freaky coincedence but is this the pain that originates from the bottom of your back just under the bone that curves slightly upwards and pain radiates toward the hip area and heads down the other side of the leg and stops at the knee. If this is what you have it's a strained muscle.
aka piriformis syndrom. These "trigger points" are all connected I went to a Chinese massage therapist. One website recommended me to put a tennis ball on the spot and lie on it. Rolling those trigger points away. Hurts like a bitch, but do you wanna get better. Also you might wanna cross train and no put too much strain on the bugger, especially if you are on NSAIDS. Just got over this injury. Took about 2-3 weeks, but then everybody is different.