Since Last Night I Have Had Severe Pain In Left

Since last night I have had severe pain in left leg starting in anterior and left lateral thigh, throughout knee, and extending down into shin. Able to walk briefly before pain becomes so bad I have to sit down. So far today have taken ibuprofen 800 mg at 8:30 am and 2:15 pm. Minimal relief with med. No falls. Have history of osteoarthritis in lower extremities and lower back but do not routinely take any medication for this. Pain improves when I lift my left leg to rest on the back of the couch. No specific back pain noted.