Corpus: Lower leg muscles
Synonym: calf muscles
1. Definition
The lower leg muscles are a group of skeletal muscles located in the lower leg.
2. Arrangement
The lower leg muscles are organized into three compartments, separated by fascia, the interosseous membrane, and intermuscular septa:
- Anterior compartment: Contains the extensor muscles, innervated by the deep fibular nerve.
- Posterior compartment: Contains the flexor muscles, which are divided into superficial and deep layers by a deeper layer of the crural fascia. The tibial nerve innervates the muscles of this compartment.
- Lateral compartment: Contains the fibular muscle group, innervated by the superficial fibular nerve.
The crural fascia is anchored to the fibula by connective tissue septa, distinguishing the anterior and posterior intermuscular septa.
In older texts, the fibular group is sometimes categorized with the extensors due to developmental origins. However, this grouping can be confusing, as these muscles primarily cause plantar flexion at the ankle joint, with tendons that run behind the axis of extension-flexion.
3. Classification
3.1. Anterior compartment
All muscles of the anterior compartment are innervated by the deep fibular nerve.
3.2. Posterior compartment
Also known as the calf musculature, the posterior compartment includes:
- Triceps surae muscle
- Tibialis posterior muscle
- Flexor hallucis longus muscle
- Flexor digitorum longus muscle
- Popliteus muscle
All muscles in the posterior compartment are innervated by the tibial nerve.
3.3. Lateral compartment
Both muscles in this compartment are innervated by the superficial fibular nerve.
4. Vascular supply
The lower leg muscles receive arterial blood from:
Venous drainage is provided by:
- Great saphenous vein (superficial)
- Small saphenous vein (superficial)
- Fibular vein (deep)
- Posterior tibial vein (deep)
- Anterior tibial vein (deep)
- Popliteal vein (deep)