sciatica and knee pain

Knee 'block'? .. Leg pain?
Occasionally when I'm on the shins, (thus: http://www.sciatica.org/images/12poses/yoga2008_55.jpg .. just not as creepy) I get this horrible pain in my knee and feels as if he were locked up and I can not move, but I stretch my legs calm and well wait and leaves. Today though my knee did when it happened this loud pop and now my whole leg hurts. What is wrong?
Locking of the knee: The inability to straighten or bend either knee. See Books in free access on the knee lock down. See detailed information below for a list of 18 cases lock the knee, including diseases and drug causes side effects.
Boulder Chiropractor | Co sciatica and knee pain

