A 40-year-old male presents with a two month history of low back pain. You notice that when you meet the patient he is standing so that his trunk is shifted to the left. The patient relates the injury to an incident when he was lifting a heavy box out of the trunk of his car and felt a sharp pain in his lower back. The patient initially thought that the pain would go away as it had with his previous episodes of low back pain but when it did not he went to see his primary care physician. His physician took a series of x-rays and told the patient that he had arthritis of the spine. The patient was prescribed NSAIDs but has made little improvement. Upon further questioning about his present condition, the patient reports that he has noticed over the past two months that his right leg falls asleep a lot, especially when he sits down or bends over. The symptoms are decreased when the patient is standing or when he is lying on his side (he reports that he cannot tolerate lying on his stomach). With the exception of his episodic back pain, the patient's past medical history and surgical history is unremarkable and he states that he is in good health.