A complete sciatic nerve compression leads to weakness of the knee flexors and all muscles below the knee. Fortunately this is rare, and can be avoided by frequent positions changes, choosing a seat that ends 1-2 inches from the back of the knee, and slopes gently down at the front edge. Using a portable seat cushion can help when the only seating option is a hard surface like bleacher seats. Entrapment of the common peroneal nerve is the most frequent entrapment neuropathy in the leg, particularly, in the region of the fibular head on the outside of the knee. This leads to a foot drop and numbness over the outside of the lower leg and on the top of the foot.
Pressure can come from crossing legs or recurrent stretch injury as a result of an unstable ankle.
Knee high stocking that are too tight and casts for fracture immobilization can also cause compression. Avoidance of crossing your legs and tight stockings pan help prevent this. Entrapment of the posterior tibial nerve can occur below and behind the medial malleolus on the inside of the ankle. Flat feet with overuse of stabilizing muscles whose tendons pass through the area can contribute to this. Well fitting, possibly custom arch supports can reduce this problem.