The posterior compartment is further subdivided into a superficial and deep compartment, with a tough intermuscular, deep facial septum interposed between the two.

Look for the most superficial of this group, the gastrocnemius. Notice its two-headed proximal attachment to the femoral epicondyles.

Follow the muscle distally to its tendon, the tendocalcaneus (achilles tendon) and its attachment to the calcaneal tuberosity.

Deep to the gastrocnemius, find the flat soleus. The soleus begins proximally on the tibia and fibula and does not cross the knee. However, the soleus does use the tendocalcaneus for its distal attachment.

The two heads of the gastrocnemius and the soleus make up the so-called triceps surae (leg). This is because of their common distal attachment.

On the superficial and medial surface of the soleus, look for the very thin tendon of the plantaris muscle. If you follow the tendon superiorly, you can find this small muscle crossing the knee. This muscle seems to be a lot like the palmaris longus in the upper limb. Distally, the plantaris attaches, usually by itself, to the calcaneal tuberosity.

Let's now move on to the deep posterior compartment which is deep to the soleus.

The muscles of this region run distally, posterior to the medial malleolus to their insertion sites. Examining the mid-calf region, with the soleus reflected, you should see three separate muscles. From medial to lateral, they are: the flexor digitorum longus, the tibialis posterior and the flexor hallucis longus. Trace these muscles inferiorly and note their positions as they pass posterior to the medial malleolus. From superior to inferior, see the tibialis posterior, the flexor digitorum longus, and finally the flexor hallucis longus. Can you follow the flexor hallucis as it travels inferior to the sustentaculum tali?

Before we leave this deep posterior group of muscles, find the deeply placed popliteus in the depths of the popliteal fossa. It will be deep to the popliteal vessels and tibial nerve. Notice how its fibers run obliquely, superior to inferior from lateral to medial.

Now is a good time to focus in on the blood and nerve supply to this region of the leg.

Remember the popliteal artery on the back of the knee? Remember how at the inferior edge of the popliteus muscle it splits into an anterior tibial and posterior tibial artery?

From this posterior approach, see if you can find the popliteal artery and its two terminal branches, the anterior tibial artery and the posterior tibial artery. The anterior tibial artery may be hard to see, so locate the popliteus muscle first and orient yourself accordingly.

Can you see any venae comitantes within the posterior tibial venous system?

The posterior tibial artery continues for a short distance inferiorly before it gives off the peroneal artery . Find this posterior and lateral artery. It soon disappears under the belly of the flexor hallucis longus. Follow the posterior tibial artery inferiorly to the medial malleolus.

The tibial nerve is the main continuation of the sciatic nerve in the leg. Find this nerve in the posterior compartment of the leg as it runs with the posterior tibial artery, between the flexor digitorum longus medially, and the tibialis posterior laterally. Both the posterior tibial artery and the tibial nerve run together, behind the medial malleolus, splitting into medial and lateral plantar arteries and nerves and distributing themselves to the sole of the foot.