Lower extremity blocks can be performed with the patient in various positions (lateral, prone, or supine). Because lower extremity surgery usually requires at least two blocks (sciatic and lumbar plexus or a part of it), and because mobilization of the patient may be difficult or painful (e.g., morbid obesity, arthritis, trauma), the choice of technique takes into consideration the need to limit the mobilization of the patient. For surgery at the knee requiring sciatic and femoral blocks in a trauma patient who cannot be mobilized, anterior approaches to these two nerves are indicated. In contrast, when the patient can assume a prone or lateral position, a parasacral, posterior, or subgluteal approach to the sciatic nerve combined with a lumbar plexus approach is possible.

Some consideration should also be given to the choice of the block according to the associated surgical requirements. For example, placement of the tourniquet at the thigh or the calf requires a lumbar plexus block or a saphenous nerve block, respectively. Although the arthroscopic knee diagnostic procedure may be performed under a single femoral nerve block, any knee surgery involving the posterior aspect of the knee also requires a block of the sciatic nerve. This is accomplished using a parasacral, posterior, gluteal/subgluteal, anterior, and lateral or popliteal approach to the sciatic nerve. Although all these approaches are appropriate for surgery below the knee, it seems that a gluteal/subgluteal or a lateral or posterior popliteal approach is favored. Finally, it is possible to obtain a complete block of the foot with an ankle block. However, the use of a combined sciatic and lumbar plexus/femoral/saphenous provides better postoperative analgesia.