Back injury resulting in nerve problems will present as pain or numbness spreading from back/buttock down along your leg, with or without "pins and needles" sensation or weakness in your leg/foot/buttock, ON TOP OF your main back pain.
The presence of one or more of these signs usually necessitate a referral to a spine specialist by your GP so that an MRI scan can be done to evaluate both your spine as well as your nerves (remember X-rays CANNOT visualise nerves).
