Tibia

Proximal part

The proximal end of the tibia features several important landmarks which function as sites of muscle attachment and articular surfaces: two tibial condyles (medial and lateral) separated by intercondylar areas (anterior and posterior). 

The superior surface of the medial condyle is round in shape and somewhat concave, so it fits perfectly into a joint with the medial condyle of the femur. The medial meniscus is sandwiched between the tibia and femur in this joint with attachments to all margins except for the lateral margin. Instead, the lateral margin extends to the medial intercondylar tubercle.

On the other hand, the superior surface of the lateral condyle is pretty much a mirror image of the medial condyle. It is round in shape, somewhat convex, and articulates with the lateral condyle of the femur. The lateral meniscus attaches to all of its margins except for the medial margin. The medial margin extends to the lateral intercondylar tubercle. Note that the lateral and medial menisci are the pads of fibrocartilage inserted to ease the pressure that is transmitted from the femur to the condyles.

The superior surfaces of the condyles are flattened and together they form the superior articular surface called the tibial plateau. Here, the tibial condyles articulate with the femoral condyles within the knee joint. The articular surfaces are separated by two small prominences, the medial and lateral intercondylar tubercles. These tubercles form the intercondylar eminence, which is bordered by the anterior and posterior intercondylar areas.

• The anterior intercondylar area features attachment sites for many structures. Anterior to posterior they are: the anterior horn of the medial meniscus, the anterior cruciate ligament, and the anterior horn of the lateral meniscus. 
• The posterior intercondylar area also has facets for structures to attach. Anterior to posterior these are: the posterior horn of the lateral meniscus, the posterior horn of the medial meniscus, and the posterior cruciate ligament.

On the lateral surface of the proximal end of the tibia just inferior to the lateral condyle is the bony prominence called the tubercle of iliotibial tract or Gerdy’s tubercle. Inferior and lateral to it is the articular facet for the head of the fibula where the tibia and fibula articulate via the superior/proximal tibiofibular joint.

At the anterior surface of the proximal end is the tibial tuberosity. It is an attachment site for the patellar ligament and you can easily spot and palpate this prominence just below your knee. Inferiorly, the tibial tuberosity is continuous with the anterior border of the tibia.

Body

The tibial body (or shaft) is triangular in cross-section and so it has three surfaces (posterior, medial, and lateral) and three borders (anterior, interosseous, and medial).

The medial surface, commonly called the shin, is bound by the anterior and medial borders. It is subcutaneous, meaning that there is only a little fat between the bone and the skin and it has no muscles attachments along most of it. Because of this, the medial surface is palpable along the entire length of the anteromedial aspect of the leg. The lateral surface is bound by the anterior and interosseous margins and is covered by the muscles of the anterior leg compartment. The posterior surface is bound by the interosseous and medial margins and features the soleal line crossing this surface diagonally.

Of the three borders, the anterior border is the most prominent. It can be seen as a distinct margin that begins at the tibial tuberosity and descends all the way to the distal part of the bone. The interosseous border begins inferior to the tubercle of the iliotibial tract and descends down the lateral surface of the tibia. This border connects to the interosseous border of the fibula by the interosseous membrane. At the inferior end of the tibia, the interosseous border is replaced with the fibular notch in which the distal end of the fibula fits. The medial border is most prominent on the medial aspect of the middle third of the of tibia.

Tibia is only one of the many bones making up the human body. Do you know the rest? Test yourself and learn them very fast using active recall and Kenhub's skeletal system quizzes!

Distal part

At the distal end of the tibia, the bone has changed shaped from triangular in cross section to rectangular in cross section. 

• The medial surface of the distal end features a bony extension called the medial malleolus. It articulates with the talus within the ankle joint. 
• The posterior surface shows a vertical groove which is a passage for the tendon of the tibialis posterior muscle. 
• The lateral surface and interosseous border of the distal end provides a facet for the distal end of fibula, called the fibular notch. The tibia and fibula are bound together at this spot by a thickening of interosseous membrane in the inferior/distal tibiofibular joint.
• The anterior surface is smooth and covered by the tendons of the extensor leg muscles. Its lower margin features a rough depression for the attachment of the articular capsule of the ankle joint.

For more anatomical details about the tibia, take a look at the study unit provided below:

Joints

Two major joint in which the tibia takes part are the knee joint and the ankle joint. The tibia also has additional articulations with the fibula where it is anchored to the fibula by the superior, middle, and inferior tibiofibular joints.

The knee joint is certainly something that deserves special attention. Its articular surfaces are the superior surfaces of lateral and medial condyles of the tibia, and the inferior surfaces of the lateral and medial condyles of the femur. At the distal end of the tibia is another major joint: the ankle joint. Here, the talus of the foot articulates with the distal ends of the tibia and fibula.

The tibia also has three articulations with the fibula. The superior/proximal tibiofibular joint is where the proximal end of tibia articulates with the head of the fibula. The articulation site on the tibia is found on the lateral side of its proximal part, while the fibula participates with the medial surface of its head. This joint is reinforced by the anterior and posterior ligaments of fibular head.

The middle tibiofibular joint is the interosseous membrane which spans between the bodies of the tibia and fibula, attaching to the interosseous margins of each bone. It is a sheet of fibrous tissue that joins the tibia and fibula in the tibiofibular syndesmosis.

The inferior/distal tibiofibular joint is formed by the fibular notch of the distal end of the tibia and triangular area of the distal end of the fibula. These articulation surfaces are anchored by extensions of the superior interosseous membrane, while the entire joint is supported by the anterior and posterior tibiofibular ligaments. All three of the tibiofibular joints join the two leg bones together.

Muscle attachments

The tibia is the site of attachment for many leg muscles. Roughly speaking, the lateral surface of the tibia provides attachment sites for the muscles of the anterior compartment of the leg, while the posterior surface provides attachment sites for the muscles of the posterior leg compartment. The muscles of the lateral leg compartment attach to the fibula.

Muscles that insert onto the tibia are the: sartorius, gracilis, quadriceps femoris, semimembranosus, semitendinosus, and popliteus muscles.

Muscles that originate from the tibia are the: tibialis anterior, extensor digitorum longus, soleus, tibialis posterior, and flexor digitorum longus muscles.