I have sharp pain from my buttocks all the way down my left leg sometimes it hurts to sit stand or bend...what could it be?

Sciatica?: You are desscribing a condition called sciatica. This is an irritation of the sciatic (cy-attic) nerve as it come off your lower spine. This can be due to disc protrusion or arthritis or instability of the vertebrae. Usually treated with rest, heat or ice, anti-inflammatories and keeping the knees bent slightly. May need parenteral anti-inflammatories and pain meds and pt. See your pcp.Google.