Ay stiffness in the morning?
Slump test positive?
does compresion of the head increases the pain?
Is the patient a drug user?
any psychological problems?
Is the injury a workers compensation?
ask the patient to do long sitting while lying supine in bed if the patient is able to do that discharge the patient. Also, try ultrasound I bet he will feel pain.
You are waisting your time with this patient.
good luck