Leg Flashcards
What are the muscles in the anterior compartment of the leg?
There are four muscles in the anterior compartment of the leg; tibialis anterior, extensor digitorum longus, extensor hallucis longus and fibularis tertius.
Collectively, they act to dorsiflex and invert the foot at the ankle joint. The extensor digitorum longus and extensor hallucis longus also extend the toes.
The muscles in this compartment are innervated by the deep fibular nerve (L4-L5), and blood is supplied via the anterior tibial artery.
Give the attachments, innervation and action of Tibialis Anterior
The tibialis anterior muscle is located alongside the lateral surface of the tibia.
It is the strongest dorsiflexor of the foot.
To test the power of the tibialis anterior, the patient can be asked to stand on their heels.
Attachments: Originates from the lateral surface of the tibia, attaches to the medial cuneiform and the base of metatarsal I.
Actions: Dorsiflexion and inversion of the foot.
Innervation: Deep fibular nerve.
Give the attachments, innervation and action of Extensor Digitorum Longus
The extensor digitorum longus lies lateral and deep to the tibialis anterior. The tendons of the EDL can be palpated on the dorsal surface of the foot.
Attachments: Originates from the lateral condyle of the tibia and the medial surface of the fibula. The fibres converge into a tendon, which travels to the dorsal surface of the foot. The tendon splits into four, each inserting onto a toe.
Actions: Extension of the lateral four toes, and dorsiflexion of the foot.
Innervation: Deep fibular nerve.
Give the attachments, innervation and action of Extensor Hallucis Longus
The extensor hallucis longus is located deep to the EDL and TA.
Attachments: Originates from the medial surface of the fibular shaft. The tendon crosses anterior to the ankle joint and attaches to the base of the distal phalanx of the great toe.
Action: Extension of the great toe and dorsiflexion of the foot.
Innervation: Deep fibular nerve.
Give the attachments, innervation and action of Fibularis Tertius
The fibularis tertius muscles arises from the most inferior part of the EDL. It is not present in all individuals, and is considered by some texts as a part of the extensor digitorum longus.
Attachments: Originates with the extensor digitorum longus from the medial surface of the fibula. The tendon descends with the EDL, until they reach the dorsal surface of the foot. The fibularis tertius tendon then diverges and attaches to metatarsal V.
Actions: Eversion and dorsiflexion of the foot.
Innervation: Deep fibular nerve.
What are the muscles in the lateral compartment of the leg?
There are two muscles in the lateral compartment of the leg; the fibularis longus and brevis. In older texts, they are referred to as the peroneal longus and brevis. As the fibularis longus and brevis are in the same muscular compartment, they have the same function and innervation.
The common anatomical function of the muscles is eversion – turning the sole of the foot outwards. You’ll notice that from the anatomical position, only a few degrees of eversion is possible. In reality, the job of these muscles is to fix the medial margin of the foot during running, and preventing excessive inversion.
Give the attachments, innervation and actions of Fibularis Brevis
Attachments: It originates from the inferior and lateral surface of the fibular shaft. The muscle belly forms a tendon, which descends with the fibularis longus tendon. It travels into the foot, posterior to the lateral malleolus, passing over the calcaneus and the cuboidal bones. The tendon of the fibularis brevis attaches to a tubercle on metatarsal V.
Actions: Eversion of the foot.
Innervation: Superficial fibular (peroneal) nerve, L4-S1.
Give the attachments, innervation and actions of Fibularis Longus
Attachments: The tendon of the fibularis longus has a slightly odd anatomical course:
The fibularis longus originates from the superior and lateral surface of the fibula and the lateral tibial condyle.
The fibres converge into a tendon, which the descends into the foot, posterior to the lateral malleolus.
The tendon then crosses under the foot, and attaches to the bones on the medial side, namely the medial cuneiform and base of metatarsal I.
Actions: Eversion and plantarflexion of the foot. Also supports the lateral and tranverse arches of the foot.
Innervation: Superficial fibular (peroneal) nerve, L4-S1.
Describe the relevance of the calcaneal tendon
The superficial muscles form the characteristic ‘calf’ shape of the posterior leg. They all insert into the calcaneus of the foot (the heel bone), via the calcaneal tendon. The calcaneal reflex tests spinal roots S1-S2.
To minimise friction during movement, there are two bursae (fluid filled sacs) associated with the calcaneal tendon:
Subcutaneous calcaneal bursa – lies between the skin and the calcaneal tendon.
Deep bursa of the calcaneal tendon – lies between the tendon and the calcaneus.
Give the attachments, innervation and action of Gastrocnemius
The gastrocnemius is the most superficial of all the muscles in the posterior leg.
It has two heads – medial and lateral, which converge to form a single muscle belly.
The muscle is comprise of mainly fast twitch muscle fibres, which produce forceful movements such as running and jumping.
Attachments: The lateral head originates from the lateral femoral condyle, and medial from the medial condyle. The fibres converge, and form a single muscle belly. In the lower part of the leg, the muscle belly combines with the soleus to from the calcaneal tendon, with inserts onto the calcaneus (the heel bone).
Actions: It plantarflexes at the ankle joint, and because it crosses the knee, it is a flexor there.
Innervation: Tibial nerve.
Give the attachments, innervation and action of Plantaris
The plantaris is a small muscle with a long tendon, which can be mistaken for a nerve as it descends down the leg. It is absent in 10% of people.
Attachments: Originates from the lateral supracondylar line of the femur. The muscle descends medially, condensing into a tendon that runs down the leg, between the gastrocnemius and soleus. The tendon blends with the calcaneal tendon.
Actions: It plantarflexes at the ankle joint, and because it crosses the knee, it is a flexor there. It is not a vital muscle for these movements.
Innervation: Tibial nerve.
Give the attachments, innervation and action of Soleus
The soleus is located deep to the gastrocnemius. It is large and flat, named soleus due to its resemblance of a sole – a flat fish.
Attachments: Originates from the soleal line of the tibia and proximal fibular area. The muscle narrows in the lower part of the leg, and joins the calcaneal tendon.
Actions: Plantarflexes the foot at the ankle joint.
Innervation: Tibial Nerve.
What are the deep muscles of the posterior leg?
There are four muscles in the deep compartment of the posterior leg. One muscle, the popliteus, acts only on the knee joint. The remaining three muscles (tibialis posterior, flexor hallucis longus and flexor digitorum longus) act on the ankle and foot.
Give the attachments, innervation and action of Popliteus
The popliteus is located superiorly in the leg. It lies behind the knee joint, forming the base of the popliteal fossa.
There is a bursa (fluid filled sac) that lies between the popliteal tendon and the posterior surface of the knee joint. It is called the popliteus bursa.
Attachments: Originates from the posterior surface of the proximal tibia. The fibres pass upwards and laterally, attaching to the lateral condyle of the femur.
Actions: Laterally rotates the femur on the tibia – ‘unlocking’ the knee joint so that flexion can occur.
Innervation: Tibial nerve.
Give the attachments, innervation and action of Tibialis Posterior
The tibialis posterior is the deepest out of the four muscles. It lies between the flexor digitorum longus and the flexor hallucis longus.
Attachments: Originates from the interosseous membrane between the tibia and fibula, and posterior surfaces of the two bones. The tendon enters the foot posterior to the medial malleolus, and attaches to the plantar surfaces of the medial tarsal bones.
Actions: Inverts and plantarflexes the foot, maintains the medial arch of the foot.
Innervation: Tibial nerve.
Give the attachments, innervation and action of
Flexor Digitorum Longus
The FDL is (surprisingly) a smaller muscle than the flexor hallucis longus. It is located medially in the posterior leg.
Attachments: Originates from the medial surface of the tibia, attaches to the plantar surfaces of the lateral four digits.
Actions: Flexes the lateral four toes.
Innervation: Tibial nerve.
Give the attachments, innervation and action of Flexor Hallucis Longus
The flexor hallucis longus muscle is found on the lateral side of leg. This is slightly counter-intuitive, as it is opposite the great toe, which it acts on.
Attachments: Originates from the posterior surface of the fibula, attaches to the plantar surface of the phalanx of the great toe.
Actions: Flexes the great toe.
Innervation: Tibial nerve.
Describe features of the proximal end of the tibia
At the proximal end, the tibia is widened by the medial and lateral condyles, aiding in weight bearing. The condyles form a flat surface, known as the tibial plateau. This structure articulates with the femoral condyles to form the major articulation of the knee joint.
Located between the condyles is a region called the intercondylar eminance – this consists of two tubercles and a roughened area. This area is the main site of attachment for the ligaments and the menisci of the knee joint. The tibial intercondylar tubercles fit into the intercondylar fossa of the femur.
On the anterior surface of the proximal tibia, inferior to the condyles, the tibial tuberosity is situated. This is where the patella ligament attaches
Describe the shaft of the tibia
The shaft of the tibia has three borders and three surfaces; anterior, posterior and lateral.
Anterior border – The start of the anterior border is marked by the tibial tuberosity. It is palpable down the anterior surface of the leg as the shin. Here, the periosteal covering of the tibia is susceptible to damage, presenting clinically as bruising.
Posterior surface – This is marked by a ridge of bone called the soleal line. It runs inferomedially, eventually blending with the medial border of the tibia. It is here where part of the soleus muscle originates
Lateral border – Also known as the interosseous border. This gives attachment to the interosseous membrane that binds the tibia and the fibula together.
Label the posterior surface of the tibia
Describe features of the fibula
As it does not articulate with the femur at the knee joint, its main function is to act as an attachment for muscles, and not as a weight bearer.
At the proximal end, the fibula has a enlarged head, which contains a facet for articulation with the lateral condyle of the tibia. On the posterior and lateral surface of the fibular neck, the common fibular nerve can be found.
The fibular shaft has three surfaces – anterior, lateral and posterior. The leg is split into three compartments, and each surface faces its respective compartment e.g anterior surface faces the anterior compartment of the leg.
Distally, the lateral surface continues inferiorly, and is called the lateral malleolus. The lateral malleolus is more prominent than the medial malleolus, and can be palpated at the ankle on the lateral side of the leg
