What would cause intense localized knee pain (wakes from sleep) that only occurs at night in 1 knee. no injuries, no pain in day. worsening 3 weeks.

Orthopedic specialis: If the discomfort is definitely arising in the knee and only occurs while in bed, there is a positional component to it. It may occur when leg muscles are completely relaxed and, at this point a cartilage, tendon or ligamental structure may become impinged. An orthopedic surgeon is best qualified to evaluate and advise you. A knee X-Ray or mri may be recommended in order to make a diagnosis.