The tibia (also known as shinbone, latin: (os) tibia) is the larger and stronger of the two leg bones located medially next to the fibula. The tibia connects the knee with the ankle bones, and participates in forming four joints: the knee, ankle, superior and inferior tibiofibular joint.
As a long bone the tibia is composed of three parts: a diaphysis or shaft, and two epiphyses or extremities: proximal and distal.
Proximal epiphysis of tibia
The proximal epiphysis is the upper extremity of the tibia, and it features the following landmarks:
- medial condyle,
- lateral condyle,
- intercondylar area,
- intercondylar eminence,
- anterior intercondylar area,
- posterior intercondylar area,
- superior articular surface,
- fibular articular surface.
The medial condyle of the tibia is the medial expansion and the lateral condyle is the lateral expansion at the proximal end of the tibia. The medial and lateral condyles of the tibia are separated by the intercondylar area, which is separated into anterior and posterior intercondylar areas by the intercondylar eminence.
The intercondylar eminence is a bony elevation between the articular surfaces of the tibia, for attachment of the cruciate ligaments and menisci.
The anterior intercondylar area is the area between the knee joint surfaces of the tibia and in front of the intercondylar eminence, while the posterior intercondylar area is located between the articular surfaces behind the intercondylar eminence.
There are two articular surfaces on the proximal epiphysis of the tibia.
The superior articular surface is the tibial articular surface of the knee joint.
The fibular articular surface is the articular facet for the head of the fibula on posterolateral aspect of the lateral condyle of the tibia.
Diaphysis of tibia
The diaphysis or shaft of the tibia is triangular in cross-sections and has three borders:
- anterior margin, featuring
- tibial tuberosity,
- interosseous margin,
- medial margin.
The anterior margin of the tibia is directed anteriorly, the medial margin or the inner margin is facing medially, and the interosseous margin of the tibia is facing the fibula and providing the attachment to the interosseous membrane along most of its margin.
The tibial tuberosity is the rough-ended area on the upper end of the anterior margin of the tibia. The tibial tuberosity is the attachment site of the patellar ligament.
The shaft of the tibia forms three surfaces:
- medial surface,
- lateral surface,
- posterior surface, featuring
- soleal line.
The medial surface of the tibia is directed anteromedially, the lateral surface is facing anterolaterally, and the posterior surface is directed posteriorly.
The soleal line of the tibia is a line extending obliquely from the upper, lateral part of the shaft of the tibia, downward and across to the medial side, for attachment of the soleus muscle.
Distal epiphysis of tibia
The distal epiphysis is the lower extremity of the tibia, and it presents:
- medial malleolus, with
- malleolar articular surface,
- malleolar groove,
- fibular notch,
- inferior articular surface.
A malleolus refers to a bony prominence on each side of the ankle. The medial malleolus is the prominence on the inner side of the ankle, specifically, on the distal epiphysis of the tibia.
The malleolar articular surface is the lateral articular surface of the medial malleolus facing the talus.
The malleolar groove is a small groove on the posterior aspect of the medial malleolus for attachment of the tendon of the tibialis posterior muscle.
The fibular notch is a depression on the lateral surface of the distal epiphysis of the tibia, which articulates with the fibula.
The inferior articular surface is the inferior joint surface of the tibia facing the talus.