Trouble walking and standing cramping in knees? and not sure if related but pressure/pain in lower back can't stand for long periods. any thoughts?

A Few: Pinched nerves (radiculopathy) in the lower back can radiate pain down the legs. However, there maybe iliotibial band syndrome as well, a tough band of tissue that goes from your hip to knee, if it becomes inflammed, then problems arise. A few orthopedic test in the office can help your doctor figure out which imaging studies to do next.

Stand: I agree - the most likely culprit is nerve compression/problems. See your neurologist and or orthopedist for an evaluation.