Dr. Ebraheim’s educational animated video describes the anatomy of the soleus muscle.
The soleus is a muscle located beneath the gastrocnemius muscle in the superficial posterior compartment of the lower leg.
Four compartments in the leg:
1-Anterior compartment
2-Lateral compartment
3-Deep posterior compartment
4-Superficial posterior compartment.
Origin: the origin of the soleus muscle comes from the upper 1/3 on the back of the tibia, from the middle 1/3 of the medial border of the tibial shaft. It also arises from thee back of the head of the fibula and the upper 1/3 posterior surface of the fibular shaft and the fibrous arch that lies between the tibia and fibula.
Insertion: the soleus muscle then unites with the gastrocnemius to form the Achilles tendon which inserts into the back of the calcaneus.
Innervation: the soleus muscle is innervated by the tibial nerve. The tibial nerve passes behind the muscle through the fibrous arch of the soleus.
Function: the soleus muscle is a plantar flexor of the ankle. The Achilles tendon is an extension of the calf muscles.
Clinical situations:
1-Compartment syndrome of the leg and soleus muscle: in compartment syndrome, the pressure increases. It affects the microcirculation of the leg. If compartment syndrome is not urgently treated by fasciotomy, it may cause tissue ischemia and death.
•Posteromedial incision is placed 2 cm posterior to the posterior margin of the tibia.
•Opening of the superficial posterior muscle compartment.
•Opening of the deep posterior muscle compartment. The soleus muscle may hide the deep posterior compartment. On the medial side, take down soleus insertion to access the deep posterior compartment.
The Achilles tendon inserts into the calcaneus.
2-Achilles tendonitis: irritation and inflammation due to overuse. Pain, swelling and tears within the tendon.
3-Bursitis of the retrocalcaneal bursa: retrocalcaneal bursitis is a common cause of ankle pain in athletes. Retrocalcaneal bursitis is inflammation of the bursa located between the calcaneus and the anterior surface of the Achilles tendon.
4-Achilles tendon rupture: rupture of the Achilles tendon may occur above the calcaneal insertion of the tendon.
The watershed zone is the part of the tendon that has the worst blood supply. The watershed zone is a very narrow area in width between 2-6 cm proximal to the calcaneus and is prone to rupture. The Achilles tendon is prone to tendonitis or tendon ruptures within this watershed zone due to limited blood supply.
Thompson test: when the examiner squeezes the calf muscle, there should be motion of the foot, which is a sign of an intact Achilles tendon. With complete tear of the Achilles tendon, there will be no movement of the ankle when performing the Thompson test. The tendon is noticeably intact in the normal ankle compared to the ankle that has a rupture of the Achilles tendon.
5-Gastrocnemius tightness vs. Achilles tightness: dorsiflexion of the ankle is limited with tightness of the gastrocnemius muscle. The gastrocnemius muscle spans across the knee joint. The gastrocnemius muscle relaxes with flexion of the knee and this improves the ankle dorsiflexion. This knee flexion test measures the range of ankle dorsiflexion with the knee flexed and the knee straight. More ankle dorsiflexion with the knee flexed indicates gastrocnemius tightness.
With Achilles tendon tightness or contracture, ankle dorsiflexion is the same with knee extension and flexion. The degree of dorsiflexion does not change regardless of the knee position involving tightness of the Achilles tendon.
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Background music provided as a free download from KZread Audio Library.
Song Title: Every Step