I hurt on the outside of my knees it stings and burns what's up?

Many reasons: Lateral (outer) knee pain common causes include arthritis, knee-cap problems, lateral meniscal tear, itb syndrome, bursitis, lateral ligament complex injury, loose bodies, fracture and bone bruise. Rarely, popliteus tendinitis and peroneal nerve can cause lateral sided symptoms. Remember, the low back can also refer pain to the outside of the knee.