Tibia
The tibia (tibia) is the main weight-bearing structure of the leg. It consists of a proximal epiphysis, a diaphysis (shaft), and a distal epiphysis.
On the proximal epiphysis is the superior articular surface (facies articularis superior), which is divided into two large condyles: medial (condylus medialis) and lateral (condylus lateralis). Between them lies the intercondylar eminence (eminentia intercondylaris). It is formed by two tubercles (medial and lateral), with the anterior and posterior intercondylar areas lying anterior and posterior to it. On the inferoposterior side of the lateral condyle, there is a fibular articular surface for articulation with the head of the adjacent bone.
The shaft of the tibia (corpus tibiae) has a triangular cross-section. It features three surfaces (medial, lateral, and posterior) and three borders:
- The anterior border (margo anterior) is the sharpest, easily palpable under the skin, and superiorly transitions into the tibial tuberosity (tuberositas tibiae), to which the patellar ligament attaches.
- The medial border (margo medialis).
- The interosseous border (margo interosseus) faces laterally toward the interosseous membrane.
On the posterior surface of the shaft (facies posterior), the soleal line (linea m. solei) runs in an arch from the interosseous to the medial border.
The distal epiphysis extends on its inner side into a large process — the medial malleolus (malleolus medialis). On its outer side is an articular surface for articulation with the talus. On the lateral side of the epiphysis is the fibular notch (incisura fibularis), and inferiorly lies the inferior articular surface.
Fibula
The fibula (fibula) is a slender bone located lateral to the tibia. It also has a shaft and two ends.
Its proximal epiphysis is represented by the head (caput fibulae), which terminates superiorly in a pointed apex (apex capitis fibulae). On the inner side of the head is an articular surface for articulation with the lateral condyle of the tibia. The region immediately below the head is called the neck (collum fibulae).
The shaft of the fibula (corpus fibulae) has three surfaces (lateral, medial, posterior) and three borders. The anterior border is the sharpest. The posterior border is rounded. The interosseous border is less pronounced, descending from the head and merging in the lower third with the well-defined medial crest (crista medialis), which runs from back to front.
The distal epiphysis forms the lateral malleolus (malleolus lateralis), which is easily palpable subcutaneously on the outer aspect of the leg. On its inner side is an articular surface for the talus, and on its posterior surface is a characteristic depression — the malleolar fossa (fossa malleoli lateralis).
How to distinguish bones and determine their side
During practical classes, it is important to quickly identify whether a bone is left or right and which bone you are holding.
For the tibia:
- The sharp anterior border and tuberosity must face forward.
- The medial malleolus at the lower end points inward (medially).
- The soleal line is located posteriorly.
For the fibula:
- The rounded head is superior (proximal), and the elongated malleolus is inferior (distal).
- The articular surfaces on both ends face inward (toward the tibia and talus).
- The sharp border of the shaft faces forward, and the malleolar fossa is located posteriorly.
| Sign | Tibia | Fibula |
|---|---|---|
| Position | Medial | Lateral |
| Main load | Bears body weight | Bears almost none |
| Key prominences | Tuberositas tibiae, linea m. solei, medial malleolus | Head with apex, neck, lateral malleolus, fossa malleoli lateralis |
| Interosseous border | Located laterally | Weakly pronounced, merges with crista medialis |
Briefly: answers to topical questions
Which bones does the tibia articulate with?
The tibia articulates with three bones: the femur, the fibula, and the talus.
- The femur (femur) — articulates with the superior articular surface of the tibia, participating in the formation of the knee joint.
- The fibula (fibula) — articulates with the fibular articular facet on the lateral condyle proximally and at the fibular notch distally.
- The talus (talus) — articulates with the inferior articular surface and the articular surface of the medial malleolus, forming the ankle joint.
Which muscles originate from or attach to the fibula?
The fibula is the origin of the peroneus longus (m. peroneus longus / m. fibularis longus): from the head and upper part of the lateral surface of the fibula. Other specific muscles originating from the fibula are not named in sources; it is only noted that it serves as a stroma for muscle attachments.
Which ligaments attach to the anterior and posterior intercondylar areas of the tibia?
The cruciate ligaments, which ensure knee joint stability, attach to the intercondylar areas of the tibia.
- The anterior cruciate ligament (lig. cruciatum anterius) — connects the lateral condyle of the femur to the anterior intercondylar area of the tibia.
- The posterior cruciate ligament (lig. cruciatum posterius) — fixes to the posterior intercondylar area of the tibia.
Where is the malleolar fossa located and which ligament does it serve to attach?
The malleolar fossa (fossa malleoli lateralis) is located on the posterior surface of the lateral malleolus of the distal epiphysis of the fibula. The provided materials do not specify which exact ligament attaches to this fossa, but note that it serves as an important landmark for determining the side of the bone.
Which tendons pass through the malleolar sulcus on the posterior surface of the medial malleolus?
The tendons of three leg muscles pass through the malleolar sulcus (sulcus malleolaris medialis) behind the medial malleolus. From anterior to posterior within the malleolar canal are:
- Tendons of the tibialis posterior (m. tibialis posterior);
- Tendon of the flexor digitorum longus (m. flexor digitorum longus);
- Tendon of the flexor hallucis longus (m. flexor hallucis longus).
Mnemonic for placement: "Thick Tibia" — massive bone, lies internally (medially). "Filigree Fibula" — slender bone, lies externally (laterally).
Class and exam questions
Does the fibula bear body weight?
Virtually none. The main axial load during standing and walking is transmitted through the massive tibia. The fibula is primarily needed for muscle attachment and forming the lateral part of the ankle joint.
Where is the soleus line located?
It is located on the posterior surface of the body of the tibia, slightly below the proximal epiphysis, and runs in an arc from the interosseous border to the medial border.
How to quickly find the intercondylar eminence?
You should look for it on the proximal epiphysis of the tibia, right on the superior articular surface between the medial and lateral condyles.
What else to study on this topic
- The intercondylar areas (area intercondylaris anterior et posterior) and their role in the attachment of the cruciate ligaments of the knee.
- The articular surfaces of the malleoli and the mechanism of ankle joint formation.
- Topography of the surfaces and borders of the fibular diaphysis.
- Detailed structure of the medial crest (crista medialis) on the fibula.
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