Dominic Stone
The tibia is a large, weight-bearing bone in the lower extremity, connecting the knee and ankle joints. It is the second-largest bone in the human body and is stronger and more prominent than its counterpart, the fibula. The tibia is the site of attachment for many leg muscles, including the sartorius, gracilis, quadriceps femoris, semimembranosus, semitendinosus, and popliteus muscles. The tibialis anterior muscle, located along the front of the tibia, is responsible for dorsiflexion of the foot, enabling movements such as lifting the toes towards the shin and aiding in walking and running. The tibia also serves as the origin or insertion site for 11 muscles, allowing for a range of motions at the knee and ankle joints.
| Characteristics | Values |
|---|---|
| Muscle attachments | Sartorius, gracilis, quadriceps femoris, semimembranosus, semitendinosus, popliteus, tibialis anterior, extensor digitorum longus, soleus, tibialis posterior, and flexor digitorum longus |
| Tibial body | Triangular in cross-section with three surfaces (posterior, medial, and lateral) and three borders (anterior, interosseous, and medial) |
| Tibial surface | The posterior surface has a groove for the tibialis posterior muscle. The lateral surface has a fibular notch that serves as an attachment site for the interosseous membrane. The medial surface is a large bony prominence that forms the medial malleolus |
| Tibial borders | The anterior border is the most prominent and is the attachment site for the articular capsule of the ankle joint |
| Tibial joints | Knee joint, ankle joint, proximal tibiofibular joint, distal tibiofibular joint |
| Tibial fractures | Tibial plateau fractures, Pott's fracture |
| Tibial function | The tibia is the second-largest bone in the body and its main function is to bear weight, with the medial aspect bearing most of the load |
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What You'll Learn
Tibialis anterior
The tibia is the site of attachment for many leg muscles. 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 that originate from the tibia include the tibialis anterior, extensor digitorum longus, soleus, tibialis posterior, and flexor digitorum longus.
The tibialis anterior is a fusiform muscle found in the anterior part of the leg. It is easily palpable lateral to the anterior border of the tibia. It is the primary dorsiflexor of the ankle, with the synergistic action of the extensor hallucis longus, extensor digitorum longus, and peroneous tertius. It also contributes to maintaining the medial arch of the foot. The tibialis anterior aids in any activity that requires moving the leg or keeping the leg vertical. It functions to stabilize the ankle as the foot hits the ground during the contact phase of walking (eccentric contraction) and acts later to pull the foot clear of the ground during the swing phase (concentric contraction). It also functions to lock the ankle, as in toe-kicking a ball, when held in an isometric contraction. The movements of the tibialis anterior are dorsiflexion and inversion of the ankle.
The tibialis anterior arises from the upper two-thirds of the lateral surface of the tibia and the adjoining part of the interosseous membrane and deep fascia overlying it. It is inserted into the medial and inferior surface of the medial cuneiform bone and the adjacent portion of the first metatarsal bone. The muscle is innervated by the deep fibular nerve, and recurrent genicular nerve (L4). A deep portion of the muscle is rarely inserted into the talus, or a tendinous slip may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe.
The tibialis anterior is one of the muscles that tend to be inhibited and underactive. This leads to the overactivity of the synergistic muscles, namely the extensor hallucis longus, extensor digitorum longus, and peroneous tertius. People with an inhibited or weak tibialis anterior, for example, those with hemiplegia or Parkinson's, will have an abnormality in their anticipatory postural adjustment (APA) phase during the gait initiation of the affected limb. Excessive physical activity, especially among runners and military personnel, results in repetitive microtrauma of the tibialis anterior, causing pain along the anterior edge of the tibia known as anterior shin splints or anterior tibial stress syndrome.
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Extensor digitorum longus
The tibia is a large, weight-bearing bone in the lower extremity, connecting the knee and ankle joints. It is the second-largest bone in the body and its primary function is to accept and distribute weight across the knee and to the ankle. The tibia is the site of attachment for many leg muscles, including the extensor digitorum longus.
The extensor digitorum longus is a pennate muscle, situated at the lateral part of the front of the leg. It is one of four muscles in the anterior compartment of the lower leg, alongside the tibialis anterior, extensor hallucis longus, and peroneus (fibularis) tertius. The extensor digitorum longus is the most lateral muscle in the anterior compartment.
The extensor digitorum longus originates from the inferior part of the lateral tibial condyle, the proximal half of the medial surface of the fibula, and the anterior surface of the interosseus membrane. The muscle then descends inferiorly and, just above the ankle, gives off a tendon that passes under the superior extensor retinaculum and through the inferior extensor retinaculum. The extensor digitorum longus is classified as an unipennate muscle because all the muscle fibres attach to one side of the tendon. Within the inferior extensor retinaculum, the tendon splits into four smaller tendons that are wrapped together in a synovial sheath.
The tendons of the extensor digitorum longus course superficially to the extensor digitorum brevis muscle in the dorsum of the foot. The muscle is innervated by the deep fibular nerve (L5, S1), a branch of the common fibular nerve. The leg portion of the muscle is supplied by two arteries: the proximal part by the anterior tibial artery and the distal part by the fibular artery. The tendons of the muscle are vascularized by the anterior lateral malleolar, lateral tarsal, metatarsal, plantar, and digital arteries.
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Soleus
The tibia is a long bone in the lower extremity, connecting the knee and ankle joints. It is the second-largest bone in the body and its main function is to bear weight. The tibia is the site of attachment for many leg muscles.
The soleus is a powerful lower limb muscle in the back part of the lower leg (the calf). It is situated deep to the gastrocnemius muscle, and together they form the calf muscle or triceps surae. The soleus is the most effective muscle for plantar flexion in a bent-knee position. The soleus is innervated by the tibial nerve.
The soleus is a complex, multi-pennate muscle in humans, with a separate (posterior) aponeurosis from the gastrocnemius muscle. Most soleus muscle fibres originate from each side of the anterior aponeurosis, attaching to the tibia and fibula. The soleus is a wide and flat muscle that sits slightly deeper than the gastrocnemius.
The soleus is a vital postural muscle, designed to stop the body from falling forwards at the ankle during a stance. It is also important for maintaining a standing posture; without its constant pull, the body would fall forward. In the seated calf raise, the soleus is the muscle that bears almost all the load.
The soleus is a powerful plantarflexor, along with the other calf muscles. It is important for walking, running, and jumping.
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Tibialis posterior
The tibia is a large, weight-bearing bone in the lower extremity, connecting the knee and ankle joints. The tibia is the site of attachment for many leg muscles. The tibialis posterior is a muscle located deep in the posterior compartment of the lower leg. It is the most central and deepest muscle in the posterior compartment of the leg. It is situated between the flexor digitorum longus and the flexor hallucis longus. The tibialis posterior is attached between the bones of the leg and the foot.
The muscle consists of two parts near its origin: medial and lateral. The medial portion arises from the upper two-thirds of the posterior surface of the tibia, below the soleal line, and from the posterior surface of the interosseous membrane of the leg. The lateral part originates from the upper two-thirds of the posterior surface of the fibula. The two parts become one muscle, which travels towards the foot. At the ankle, the tendon of the tibialis posterior passes posteriorly to the medial malleolus of the tibia. It continues into the medial part of the foot by passing through the tarsal tunnel, deep to the flexor retinaculum of the ankle.
The tibialis posterior is a key stabilising muscle supporting the medial arch of the foot. It also plays an important role in stabilising the medial longitudinal arch. Tibialis posterior dysfunction can lead to flat feet and weak arch control in adults. The tibialis posterior is also related to some important neurovascular structures. For example, it lies anterior to the posterior tibial artery, which gives off a branch called the fibular artery. The anterior tibial artery travels between the medial and lateral parts of the muscle, close to its origin points.
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Flexor digitorum longus
The tibia is a large long bone in the lower extremity, connecting the knee and ankle joints. It is the second-largest bone in the body and plays a crucial role in weight-bearing. The tibia is the site of attachment for many leg muscles, including the flexor digitorum longus.
The flexor digitorum longus (FDL) is a thin muscle that is part of the deep muscle group of the posterior compartment of the lower leg. It originates from the medial part of the posterior surface of the tibia, below the soleal line, and is connected to the fibula by a broad tendon. The muscle fibres descend through the medial aspect of the posterior compartment of the leg. The FDL is innervated by branches of the tibial nerve, which is a branch of the sciatic nerve.
As the muscle fibres travel down the leg, they receive functional support from the quadratus plantae muscle. The quadratus plantae is a two-headed muscle located in the sole of the foot. The two muscle bellies of the quadratus plantae attach to the inserting tendons of the FDL, providing stability and strength to the muscle, especially during toe flexion.
The FDL tendon runs posteriorly to the medial malleolus and deep to the flexor retinaculum, entering the plantar compartment of the foot. In the plantar compartment, the tendon divides into four smaller tendons that insert into the bases of the distal phalanges of the lateral four digits. These tendons are responsible for the movement and curling of the second, third, fourth, and fifth toes, allowing the toes to grip the surface and aiding in balance.
The FDL also functions in the propulsion phase of walking, running, or jumping by pulling the toes downwards towards the ground to attain maximum grip and thrust during toe-off. Additionally, the FDL assists in plantarflexion at the ankle joint and foot inversion at the subtalar joint due to its attachments and course around the medial malleolus.
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Frequently asked questions
The tibia is a large, weight-bearing bone in the lower extremity, connecting the knee and ankle joints. It is the second-largest bone in the body.
The muscles inserted on the tibia are the sartorius, gracilis, quadriceps femoris, semimembranosus, semitendinosus, and popliteus muscles.
The muscles that originate from the tibia are the tibialis anterior, extensor digitorum longus, soleus, tibialis posterior, and flexor digitorum longus muscles.
The tibialis anterior muscle is situated along the front of the tibia. It enables dorsiflexion of the foot, lifting the toes towards the shin.
The extensor digitorum longus muscle runs along the front of the lower leg and extends the toes, aiding in actions such as walking and running.
