Calf Anatomy

The calf is an area at the back of the leg. It brings together two bones and three muscles, which are essential for the movements of the knee, ankle and foot. To learn more about this anatomical part located in the popliteal fossa, read on. You will find all the information related to the biomechanics of the calf and knee.

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Calf parts and anatomy

Bones and joints

• Tibia: This elongated, triangular-shaped bone runs along the anterior part of the calf. It is joined in the upper area, by means of the glenoid cavities, with the femoral condyles, giving rise to the knee joint. On the lower plane, it is connected to the upper aspect of the talus (forming the ankle).
• Fibula: Also known as fibula, it runs along the posterior aspect of the calf, parallel to the tibia. The lower part of the fibula has a malleolus that is joined to the talus and calcaneus by ligaments.
• Proximal or superior tibioperoneal: It is responsible for making small movements between the head of the fibula and the lateral condyle of the tibia.
• Distal tibioperoneal: This is the only syndesmosis-type joint in the leg. It is a membrane-like joint located between the tibia and fibula, thus generating the interosseous ligament.
• Tibioperoneoastotalar: Also known as the tibiotarsal joint. It is a synovial joint and allows movement of the lower part of the tibia and fibula with the talus.

Muscles

• Gastrocnemius or calf: Its function is plantar flexion of the foot. It is a muscle that originates in the femoral condyles and separates into two, always with a route above the soleus. It inserts into the Achilles tendon together with the soleus tendon, so it can be divided into three zones: medial head, lateral head and lower portion.
• Soleus: It is also responsible for plantar flexion. Its origin is multipeniform, it is produced in the membrane of the tibia and fibula, in the simular head and in the medial border of the tibia. It inserts on the soleus tendon to form the Achilles tendon, together with the calf tendon, and on the posterior surface of the calcaneal bone.

Ligaments

• Anterior of the fibular head: It is responsible for joining the lateral condyle of the tibia to the head of the fibula, by means of three wide bands.
• Posterior of the fibular head: Unlike the anterior connective tissue, this ligament is a single band that runs from the head of the fibula to the lateral condyle of the tibia, in the posterior part.
• Interosseous: A tissue located between the tibia and fibula, which works with the distal tibioperoneal joint.
• Anterior peroneoastotalar: originates from the lateral malleolus of the fibula to the neck of the talus.
• Posterior peroneoastotalar: The distal fibular end gives rise to this ligament, which inserts into the talus through its lateral tubercle.
• Peroneocalcaneal: This ligament runs from the apex of the lateral malleolus of the fibula to a tubercle of the calcaneus.

Biomechanics of the leg (calf and knee)

• Extension: This action consists of keeping the leg at rest. That is, it is to place the tibia and fibula in a straight line in relation to the axis of the femur, so the amplitude is 0°.
• Flexion: This is the opposite movement to extension and is performed with an opening of 130°, although it can reach 170° with the help of the hand. It involves bringing the heel to the buttock, causing the cruciate ligaments, menisci and quadriceps to offer resistance.
• External rotation: If the tibia is considered as the axis, this biomechanical action is to bring the distal part of the foot towards the side of the fibula. Its maximum amplitude can reach 90° with a lot of training, as is the case with ballet dancers.
• Internal rotation: It is possible to biomechanically rotate the foot towards the internal axis of the tibia, thanks to the action of the calf, soleus, lateral ligaments and tendons, which prevent the displacement of the tibia with respect to the fibula.
• Plantar flexion: This movement is produced by the action of the gastrocnemius and soleus muscles. It involves placing the tibia at a maximum angle of 90° to the dorsal part of the foot.
• Dorsal flexion: This consists of bringing the toes towards the tibia, forming an angle that does not exceed 30° of opening. This biomechanical movement is carried out by the action of different elements, including the gastrocnemius and soleus.