Topography and boundaries
The cruropopliteal canal is located in the posterior fascial compartment of the leg. The space of the canal is formed by muscle masses: it runs strictly between the superficial and deep muscle groups.
The superficial part of the posterior compartment is occupied by the muscles forming the triceps surae (m. triceps surae). These include:
- Gastrocnemius muscle (m. gastrocnemius), which has medial and lateral heads.
- Soleus muscle (m. soleus).
The inlet of the canal is bounded by two main structures:
- Anteriorly — the popliteus muscle (m. popliteus).
- Posteriorly — the tendinous arch of the soleus muscle (arcus tendineus m. solei).
Contents and vascular branches
Right at the canal inlet, at the level of the tendinous arch of the soleus muscle, the popliteal artery (a. poplitea) divides into its two terminal branches:
- Anterior tibial artery (a. tibialis anterior).
- Posterior tibial artery (a. tibialis posterior).
In addition, the topography of this region features an artery that subsequently emerges from the canal at the lower lateral border of the flexor hallucis longus muscle (m. flexor hallucis longus). The exit site is located at the border of the middle and lower thirds of the leg. Further, the vessel runs along the lateral border of the bone, covered by the deep and superficial layers of the leg fascia.
In the lower third of the leg, branches important for collateral circulation depart from the arterial trunks:
- Communicating branch (r. communicans) — anastomoses with the posterior tibial artery.
- Perforating branch (r. perforans) — penetrates into the anterior compartment of the leg through an opening in the interosseous membrane and anastomoses with the anterior tibial artery. It is of immense clinical significance: in cases of hypoplasia or absence of the dorsalis pedis artery (a. dorsalis pedis), this specific branch enlarges and takes over its function.
Adjacent anatomical structures
For a complete understanding of the topography of the region, structures adjacent to the capsule of the knee joint from the posterior aspect should be mentioned:
- Subpopliteal recess (recessus subpopliteus) — a synovial bursa separating the popliteus muscle from the joint capsule. It continuously communicates with the knee joint cavity, and in 20% of cases additionally connects with the tibiofibular joint cavity.
- Bursa of the medial head of the gastrocnemius muscle (bursa subtendinea m. gastrocnemii medialis).
- Semimembranosus bursa (bursa m. semimembranosi), also known as Baker's cyst bursa. Both bursae separate the joint capsule from the muscles internally and communicate with the knee joint cavity in approximately 50% of cases.
Briefly: answers to topical questions
Which muscles form the anterior and posterior walls of the cruropopliteal canal?
The sources do not describe the muscles forming the walls of the canal along its entire length, but they specify the muscles bounding its inlet. The canal is located between the superficial and deep muscle groups of the posterior leg. The inlet is formed by:
- Popliteus muscle (m. popliteus) — bounds the inlet anteriorly.
- Soleus muscle (m. soleus) — its tendinous arch (arcus tendineus m. solei) bounds the inlet posteriorly.
Which nerves and veins pass through the cruropopliteal canal?
The tibial nerve and posterior tibial veins pass through the cruropopliteal canal, forming part of the posterior neurovascular bundle of the leg.
- Tibial nerve (n. tibialis) — passes through the canal and occupies the most superficial position relative to the artery.
- Posterior tibial veins (vv. tibiales posteriores) — accompany the posterior tibial artery.
Also, lateral to the main bundle in this region are the fibular (peroneal) veins (vv. fibulares).
What openings (outlets) does the cruropopliteal canal have?
The cruropopliteal canal has three main openings: one inlet and two outlets.
- Inlet — located superiorly, at the level of the tendinous arch of the soleus muscle.
- Upper outlet — through which the anterior tibial artery passes into the anterior fascial compartment of the leg.
- Lower outlet — located at the medial border of the soleus muscle; through it, the posterior neurovascular bundle exits the canal.
Class and exam questions
Where is the inlet of the cruropopliteal canal located?
The inlet is located beneath the tendinous arch of the soleus muscle, bounded anteriorly by the popliteus muscle.
Into which arteries does the popliteal artery divide within the cruropopliteal canal?
At the level of the tendinous arch of the soleus muscle, it bifurcates into the anterior and posterior tibial arteries.
Where do the vessels exit the cruropopliteal canal?
The exit site is located at the border of the middle and lower thirds of the leg, at the lower lateral border of the flexor hallucis longus muscle.
What else to study on this topic
- Topography of the anterior tibial artery in the lower third of the leg
- Retaining ligaments and osteofibrous tunnels in the ankle region
- Anatomy of the superficial and deep fibular (peroneal) nerves
- Projection lines of the neurovascular bundles of the leg and foot
- Synovial sheaths of the fibular tendons
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