The Anatomy of the Tibia

The tibia is the main long bone of the lower leg. It is commonly known as the shin bone and is felt easily along the anterior (front) of the leg below the knee. The tibia is about 36 cm long on average.

Tibial malformations are noticeable defects of the lower limb that may come in several varieties. In an otherwise healthy individual, fractures of the tibia are the most common injury affecting this bone. Pain related to overuse or overtraining can be from stress fractures of the tibia or pain from repetitive impacts known as medial tibial stress syndrome, or "shin splints."

Anatomy

There are two bones in the lower leg, below the knee. The larger of the two bones is the tibia. It is the shin bone and bears the majority of weight between the knee and the ankle. Lateral to (on the outer side of) the tibia is the fibula, a smaller long bone that provides stability and assists with rotation of the ankle.

The tibia is a long bone, which means it is a limb bone that is longer than it is wide. Long bones are found on the upper and lower limbs, fingers, and toes. Long bones contain bone marrow in a cavity running the length of the shaft.

The ends of the tibia have spongy bone, so-called because it contains pockets of circulation and marrow that appear to be sponge-like under a microscope. The entire length of the tibia is covered in a layer of compact bone, which gives the bone its strength.

The top (superior) of the tibia makes up part of the knee and is known as the tibial plateau, upon which the femur rests and together they form the hinge of the knee. It contains two condyles, rounded protuberances that help the tibia fit into the bottom of the femur. The lateral condyle is above the head of the fibula and the medial condyle is opposite. The anterior portion of the top of the tibia is called the tibial tuberosity, where the patella (knee cap) is attached via the patellar ligament.

The bottom (inferior) of the tibia rests on the top and to the medial aspect of the talus. The fibula rests on the lateral portion of the tibia against the fibular notch and extends down over the talus. The three bones make up the largest part of the ankle. The medial portion of the tibia is called the medial malleolus.

Function

All long bones are limb bones that assist with weight-bearing and movement. The bone marrow found in the shaft of all long bones, including the tibia, is mostly red bone marrow, which assists in the production of red blood cells. As a person ages, red bone marrow is replaced with yellow bone marrow made up of mostly fat.

The tibia provides stability and bears weight for the lower leg. It provides leverage for the leg to propel a person through movement and facilitates walking, running, climbing, kicking, etc.

Associated Conditions

There are many conditions that can affect the tibia.

Fracture

The most common injury associated with the tibia is a broken bone. The tibia is positioned at just the right height to be injured by a bumper when a person is struck by a car, making tibia fractures a fairly common traumatic injury. Knee fractures can be of the patella, femur, or tibia and can be caused by either blunt force trauma to the leg or by repetitive impacts such as those caused by running or high impact exercise.

A stress fracture of the tibia is a common injury in runners, gymnasts, and other high-impact athletes. A stress fracture comes from overuse or overtraining and can lead to pain and swelling of the lower leg.

As with all broken bones, the most common symptom of a fractured tibia is pain. There could also be swelling, bruising, or deformity.

Medial Tibial Stress Syndrome

Shin splints is a common condition that affects runners and comes from repetitive impacts of the plantar surface (sole) of the foot on hard surfaces. It is one of the most common causes of pain in athletes, especially long distance runners.

Doctors only have theories to explain the causes and treatments of shin splints. What works for some does not always work for others. Culprits are thought to be weakness or fatigue of the core muscle groups that help with back and abdominal strength.

Many runners believe that the only real cure for shin splints is the prevention of shin splints.

Osteoporosis

Thinning of the bone from osteoporosis can affect all bones in the body and may increase the possibility of a stress fracture. In osteoporosis, bones become more brittle as they lose minerals. Osteoporosis is more common in women than in men.

Paget's Disease of Bone

Paget's disease of bone is the second most common bone disease behind osteoporosis. It is a common condition that interferes with the body's replacement of old bone tissue and can lead to deformities. Like osteoporosis, Paget's disease of bone can lead to an increased possibility of fractures.

Tibial Torsion

The tibia is the main foundation of the lower limb and is mostly responsible for the position and function of the foot and gait. Internal tibial torsion is a congenital birth defect that causes a rotation of the tibia toward the medial aspect. Basically, the tibias rotate inward so that the toes point toward each other. This is often referred to as being pigeon-toed.

A child's doctor will most likely want to monitor the child's progress and development to watch for complications. Braces and other corrective devices are usually not necessary.

Congenital Pseudarthrosis of the Tibia (CPT)

Pseudarthrosis of the tibia is a rare condition that is usually not diagnosed until there is a spontaneous fracture of the tibia. Once the tibia breaks, it is extremely difficult to treat the pseudarthrosis and heal the fracture.

Tibial Hemimelia

Tibial hemimelia is a rare condition affecting the development of the tibia, usually on one limb only. It is a term that covers many different presentations of the tibia, fibula, knee, and ankle. In some cases, the tibia may be bowed, called tibial bowing, with or without bowing of the fibula as well. The tibia could also be malformed or missing.

In some cases of tibial hemimelia, only the distal or proximal end of the tibia is present. The fibula could be larger to compensate and might even have a duplicate fibula present.

There are very few things that can be done to correct tibial hemimelia and are based partly on the overall formation of the tibia and fibula. In many cases, the most appropriate treatment is for amputation and replacement with a prosthesis.

Rehabilitation

Treatment of the various conditions of the tibia is dependant on the condition, but rehabilitation from fractures or medial tibial stress syndrome are the most common.

Tibial fracture treatment is based on the severity and cause of the fracture. A broken tibia from trauma can be treated with a cast and immobilization if the fracture is considered stable (a small crack that is not causing the bone to be displaced).

In cases of the fractured tibia that are not considered stable, the broken bone may have to be surgically repaired and fixated with screws or an external apparatus. Fractures of the shaft of the tibia are often more easily repaired than the complicated fractures of the tibial plateau. Simple fractures of the tibial plateau may heal without surgical intervention.

Rehabilitation of tibial fractures takes anywhere from weeks to months, depending on complications such as the type of fracture, location, and medical approach.