The word leg can describe two things: In ancient language, each bone was a “leg” (as in “bones“), but today the term is really only used to describe the lower extremity of the human body. The following is a brief overview of the anatomy of the leg, which may help to better understand the various ailments and diseases that probably affect almost everyone at some point in their lives.
What are the legs?
The leg in the broader sense, referred to in medicine and anatomy as the “lower extremity” (as opposed to the arm as the “upper extremity), can be casually divided into four sections:
Pelvic girdle (also part of the trunk, depending on the definition), thigh, lower leg, and foot. Three large joints connect these four sections, but many more small joints are found, especially on the foot.
Anatomy and structure
Anatomically, a leg (if you leave out the pelvis for once) is composed of 30 bones: The thigh bone (femur) is the longest and largest bone in the human body, the lower leg consists of the shin bone (tibia), which carries the main weight, and the fibula (fibula), which carries part of the load to the side of it and has a slight flexibility in movement; between them is the kneecap (patella), which allows a smooth movement of the knee joint and is the attachment point of large thigh muscles. On the foot, there are the tarsal bones, the talus and calcaneus, as well as the navicular bone, the three cuneiform bones and the cuboid bone. The foot is completed by the five metatarsal bones and the toe bones, of which there are two on the big toe and three on each of the other toes. Bone points on the leg that can be felt from the outside provide information about structure and function and are also of decisive importance for the physician in the physical examination. From top to bottom, these are primarily the “trochanter (major)” as a palpable bump just below the hip joint (a clue for injections), the kneecap (can luxate, i.e. pop out of its socket and then usually hangs to the side), the outer cusps of the tibia and the edge of the tibia (well supplied with nerves and therefore very sensitive to pain), the hump at the upper end of the fibula (on the outside just below the knee joint, very susceptible to pressure damage due to a superficial nerve course), inner and outer malleoli (medically “malleolus”, swells when a ligament is torn and is then no longer palpable), the calcaneus (pressure painful in the case of “heel spurs”), the outer metatarsal bones (tendon attachment pain and boil fractures) and the individual toe bones. All other bones are surrounded by muscles, more or less fatty tissue and skin and are protected by these. The vascular and nerve pathways are also largely well cushioned in the depths of the soft tissue, since their compression or even severance would have fatal consequences for the underlying part of the leg. Superficially palpable pulses exist only in the groin, in the popliteal fossa, under-hind the medial malleolus, and on the dorsum of the foot.
Functions and tasks
Simply put, the function of the leg is the locomotion of the body, in the case of humans even in an upright gait. In order to make this possible, it requires a precisely sophisticated interplay between foot muscles (especially when standing on one leg), leg muscles, pelvic muscles, spine and sometimes, for balance, the arms. Humans normally learn this interaction during the first year and a half of life, after which it happens automatically, so we don’t have to focus on it all the time. Basically, it is a very complex job that the brain performs here quite naturally: Nerve impulses from the skin, muscles and joints constantly provide feedback about their tactile receptors, joint position, muscle stretching state and so on. Much of this takes place as an automated reflex at the spinal cord level and is “sent back” directly to the point of origin as a motor response, but much is also modulated and regulated by the cerebellum and cerebrum, where not only stored movement patterns are executed, but of course the eye and the organ of equilibrium also have an important “say”.
Diseases and ailments
This is precisely why it is also so important that the nerves of the leg function well: If they are disturbed by long-term elevated blood sugar levels (diabetes), by injuries (bone fractures with nerve rupture) or pressure damage (herniated discs, positional damage), the person loses his sense of touch. In diabetics, this happens first on the sole of the foot, there is constant tingling, and small injuries are no longer noticed and lead permanently to major soft tissue damage and bone infections. In the case of a herniated disc, sensory and motor deficits are in the foreground, since the disc in the lumbar spine squeezes off the entire nerve supplying the leg already at its exit point from the spinal cord. The blood supply to the leg is also often a cause for concern and torments many people, especially at an advanced age: arteriosclerosis, caused by age, smoking, malnutrition, obesity and high blood pressure, damages not only the coronary vessels (heart attack) and cerebral vessels (stroke) but also the blood supply to the leg and leads to the so-called “showcase disease” PAVK (peripheral arterial occlusive disease):
After just a few steps, sufferers get pain in their leg because the muscles can no longer be supplied with sufficient blood, so they stop at each storefront for a few minutes until the pain subsides. In more advanced stages, parts of the leg may also die. In addition to these two main “internal” diseases of the leg, there are of course plenty of bone fractures, torn muscle fibers, torn ligaments and overuse complaints that affect the leg and especially young people and athletes. At older ages, on the other hand, osteoarthritis of the hip and knee joints is a common companion that can lead to significant pain and limitations in mobility and quality of life.
