Most children know that the shinbone hurts like hell when someone kicks it. This is due to the fact that it is relatively unprotected for bone conditions directly under the skin. Yet it is an important bone of the body, without which we could never stand upright.
What is the tibia?
The tibia is one of the two bones of the lower leg, along with the fibula, and thus connects the femur to the tarsal bones. It is a typical tubular bone with a contiguous medullary cavity. Bounding joints are the knee and the ankle, and there is also a rather rigid articulated connection between the tibia and fibula.
Anatomy and structure
A comparison of anatomy can illustrate the importance of the tibia to the lower extremity, or legs: Whereas on the forearm the ulna and radius are functionally about equally important as bones running side by side, on the lower leg the weight is clearly shifted (even literally) in favor of the tibia. The tibia transfers the bulk of the body load from the knee joint to the upper ankle joint. The fibula runs laterally from it and serves only as a muscle origin and suspension in the upper ankle joint. The fibula also has no direct relationship to the knee joint: it is merely composed of the femur, tibia and patella. Only the upper ankle joint is formed by the tibia and fibula as the ankle fork and the ankle bone as the joint partner, whereby the tibia also has the significantly larger contact surface here. On the X-ray image, there are further anatomical reference points of the tibia, which are of importance to the physician: The condyles as the upper articular cartilages at the knee joint, the tuberosity at the top front as the attachment point for the patellar tendon of the kneecap, the anterior edge of the tibia, whose periosteum is not covered by muscles or other soft tissues and that is why it hurts so hellishly on external contact, and the internal malleolus, which belongs to the ankle joint, are the most important of these bone structures. Between the tibia and fibula, the entire length of the so-called membrana interossea, a tendinous membrane, is stretched, which divides the lower leg into two compartments, in front of and behind the bones. Muscles of the posterior thigh as well as the medial adductors attach primarily to the inner side of the tibia directly below the knee joint. The front and back of the tibia are then the points of origin for the anterior and posterior lower leg muscles, which bridge the ankle joint on the inside behind the ankle and on the outside mostly in front of it with sometimes very long tendon cords, and enable the mobility of the foot. All the major blood vessels and nerve tracts come through the popliteal fossa and then divide, with some piercing the membrana interossea and supplying the front of the lower leg and the dorsum of the foot, while the greater part runs hidden behind between layers of muscle and ends only in the sole of the foot and the toes.
Function and tasks
The function of the tibia is really just to provide stability. Therefore, it is a very strong bone, without which the upright stance and gait would be completely impossible. In addition, it serves as an attachment and origin point for muscles and forms the joint surfaces with the thigh and ankle bone. In addition, we must not forget its role as a “venue” for blood formation, which, as in all long bones, takes place in its marrow.
Diseases and ailments
In the tibia, as is the case with all bones, various diseases and injuries can develop. The most common are certainly the tibia fractures: the tibia head fracture just below the knee happens in this case, especially with longitudinal compression of the leg. The tibial shaft fracture usually happens together with a fracture of the fibula, typical accident mechanisms are fall while skiing or when a pedestrian is hit by the bumper of a vehicle at the appropriate height. Moreover, because of the superficial location of the bone structures, these are often open fractures. Meanwhile, one of the most common fractures of the human body in general is the ankle fracture, at the very bottom of the tibia or fibula. They all usually have to be stabilized surgically.It should also be mentioned that due to the division of the lower leg into narrow compartments by the membrana interossea mentioned above, pressure situations can quickly arise after injuries: After a fracture, tissue always swells, the heart continues to pump blood downward toward the foot, which cannot flow back due to the increased pressure and cannot escape from the respective compartment due to the stable membranes. Severe pain and slow death of the lower leg are the result, rapid action and splitting of the fascia (creating space) is required. Pain in the tibia can also be, especially in children and adolescents, once so-called aseptic bone necrosis or benign and malignant tumors of the bone. A clarification, if necessary by means of X-ray imaging, is always indicated, especially if no accident is remembered.
