Nervous anatomy of lower limb
The following structures emerge from the pelvis through greater sciatic foramen into the gluteal region:
Above the piriformis
Superior gluteal nerve
Superior gluteal vessels
Below the piriformis
Inferior gluteal nerve and vessels
Pudendal nerve and vessels
Nerve to obturator internus
(v)Posterior femoral cutaneous nerve
(vi)Nerve to quadratus femoris
Superior gluteal nerve supplies both gluteus medius and minimus and ends in tensor fascia lata. It has no cutaneous distribution.
Superior gluteal artery gives superficial and deep branches. The superficial branch enters deep surface of gluteus maximus to supply the muscle and skin over it. The deep branch passes laterally between gluteus minimus and gluteus medius and further divides into upper and lower branch. The upper branch forms the anastomosis at the anterior superior iliac spine and lower supplies gluteus minimus and medius and forms the trochanteric anastomosis.
The inferior gluteal nerve passes below the piriformis to sink into deep surface of gluteus maximus.
The inferior gluteal artery supplies piriformis, obturator internus, and gluteus maximus.
The pudendal nerve (S2–S4) after emerging below the piriformis makes a forward turn around the back of sacrospinous ligament and ultimately leaves the buttock by passing through lesser sciatic foramen to pass through pudendal canal.
The internal pudendal artery follows a similar course to that of the nerve and lies lateral to the nerve. A companion vein lies on each side of the artery.
The nerve to obturator internus (L5, S1, S2) lies lateral to internal pudendal artery and loops around base of ischial spine to finally supply obturator internus and superior gemellus.
The sciatic nerve (L4, L5, S1–S3) emerges from below piriformis muscle. It is typically 2 cm wide at its origin, thus being the thickest nerve in the body. It lies more laterally than the inferior gluteal and pudendal nerve and vessels. It passes upon the ischium over the posterior aspect of acetabulum. It comes in contact with ischial tuberosity at a point one third of the way from ischial tuberosity to the posterior superior iliac spine, its surface marking for entry of nerve into the gluteal region. It goes vertically downward going over the posterior surface of obturator internus and quadratus femoris and finally entering the hamstring compartment of the thigh, where it lies anterior to the long head of biceps femoris. In the upper part of the popliteal fossa, it divides into tibial and common peroneal in most of cases. Occasionally, there is a high division and the two components may leave the pelvis separately.
The posterior femoral cutaneous nerve (S1–S3) emerges below the piriformis, and during its course in the gluteal region, it lies on the sciatic nerve under cover of gluteus maximus. Below the buttock, the nerve goes vertically down as low as the mid calf. It lies below the fascia lata, superficial to hamstrings which separate it from sciatic nerve. It gives gluteal branches which curl around lower border of gluteus maximus to supply the skin over buttock convexity. The perineal branch supplies the posterior part of scrotum or labium majus.
It is noticeable that the segments of this nerve are also those of pelvic parasympathetic nerves which supply pelvic viscera. Pain from the pelvic disease is often referred over the supply of femoral cutaneous nerve and this pain should be distinguished from sciatica.
The nerve to quadratus femoris (L4, L5, S1) lies over the ischium anterior to the quadratus femoris. It gives an articular branch to the back of hip joint and supplies quadratus femoris and inferior gemellus.
5.2.2 Anterior Compartment of the Thigh 
126.96.36.199 Superficial Nerves
Femoral branch of genitofemoral nerve
Medial, intermediate, and lateral femoral cutaneous nerve
Cutaneous branches of obturator nerve
Ilioinguinal nerve is derived from first lumbar nerve. It supplies the skin of root of the penis, anterior one third of scrotum, and small area of thigh below medial end of inguinal ligament.
Genitofemoral nerve is derived from first and second lumbar nerves. But the femoral branch has fibers from L1 only. It supplies the skin over femoral triangle.
The medial femoral cutaneous nerve is a branch of femoral nerve (L2, L3). It supplies medial side of thigh.
The intermediate femoral cutaneous nerve (L2, L3), again a branch of femoral nerve after piercing the sartorius and fascia lata, supplies front of thigh.
The lateral femoral cutaneous nerve is a branch of lumbar plexus (L2, L3). It gains entry to the thigh by piercing the fascia lata and divides into anterior and posterior branches. The anterior branch supplies the anterolateral surface of the thigh, whereas the posterior branch supplies the skin on posterolateral aspect from the level of greater trochanter to the mid thigh. The nerve if compressed while passing through inguinal ligament causes pain and altered sensation in lateral side of thigh (meralgia paraesthetica). Sometimes, it may get compressed while passing through iliac fascia as well. The treatment of this condition requires division of inguinal ligament and freeing the nerve from any compression.
The cutaneous branches of obturator nerve (L2–L4) pass to the skin over the medial side of thigh.
Patellar plexus: It is a network of communicating twigs present in subcutaneous tissue over and around the patella and patellar ligament. It receives contribution from the terminal branches of medial and intermediate femoral cutaneous nerves, anterior branch of lateral femoral cutaneous nerve, and infrapatellar branch of saphenous nerve.
5.2.3 Superficial Arteries
There are four cutaneous branches of femoral artery:
Superficial circumflex iliac artery
Superficial epigastric artery
Superficial external pudendal artery
Deep external pudendal artery
Superficial circumflex iliac artery passes up below the inguinal ligament to the anastomosis at anterior superior iliac spine.
Superficial epigastric artery crosses inguinal ligament and runs toward umbilicus.
Superficial external pudendal artery emerges from saphenous opening, passes in front of spermatic cord (round ligament), and goes to the penis and scrotum (labium majus).
Deep external pudendal artery pierces fascia lata and goes behind spermatic cord (round ligament) to supply the skin of scrotum (labium majus).
5.2.4 Superficial Veins (Fig. 5.3)
Venous anatomy of lower limb
The great saphenous vein (GSV) being the longest vein in the body runs from foot to groin, beginning as upward continuation of the medial marginal vein of foot. This vein runs between superficial and deep fascia, and on ultrasound, it gives the appearance of Egyptian eye. It goes upward in front of medial malleolus, crosses lower fourth of medial surface of tibia obliquely, and runs behind the medial border of tibia toward the knee where it lies palm breadth behind medial border of patella. It curves forward around medial convexity of the thigh and ends by piercing deep fascia and passing through cribriform fascia, where it joins femoral vein. Normal diameter of GSV is 5–6 mm in thigh and 2–3 mm in calf. There are about 20 valves. Incompetence of these valves is a cause of varicosity of the vein. Four tributaries join great saphenous vein in the region of saphenous opening. They are superficial circumflex iliac, superficial epigastric, and superficial and deep external pudendal vein (Fig. 5.4) near the saphenofemoral opening. Superficial external pudendal artery crosses at the level of saphenofemoral junction (SFJ) but many a times, it passes behind the GSV. Saphenofemoral junction is 4 cm below and lateral to pubic tubercle. Apart from the tributaries near SFJ, there are other tributaries as anterior accessory and posterior accessory veins draining into GSV. GSV is in close proximity to saphenous nerve which is the largest branch of femoral nerve purely sensory in origin. This nerve is in close proximity to GSV in lower part and that is why it is likely to damage if stripping or endovenous procedure is done in the leg.
Short saphenous vein (SSV) arises from lateral side of foot and drains in popliteal fossa at variable positions. It usually penetrates the deep fascia in the mid calf and then, it runs between two heads of gastrocnemius to open in popliteal vein. Sural nerve is in relation with SSV and is likely to be damaged during surgery of SSV mainly in the lower part as it is in close proximity in that part. Sometimes, the vein of Giacomini which connects SSV with GSV is present and that may be the reason for recurrence of varicose veins after surgery or endothermal treatment.
There are numerous perforating (anastomotic) veins which connect great saphenous vein with deep veins of the calf. They are variable in position but the constant ones are the following :
Just below the medial malleolus
10 cm above the medial malleolus
Little below the middle of the leg
Just distal to the knee
In lower thigh joining great saphenous vein or one of its tributaries to the femoral vein in adductor canal
The perforators in the leg may connect the posterior arch vein which joins the great saphenous vein below the knee. Also, some perforating veins join the venae comitantes of the posterior tibial artery, whereas others communicate with venous plexus of the soleus. The valves in the perforating veins are directed from superficial to deep and are found where the veins pierce the deep fascia and also where they communicate with the deep veins. The blood in the superficial system flows to the deep system of veins which is further pushed upward by the pumping action of the soleus and other calf muscles. If the valves in the perforators become incompetent, the flow becomes reversed resulting in varicose veins. Although deep venous insufficiency is common and important, the anatomy of deep vein valves is poorly understood. A study was conducted to investigate the location, number, and consistency of venous valves in the femoral and popliteal veins in normal subjects. All studies were cadaveric and subjects ranged from stillborn fetuses to 103 years of age. Studies suggested that femoral veins contain between one and six valves, and popliteal veins contain between zero and four valves. Deep vein valves were consistently located in the common femoral vein (within 5 cm of the inguinal ligament), the femoral vein (within 3 cm of the deep femoral vein tributary), and the popliteal vein near the adductor hiatus. Valves are consistently located at specific locations in the deep veins of the leg, although there is often significant variability between subjects .
Arterial anatomy of lower limb
The femoral artery enters the thigh at midinguinal point (point between anterior superior iliac spine and pubic symphysis) as a continuation of external iliac artery. Here, it lies over the psoas major. It is here where its pulsation can be felt and catheterization can be done. It emerges from the femoral sheath, goes downward, and enters adductor canal deep to sartorius.
It has four small branches below the inguinal ligament and just below the ending of femoral sheath gives off a large deep branch, the profunda femoris, the chief artery of the thigh.
The profunda femoris artery usually supplies all muscles of thigh. It arises from lateral side of femoral artery about 3–4 cm distal to the inguinal ligament and then curves down deep to it, passing between pectineus and adductor longus, whose upper border separates femoral and profunda arteries.
In addition to perforating arteries and muscular branches, it gives off large lateral and medial circumflex femoral artery.
The lateral circumflex femoral artery passes between branches of femoral nerve and divides into three branches beneath sartorius. The ascending branch runs up on the vastus lateralis. It gives a branch to the trochanteric anastomosis and passes on toward anterior superior iliac spine where it terminates by anastomosing with superficial and deep circumflex iliac and superior branch of superior gluteal artery. The transverse branch passes across vastus lateralis and spirals around the femur to form part of the cruciate anastomosis. The descending branch runs downward with nerve to vastus lateralis in a groove between anterior edges of vastus lateralis and vastus intermedius.
The medial circumflex femoral artery arises from medial side of profunda. It gives an ascending branch to the trochanteric anastomosis and a horizontal branch to the cruciate anastomosis.
The four perforating arteries pass backward, through adductor magnus, first pass above, second through, and third and fourth below adductor brevis. They supply hamstring and adductor muscles.
5.2.6 Femoral Vein
It enters through the lower part of femoral triangle lying posterior to femoral artery. It goes upward through femoral triangle and comes to lie medial to femoral artery. A tributary corresponding to profunda femoris artery drains into it and just below the femoral sheath the great saphenous vein joins it. It bears 4 or 5 valves, the most constant ones being just above the junction with profunda and great saphenous vein. The position of femoral vein in the living body is found by feeling the pulsations of the femoral artery and the femoral vein lies immediately medial to it . More than 80 % of blood flow in the lower limb is through deep veins.