Tibia anatomy: the shinbone and main weight-bearing bone of the leg

Also called

Shinbone

What it is

The shinbone, the medial and main weight-bearing bone of the leg.

Location

Lies between the knee (articulating with the femur) and the ankle (articulating with the talus), and joins the fibula at the tibiofibular joints.

Function

Transmits body weight from the femur to the foot.

Body system

Skeletal · paired (left and right)

FMA ID

FMA24478 (Foundational Model of Anatomy)

Key facts

• Features the tibial tuberosity, anterior border (shin) and medial malleolus.
• Its proximal end forms the medial and lateral condyles (tibial plateau); the patellar ligament inserts on the tibial tuberosity.
• The soleal line on its posterior surface gives origin to soleus.

Clinical relevance

Its subcutaneous surface makes open fractures common.

The tibia lies on the medial (big-toe) side of the leg, between the knee above and the ankle below. It is the weight-bearing bone of the leg; the fibula beside it does not carry body weight. Its anterior border and its medial surface sit directly under the skin, so you can feel the bone along the whole front and inner side of the shin. (OpenStax Anatomy and Physiology 2e, 8.4: Bones of the Lower Limb.)

The two bones of the lower leg, the tibia and fibula, are tied together by the interosseous membrane, a sheet of dense connective tissue attached to the interosseous border on the lateral side of the tibial shaft. People often say "bones in the lower leg" for this pair; in anatomical language "leg" means only the segment from knee to ankle, and the thigh bone (femur) is a separate segment. (OpenStax Anatomy and Physiology 2e, 8.4: Bones of the Lower Limb.)

The proximal tibia is widened by the medial and lateral condyles. Their flat upper surfaces form the tibial plateau, which articulates with the condyles of the femur at the knee joint. Between the two condyles the intercondylar eminence rises as the medial and lateral intercondylar tubercles. (TeachMeAnatomy: The Tibia.)

In front of and behind the eminence are the anterior and posterior intercondylar areas, where the knee's internal structures attach. From front to back, the anterior area receives the anterior horn of the medial meniscus, the anterior cruciate ligament and the anterior horn of the lateral meniscus; the posterior area receives the posterior horn of the lateral meniscus, the posterior horn of the medial meniscus and the posterior cruciate ligament. (Kenhub: Tibia.)

On the lateral surface just below the lateral condyle is Gerdy's tubercle (the tubercle of the iliotibial tract), where the iliotibial band attaches. Below and behind it, on the underside of the lateral condyle, is the fibular articular facet for the head of the fibula. On the front of the bone, the tibial tuberosity receives the patellar ligament (patellar tendon) and continues downwards as the anterior border. (Kenhub: Tibia.)

The shaft (body) is triangular in cross-section, with three surfaces (medial, lateral and posterior) and three borders (anterior, interosseous and medial). The anterior border is the sharp ridge of the shin. The medial surface is covered only by skin and has few muscle attachments. The lateral surface is covered by the muscles of the anterior compartment, and the interosseous border anchors the interosseous membrane. (Kenhub: Tibia.)

On the posterior surface, the soleal line runs diagonally downwards and medially and gives origin to part of soleus. Popliteus attaches above this line, while flexor digitorum longus and tibialis posterior arise from the posterior surface below it. (TeachMeAnatomy: The Tibia.)

Several thigh muscles insert on the proximal tibia. Sartorius, gracilis and semitendinosus insert together on the upper medial surface through a shared tendon arrangement called the pes anserinus, semimembranosus inserts on the medial condyle, and quadriceps femoris acts on the tibial tuberosity through the patellar ligament. Tibialis anterior arises from the lateral surface and the interosseous membrane. (Kenhub: Tibia.)

Towards the ankle the shaft changes from triangular to roughly rectangular in cross-section. On its medial side the distal tibia projects downwards as the medial malleolus, the bony bump on the inner side of your ankle, which articulates with the talus as part of the ankle joint. A vertical groove on the back of the distal tibia carries the tendon of tibialis posterior. (Kenhub: Tibia.)

On the lateral side of the distal tibia is the fibular notch, a hollow that holds the lower end of the fibula and forms the distal tibiofibular joint. The front of the distal tibia is smooth and is crossed by the extensor tendons on their way to the foot. (Kenhub: Tibia.)

Behind the medial malleolus, the flexor retinaculum stretches to the calcaneus and roofs over the tarsal tunnel. From front to back the tunnel carries the tibialis posterior tendon, the flexor digitorum longus tendon, the posterior tibial artery and vein, the tibial nerve and the flexor hallucis longus tendon, remembered as "Tom, Dick and a Very Nervous Harry". (TeachMeAnatomy: The Tarsal Tunnel.)

The tibia takes part in five joints. Above, its condyles form the knee joint with the femur. Below, the distal tibia and medial malleolus form the ankle (talocrural) joint with the talus. With the fibula it forms the superior tibiofibular joint (a plane synovial joint at the fibular head), the middle tibiofibular joint (the interosseous membrane between the shafts) and the inferior tibiofibular joint (a fibrous syndesmosis at the fibular notch). (Kenhub: Tibiofibular joints.)

The inferior tibiofibular joint is held by the anterior and posterior tibiofibular ligaments and a strong interosseous ligament. When the ankle dorsiflexes, the fibula glides upwards and rotates slightly at this joint, widening the space between the two bones a little to accommodate the talus. (Kenhub: Tibiofibular joints.)

The tibia ossifies from a primary centre in the shaft and secondary centres at each end. In the classic table of Keibel and Mall, the shaft centre appears around the 44th day of embryonic life, the proximal epiphysis around birth and the distal epiphysis in the second year. An occasional separate centre for the tibial tuberosity appears around the 13th year and fuses first with the proximal epiphysis. The fusion ages in that table (roughly the 16th to 24th years) come from early 20th-century observers and vary between people. (UNSW Embryology: Lower limb ossification table.)

The growing tibial tuberosity is the site of Osgood-Schlatter disease, an apophysitis where the patellar tendon inserts. It typically affects children in the second decade, about 10 to 15 years in boys and 8 to 12 in girls, is bilateral in 20 to 30 percent of cases and usually settles when growth ends. (Vaishya et al. Apophysitis of the Tibial Tuberosity (Osgood-Schlatter Disease): A Review. Cureus 2016.)

The tibia is the medial, thicker bone and carries body weight from the knee to the ankle. The fibula is the slender lateral bone; it does not bear weight and serves mainly for muscle attachment, and only its two ends can be felt. The tibia's distal projection is the medial malleolus, while the fibula ends as the lateral malleolus on the outer side of the ankle. (OpenStax Anatomy and Physiology 2e, 8.4: Bones of the Lower Limb.)

The tibia is the most frequently fractured long bone, and the shaft is its most vulnerable part. Because the medial surface lies under the skin, open fractures, where bone breaks through the skin, are common and carry a high risk of infection. Shaft fractures usually follow high-energy trauma such as road traffic collisions or falls from a height. (Kenhub: Tibia.)

Shaft fractures are often accompanied by a fibular fracture. Fractures of the proximal tibia (tibial plateau fractures) can involve the condyles and injure the menisci and knee ligaments; they are graded with the Schatzker classification, and doctors watch closely for compartment syndrome before and after surgery. (TeachMeAnatomy: The Tibia.)

A medial malleolus fracture can occur when the foot is forced into inversion and the talus is driven against the malleolus. It rarely occurs alone: the lateral malleolus is often broken as well, which makes the ankle unstable and usually needs surgery. (TeachMeAnatomy: The Tibia.)

The flat anteromedial surface of the proximal tibia, 2 to 3 cm below the tibial tuberosity, is a standard site for emergency intraosseous access, where fluids and drugs are given into the bone marrow when a vein cannot be found. (TeachMeAnatomy: The Tibia.)

Medial tibial stress syndrome ("shin splints") is an overuse condition felt as a dull ache along the posteromedial border of the tibia, most often in its middle and distal thirds. It is common in runners, dancers and military recruits and has to be told apart from a tibial stress fracture, which tends to give more localised pain and tenderness. (Bhusari & Deshmukh. Shin Splint: A Review. Cureus 2023.)

Run a finger down the front of your shin: the sharp ridge is the anterior border, and the flat area on its inner side is the medial surface. Just below the kneecap you can feel the tibial tuberosity, where the patellar ligament ends, and at the ankle the rounded medial malleolus forms the inner ankle bump. (OpenStax Anatomy and Physiology 2e, 8.4: Bones of the Lower Limb.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Plantaris · muscular
• Interosseous membrane of leg · skeletal
• Soleus · muscular
• Anterior tibial artery · cardiovascular
• Small saphenous vein · cardiovascular
• Tibialis posterior · muscular
• Fibula · skeletal
• Anterior tibial vein · cardiovascular
• Tibialis anterior · muscular
• Fibularis longus · muscular