Layer-by-layer structure and fasciae
The skin of the posterior thigh region is relatively thin and mobile. Beneath it lies a weakly developed superficial fascia containing superficial veins and cutaneous nerves, specifically the posterior femoral cutaneous nerve (n. cutaneus femoris posterior), which provides sensory innervation to this area.
Deeper lies the dense fascia lata (fascia lata), surrounding all the muscles of the thigh. On the lateral surface it forms a powerful thickening — the iliotibial tract (tractus iliotibialis). In the posterior region, the fascia lata forms an isolated posterior fascial compartment (compartimentum femoris posterius), containing the flexor muscles, major vessels, nerves, and lymph nodes.
Thigh muscles
The posterior fascial compartment contains the flexor muscles. Their main function is flexion of the leg at the knee joint and extension of the thigh at the hip joint. Innervation is provided by the sciatic nerve (n. ischiadicus). The anterior wall of this compartment is formed by the deep adductor magnus muscle (m. adductor magnus).
| Muscle | Location | Origin | Innervation |
|---|---|---|---|
| Biceps femoris (m. biceps femoris) | Lateral | Ischial tuberosity (long head), femur (short head) | L4–S2 |
| Semitendinosus (m. semitendinosus) | Medial | Ischial tuberosity | L4–S1 |
| Semimembranosus (m. semimembranosus) | Medially (deeper) | Ischial tuberosity | L4–S1 |
Topographically, the anterior and medial surfaces of the thigh feature the sartorius muscle (m. sartorius), rectus femoris muscle (m. rectus femoris), vastus medialis muscle (m. vastus medialis), as well as the iliopsoas muscle (m. iliopsoas) and the tensor fasciae latae muscle (m. tensor fasciae latae). The medial group also includes the adductor longus (m. adductor longus) and gracilis (m. gracilis) muscles.
Pelvic topography and lacunae
Vessels and nerves emerge from the pelvic cavity through special openings. In the gluteal region, the main landmark is the piriformis muscle (m. piriformis). The superior gluteal vessels, which supply blood to the gluteus medius and minimus muscles, pass through the suprapiriform foramen. The inferior gluteal vessels, sciatic nerve, posterior femoral cutaneous nerve, and internal pudendal neurovascular bundle emerge through the infrapiriform foramen.
Anteriorly, beneath the inguinal ligament (lig. inguinale), in the subfascial layer, there are two spaces separated by a dense fibrous band—the iliopectineal arch (arcus iliopectineus):
- Muscular lacuna (lacuna musculorum) — the lateral space.
- Vascular lacuna (lacuna vasorum) — the medial space.
Blood supply and venous drainage
The primary blood supply to the posterior muscle group is provided by the perforating arteries and veins (aa. et vv. perforantes), which pierce the tendons of the adductor muscles. Throughout its course, the sciatic nerve is accompanied by a slender companion artery (a. comitans n. ischiadici), branching from the inferior gluteal artery. Deep near the quadratus femoris muscle run the medial circumflex femoral vessels (a. et v. circumflexae femoris mediales).
Superficial veins play an important clinical role. The superficial epigastric vein (v. epigastrica superficialis) collects blood from the lower abdomen and drains into the femoral vein (v. femoralis) or great saphenous vein (v. saphena magna). It forms key anastomoses: cavacaval (with the thoracoepigastric vein) and portosystemic (with the paraumbilical veins).
In the popliteal fossa, the neurovascular bundle continues onto the leg. Here pass the popliteal artery and vein (a. et v. popliteae), and the sciatic nerve divides into the tibial (n. tibialis) and common fibular (n. fibularis communis) nerves. Blood supply to the knee is provided by the articular network, which includes the superior and inferior lateral genicular arteries, as well as the middle genicular artery.
To avoid confusing the contents of the lacunae beneath the inguinal ligament, remember the rule: vessels are always located more medially (closer to the body centerline), forming the vascular lacuna, while muscles are located more laterally, within the muscular lacuna.
Class and exam questions
Which muscles form the posterior group of the thigh?
The posterior group includes the biceps femoris (located laterally), as well as the semitendinosus and semimembranosus muscles (located medially). Anterior to them lies the adductor magnus muscle.
Where do most muscles of the posterior thigh originate?
All flexor muscles of the posterior fascial compartment, with the exception of the short head of the biceps femoris, originate from the ischial tuberosity (tuber ischiadicum).
What separates the muscular and vascular lacunae?
These spaces are separated by the iliopectineal arch (arcus iliopectineus) — a dense fibrous band extending from the inguinal ligament to the iliopectineal eminence.
Which nerve innervates the posterior thigh muscle group?
Innervation is provided by the sciatic nerve (n. ischiadicus), specifically its branches originating from spinal segments L4–S2.
What else to study on this topic
- Topography of the femoral triangle and anterior thigh region
- Cavacaval and portosystemic anastomoses of the anterior abdominal wall
- Contents of the suprapyriform and infrapyriform pelvic openings
- Formation and branches of the genicular articular network (Rete articulare genus)
- Topography of the popliteal fossa and transition of vessels to the leg
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