MUSCULAR COMPARTMENT OF LEG

Extensor digitorum

Hybrid muscles are the muscles having more than one nerve supply

Pctoralis major: lateral & medial pectoral nerves

Brachialis: additional proprioceptive fibres from radial nerve, in addition to its muscular nerve, musculocutaneous nerve.

 Extensor digitorum is supplied by the posterior interosseous nerve only.

Popliteus

• Locking or screw home mechanism: Conjunct medial rotation of the femur on the tibia in later stages of extension due to quadriceps femoris locks the knee joint.
• Unlocking of the knee joint: At beginning of flexion from the full extension with foot flexed, lateral rotation by Popliteus muscle unlocks the joint.

ORIGIN:

• The tibialis posterior muscle originates on the inner posterior borders of the tibia and fibula.
• It is also attached to the interosseous membrane, which attaches to the tibia and fibula.

INSERTION:

• The tendon of the tibialis posterior muscle (sometimes called the posterior tibial tendon) descends posterior to the medial malleolus and terminates by dividing into plantar, main, and recurrent components.
• The main portion inserts into the tuberosity of the navicular and the plantar surface of the medial cuneiform.
• The plantar portion inserts into the bases of the second, third and fourth metatarsals, the intermediate and lateral cuneiforms and the cuboid.
• The recurrent portion inserts into the sustentaculum tali of the calcaneus.

The peroneus longus and brevis act primarily as evertors, with the peroneus brevis being the stronger of the two. In the question, the evertor inserted to the medial cuneiform, which is peroneus longus.

The peroneus brevis inserts on the base of the fifth metatarsal and the peroneus longus courses under the cuboid to insert on the base of the first metatarsal and medial cuneiform. 

The tibialis anterior is the dorsiflexor of foot at the ankle joint. It is the invertor of the foot at the midtarsal and subtalar joints.

Tibialis posterior is the principal invertor of the foot.

Normal walking constitutes of the stance phase (when at least one leg is in contact with the ground) and swing phase (when the leg is in the air). 

Tibialis posterior is the deepest and most centrally located muscle in the deep posterior compartment of the leg. It arises from the upper posterior aspect of tibia, fibula and interosseous membrane and passes medially deep to the flexor retinaculum. Its tendons flares and inserts into the navicular, tarsal bones, and bases of the second, to fourth metatarsals.

• Tibialis posterior tendon
• Flexor digitorum longus tendon
• Flexor hallucis longus tendon
• Posterior tibial artery
• Tibial nerve.

A. i.e. Biceps femoris; B. i.e. Both heads of gastrocnemius; C. i.e. Adductor magnus

A i.e. Peroneus brevis 

Violent inversion of foot may cause avulsion of tuberosity of 5^n1, metatarsal base, the insertion of peroneus (fibularis) brevis muscleQ.

A i.e. Gastrocnemius C i.e. Plantaris 

A i.e. Extensor digitorum longus; B i.e. Extensor hallucis longus; C i.e. Tibialis anterior

A. i.e. Plantans; B. i.e. FHL; C. i.e. Soleus

A. i.e. Peroneus brevis

Popliteus

Popliteus is a deep muscle of posterior compartment of leg.

Features of popletius are –

Origin

• Lateral surface of lateral condyle of femur, origin is intracapsular.
• Outer margin of lateral meniscus of knee.

Insertion

• Posterior surface of shaft of tibia above soleal line.

Nerve supply

• Tibial nerve

Action

• Ulocks knee joint by lateral rotation of femur on tibia prior flexion.
• Accessory flexor of knee.

 Tibialis anterior

Ans. is ‘c’ i.e., Inversion of foot

Ans. is ‘b’ i.e., Lateral rotation of femur

Ponliteus

* Popliteus is a deep muscle of posterior compartment of leg.

* Features of popletius are ‑

Origin

* Lateral surface of lateral condyle of femur, origin is intracapsular.

* Outer margin of lateral meniscus of knee.

Insertion

* Posterior surface of shaft of tibia above soleal line.

Nerve supply

* Tibial nerve

Action

* Ulocks knee joint by lateral rotation of femur on tibia prior flexion.

* Accessory flexor of knee

Ans. is ‘b’ i.e., Soleus

Soleus is known as ‘peripheral heart’ as it helps in venous return from lower limb.

 Ans:A. Tibialis Anterior.

Inversion of foot is shown in the image.