A series of perforator veins interconnect the superficial and deep systems. In the standing posture, the veins of the leg have to handle an exceptional load as they act against gravity when they return the blood to the heart. The venous valves assist in maintaining the superficial to deep direction of the blood flow.Superficial veins:

Great saphenous vein
Small saphenousDeep veins:

Femoral vein, whose segments are the common femoral vein and the subsartorial vein. Popliteal vein
Anterior tibial vein
Posterior tibial vein
Fibular vein

Nerve supply
The sensory and motor innervation to the lower limb is supplied by the lumbosacral plexus, which is formed by the ventral rami of the lumbar and sacral spinal nerves with additional contributions from the subcostal nerve (T12) and coccygeal nerve (Co1). Based on distribution and topography, the lumbosacral plexus is subdivided into the lumbar plexus (T12-L4) and the Sacral plexus (L5-S4); the latter is often further subdivided into the sciatic and pudendal plexuses:The lumbar plexus is formed lateral to the intervertebral foramina by the ventral rami of the first four lumbar spinal nerves (L1-L4), which all pass through psoas major. The larger branches of the plexus exit the muscle to pass sharply downward to reach the abdominal wall and the thigh (under the inguinal ligament); with the exception of the obturator nerve which pass through the lesser pelvis to reach the medial part of the thigh through the obturator foramen.
Aneurysmal bone cyst (ABC) is a non-cancerous bone tumor composed of multiple varying sizes of spaces in a bone which are filled with blood. The term is a misnomer, as the lesion is neither an aneurysm nor a cyst. It generally presents with pain and swelling in the affected bone. Pressure on neighbouring tissues may cause compression effects such as neurological symptoms.The cause is unknown. Diagnosis involves medical imaging. CT scan and X-ray show lytic expansion lesions with clear borders. MRI reveals fluid levels.Treatment is usually by curettage, bone grafting or surgically removing the part of bone. 20–30% may recur, usually in the first couple of years after treatment, particularly in children.It is rare. The incidence is around 0.15 cases per one million per year. Aneurysmal bone cyst was first described by Jaffe and Lichtenstein in 1942. Signs and symptoms
The afflicted may have relatively small amounts of pain that will quickly increase in severity over a time period of 6–12 weeks. The skin temperature around the bone may increase, a bony swelling may be evident, and movement may be restricted in adjacent joints.Spinal lesions may cause quadriplegia and patients with skull lesions may have headaches. Sites
Commonly affected sites are metaphyses of vertebra, flat bones, femur and tibia. Approximate percentages by sites are as shown:
Skull and mandible (4%)
Spine (16%)
Clavicle and ribs (5%)
Upper extremity (21%)
Pelvis and sacrum (12%)
Femur (13%)
Lower leg (24%)
Foot (3%)

Causes
Aneurysmal bone cyst has been widely regarded a reactive process of uncertain cause since its initial description by Jaffe and Lichtenstein in 1942.