It seems to me that your patient is suffering from Acute Mechanical Backache (Back pain less than 6 week duration) with injury to both anterior and posterior elements as the history and pain pattern or provocation on testing the spinal movements suggest. Please perform additional examination of the Wikipedia reference-linkSacroiliac joints and hip joint to rule out any problems in these region. Perform a detailed neurological examination of lower limb for spine including sensory, motor and reflex testing examination. Let me know about your findings.