Tibias

Tibias is the plural form of tibia, the large, weight-bearing bone of the lower leg in humans and many vertebrates. The tibia runs from the knee to the ankle and, together with the fibula, supports body weight and enables locomotion. In humans, the tibia is located medially and bears most of the load transmitted through the leg.

Anatomy: The proximal tibia has the medial and lateral condyles that articulate with the femoral condyles to form the knee joint; the top surface is known as the tibial plateau. The tibial tuberosity serves as the insertion for the patellar ligament. The shaft is triangular in cross-section and composed of cortical bone with a medullary cavity. The distal tibia ends in the medial malleolus, which participates in the ankle mortise together with the fibula.

Function and clinical relevance: The tibias transmit body weight from the femur to the foot and provide sites for muscle attachment, including the quadriceps via the patellar ligament and the calf muscles via the soleus and Achilles tendon. Their length and subcutaneous location in the lower leg make them susceptible to injuries, especially fractures. Common injuries include proximal tibial plateau fractures, tibial shaft fractures, and distal tibial fractures near the ankle. Stress fractures are seen in runners and military recruits. Treatments range from immobilization to surgical fixation such as intramedullary nailing or plating.

Terminology and variation: The word tibial is derived from Latin tibia. While tibias is widely used, tibiae is also correct as the classical plural. In many vertebrates the tibia is a major hind limb bone, with length relative to the fibula varying among species.