's center of gravity, the reorganisation of internal organs, and the form and biomechanism of the trunk. In humans, the double S-shaped vertebral column acts as a shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization to support and locomotion — in orangutans the leg length is 111% of the trunk; in chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.[7]
See also: Human skeletal changes due to bipedalism
[edit] Skeleton
Bones of the leg
The major (long) bones of the human leg are the femur (thighbone), tibia (shinbone), and fibula (the smaller, rear calf bone). The patella (kneecap) is the bone in front of the knee. Most of the leg skeleton has bony prominences and margins that can be palpated, notable exceptions being the hip joint, and the neck and shaft of femur. Many of these anatomical landmarks are used to define the extent of the leg: most notably the anterior superior iliac spine, the greater trochanter, the superior margin of the medial condyle of tibia, and the medial malleolus.
In the normal case, the large joints of the lower limb are aligned on a straight line which represents the mechanical longitudinal axis of the leg, the Mikulicz line. This line stretches from the hip joint (or more precisely the head of the femur), through the knee joint (the intercondylar eminence of the tibia), and down to the center of the ankle (the ankle mortise, the fork-like grip between the medial and lateral malleoli). In the tibial shaft, the mechanical and anatomical axes coincide, but in the femoral shaft they diverge 6°, resulting in the femorotibial angle of 174° in a leg with normal axial alignment. A leg is considered straight when, with the feet brought together, both the medial malleoli of the ankle and the medial condyles of the knee are touching. Divergence from the normal femorotibial angle is called genu varum if the center of the knee joint is lateral to the mechanical axis (intermalleolar distance exceeds 3 cm), and genu valgum if it is medial to the mechanical axis (intercondylar distance exceeds 5 cm). These conditions impose unbalanced loads on the joints and stretching of either the thigh's adductors and abductors. The angle of inclination formed between the neck and shaft of the femur, the collodiaphysial angle, varies with age—about 150° in the newborn, it gradually decreases to 126-128° in adults, to reach 120° in old age. Pathological changes in this angle results in abnormal posture of the leg: A small angle produces coxa vara and a large angle in coxa valga; the latter is usually combined with genu varum and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles results in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of mobility.
