Mobility of the legs, stability and coordination of human movements – all this would be impossible without the lower leg. The part of the leg, located between the knee and ankle joints, is the most important functional department in the anatomy of the musculoskeletal system. The bone and muscular systems of the lower leg, developed in accordance with age norms, are the basis that provides most of the physical activity, including walking, running and other movements of the body in space. Let’s figure out how the human lower leg works, what its functionality depends on and how they can be improved.
Table of Contents
The anatomical structure of the shin bones
The bone system of the lower leg is arranged rather primitively and includes only two large bones – the tibia and the fibula. Both of them are quite durable, as they are partially responsible for maintaining the human body in an upright position, shape the gait and serve as a support for the body.
The tibia is larger, since it serves as a supporting one. The expansion in the upper part, forming two condyles, serves as an articulation point with the large femur, forming the knee joint. Here, but a little more laterally, there is another condyle, due to which the tibia and fibula are united into a single bone system.
The body of the tibia has the shape of a triangular prism with a base on the back side. The inner and outer sides of the bone form an acute angle – the front edge of the bone, which, if desired, can be felt with a slight pressure on the surface of the leg. In the upper part of the anterior edge, in the popliteal region, a pronounced tuberosity is formed, to which the most powerful tendons and muscles of the lower leg are attached.
The lower end of the bone also expands towards the base, forming a prominent protrusion – the medial malleolus. The bumpy surface of the base connects to the bones of the foot, forming the ankle joint.
Compared to the tibia, the peroneal bone appears thin and fragile. In fact, this is not entirely correct: although it is much narrower, its density is not inferior to that of the tibial. In the upper part, the peroneal bone has a head, which, coinciding in size with the lateral condyle of the tibia, forms a strong articulation.
The lower part of the fibula also expands to form the lateral malleolus. It protrudes noticeably above the surface of the lower leg, so it can be easily felt without even straining the leg.
Features of the articulation of the bones of the lower leg
The tibia and fibula are connected from above by means of a flat joint belonging to the group of inactive. This joint is additionally immobilized by a rather strong ligamentous apparatus that holds the complex. Along the entire length of the tibia, an interosseous membrane is located between the bones, which turns downward into syndesmosis, connecting the lower ends of the tibia and fibula.
Calf muscles: anatomy, classification and function
The bony structures of the lower leg are surrounded by a dense ring of muscles, thanks to which the leg remains mobile, from the foot to the knee. Depending on the location, all muscles are classified into three separate groups: anterior, posterior and lateral. The anterior group of muscle fibers is responsible for supination, extension and adduction of the foot, as well as extension of the toes. The back group acts as an antagonist and controls flexion of the foot and toes. And the muscles belonging to the lateral group control abduction, pronation and flexion of the foot.
The tibialis anterior muscle is located throughout the leg, starting in the upper part of the interosseous membrane and ending on the medial wedge-shaped and first metatarsal bones of the foot. Its functions are to extend and supination of the foot. In the area of the ankle, it is crossed by the upper and lower ligaments, which hold the extensor tendons. The muscle body is easily felt on the front surface of the lower leg, especially in the area of the transition to the ankle joint, where its tendon bulges noticeably with increased foot extension.
The long extensor of the toes is a polyarticular muscle that begins at the upper edge of the tibia and fibula and, dividing into four tendons on the surface of the foot, attaches to the distal phalanges of 2–5 toes. And although the main function of this muscle is to extend the toes, it is also partially involved in the extension and pronation of the foot.
The extensor longus of the thumb is the smallest and weakest muscle in the group under consideration. It begins in the lower part of the lower leg and is fixed on the surface of the distal phalanx. In addition to extension of the big toe, this muscle is involved in supination and extension of the foot.
The peroneal longus muscle completely covers the bone of the same name, covering the lateral malleolus from above and fixing itself between the outer surface of the fibula and the first metatarsal bone. In the area of transition to the calcaneus, it is held by a dense weave of ligaments (lower and upper tendon retainers). Thanks to this muscle, a person can perform flexion, abduction and pronation of the foot.
The peroneus shortis muscle serves as an agonist for the peroneus longus, responsible for pronation, abduction and flexion of the foot. It originates at the interosseous septum, bends around the ankle from below and is fixed at the fifth metatarsus.
The triceps muscle is the most powerful and voluminous among the muscles of the lower leg. It is located on the back surface and forms the so-called calves – a bulging part, especially developed in athletes. Two of the three heads – the medial and lateral gastrocnemius – are located superficially, and the third – soleus – lies in deep layers. All three heads of the triceps muscle are combined into one unit at the calcaneus, forming the Achilles, or calcaneus, tendon. The functions of the triceps muscle are extremely multifaceted. The calf heads flex the knee and ankle joints, and the soleus flexion the foot. In addition, the heads of the gastrocnemius muscle take part in the formation of the rhomboid popliteal fossa, through which the main nerve bundles and vessels that feed the thigh and lower leg pass.
The plantar muscle is rudimentary, therefore it does not always appear in the anatomy of the lower leg. It begins at the knee joint and goes down, running slightly medial to the center. In the lower part of the lower leg, the muscle is transformed into a thin longitudinal ligament, which lies in the thickness of the triceps muscle, between the soleus and gastrocnemius heads. Descending to the calcaneus, the ligament of the plantar muscle is woven into the Achilles tendon, forming a single complex.
The popliteal muscle is adjacent to the posterior plane of the knee joint. It has a short flat shape and is partially fixed at the articular capsule of the knee, which allows it to pull the capsule wall at the moment of bending the leg. In addition, the popliteal muscle is involved in flexion and pronation of the lower leg.
The tibialis posterior muscle adjoins directly to the bone structures and is hidden under the triceps body. Together with the inner wall of the soleus muscle, it forms a narrow ankle-popliteal canal through which the main part of the blood vessels and nerve fibers of the lower limb passes. Also, the tibialis posterior muscle plays the role of the flexor and instep support of the foot.
The long flexor of the fingers is an antagonist of the extensor, which belongs to the group of the anterior muscles of the lower leg. This muscle begins at the posterior wall of the tibia, divides into four tendons and attaches to the plantar surface of the distal phalanges of 2–5 toes. The functional of the long flexor affects not only the fingers, but also the foot: thanks to the coordinated contraction of this muscle, the ankle is flexed and supined.
The long flexor of the thumb is the strongest among the deep posterior muscles. It connects the lower part of the fibula and the distal phalanx of the big toe, causing flexion of the foot and the toe itself during contraction.
Strengthening the muscles and bones of the lower leg
Despite the high functionality, the anatomy of the lower leg is quite simple. This part of the lower limbs is easy to train, thanks to which you can significantly strengthen the muscular frame of the human body. The calf muscles, especially the back ones, can become much stronger even with regular walking, not to mention special exercises aimed at developing the legs. Jogging and walking at a fast pace, gymnastics, yoga or athletics – all this allows you to develop the legs, make them more stable and strong, which can subsequently save you from problems with the musculoskeletal system.
In addition, a healthy lifestyle, regular walks in the fresh air, especially on a cloudless day, when under the influence of sunlight, the body can receive an additional dose of vitamin “D” , as well as proper nutrition, rich in vitamins and minerals. To keep your bones strong and able to handle high loads, eat the following foods:
chia seeds, sesame seeds, cabbage, figs, turnips, spinach, white beans, almonds are the main sources of calcium;
corn, barley, oats, wheat, broccoli, beans, pumpkin and sunflower seeds, rich in phosphorus;
almonds, cashews, spinach, bran, sweet potatoes, beans, thanks to which you can fill the magnesium deficiency;
seaweed, chanterelles and yeast are food sources of calciferol;
leafy vegetables, cabbage, green tomatoes and lettuce – they contain vitamin K.
And, of course, it is worth taking into account the water balance in the cells of the body, because without enough fluid, the muscles will quickly weaken and lose elasticity. By following these recommendations, you will be able to keep your shins in perfect physical shape, which will serve as an excellent prevention of diseases of the musculoskeletal system.