Knee pain without known trauma is either a condition like Rheumatoid Arthitis, internal infection or refered pain from the spine. In general, pain at the Superior Medial location is from the lower Thoracic spine and upper Lumbar area. Pain at the Lateral Superior aspect is from the Lumbo Sacral spine. If you have pain distally, including down to the foot, it is usually from the Lateral Gluteal muscles which have become inflammed over time and are in spasm.
These comments may be disputed by some. Good luck.