Anatomy & Organs

Leg – structure, function & diseases

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The word leg can describe two things: In ancient language, each bone was a “leg” (as in “bones”), but today the term is actually only used to describe the lower extremities of the human body. The following is a brief overview of the anatomy of the leg, which can help to better understand the various ailments and diseases that almost everyone will experience at some point in their life.

What are the legs

The leg in a 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 (depending on the definition also belonging to the torso), thigh , lower leg and foot. Three large joints connect these four sections with each other, but there are many other small joints, especially in the foot.

Anatomy & Structure

From an anatomical point of view, a leg (ignoring the pelvis) consists 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 bears the main weight , and calf bone (fibula) which carries part of the load on the side and has a slight flexibility in movement; in between is the kneecap (patella), which enables gentle movement of the knee joint and is the starting point for the large thigh muscles.The tarsal bones, the talus and heel bone, as well as the navicular bone, the three cuneiform bones and the cuboid bone are added to the foot. The five metatarsal and toe bones form the end of the foot, 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 the structure and function and are also of crucial importance for the doctor in the physical examination. From top to bottom, these are primarily the “trochanter (major)” as a palpable hump just below the hip joint (point of reference for injections), the kneecap (can luxate, i.e. jump out of its compartment and then usually hangs to the side), the outer hump of the shinbone and the edge of the shinbone (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 malleolus (medical “malleolus” , swells at theligament tear and is then no longer palpable), the heel bone (tender on pressure with ” heel spurs “), the outer metatarsal bones (tendon attachment pain and bone fractures ) and the individual toe bones.

All other bones are surrounded by muscles, more or less fatty tissue and skin and are protected by them. Most of the vascular and nerve tracts are also well padded deep in the soft tissue, since pressing them down or even severing them would have fatal consequences for the part of the leg underneath. There are superficially palpable pulses only in the groin, in the hollow of the knee, below and behind the inner malleolus and on the back of the foot.

Functions & Tasks

Put simply, the function of the leg is the locomotion of the body, in the case of humans even when walking upright. In order to make this possible, a highly sophisticated interplay between the foot muscles (especially when standing on one leg), leg muscles, pelvic muscles, the spine and sometimes, to compensate, the arms is required .

Humans usually learn this interaction during the first year and a half of life, after that it happens automatically, so we don’t have to constantly concentrate on it. Basically, it is a very complex job that the brain performs here as a matter of course: Nerve impulses from the skin , muscles and joints constantly give feedback about their touch receptors, joint position, muscle stretching status and so on.

Much runs as an automated reflex at the level of the spinal cord and is “sent back” directly as a motor response to the place of origin, but much is also modulated and regulated by the cerebellum and cerebrum, where not only stored movement patterns are executed, but of course also the eye and vestibular system important word “have a say”.

Diseases & Ailments

This is precisely why it is so important that the nerves in the leg function well: If they are disturbed by long-term elevated blood sugar levels (diabetes), injuries (broken bones with nerve tear) or pressure damage ( herniated discs , positioning damage), the person loses their sense of touch.In diabetics, this first happens on the soles of the feet, there is constant tingling, and small injuries are no longer noticed and permanently lead 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 the entire nerve supplying the leg at the point where it exits the spinal cord .

The blood supply to the leg is also a frequent cause for concern and torments many people, especially in old age: Atherosclerosis caused by age, smoking , malnutrition, obesity and high blood pressure damages not only the coronary arteries ( heart attack ) and cerebral vessels ( stroke ) but also the blood supply to the leg and leads to the so-called ” window display disease” PAVK (peripheral arterial occlusive disease):

After just a few steps, those affected experience pain in their legs because the muscles can no longer be supplied with sufficient blood, and they therefore first stand for a few minutes at each shop window until the pain subsides. In more advanced stages, parts of the leg can also die off.

In addition to these two “internal” main diseases of the leg, there are of course still a lot of broken bones, torn muscle fibers , torn ligaments and overload complaints that affect the leg and especially young people and athletes. In older age, arthrosis of the hip and knee joint is a frequent accompaniment, which can lead to considerable pain and limitations in mobility and quality of life.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.