strained back; slipped disc; lumbosacral strain
Common term for sudden acute lower back pain, often from lifting or twisting. Not a formal medical diagnosis; covers muscle strain, disc issues, and similar conditions.
I threw my back out trying to lift a heavy box.
ぎっくり腰で動けなくなって、病院に行った。
I couldn't move because of a strained back and went to the hospital.