Throbbing knee pain that hurts to sit/lay down?help

It depends: Knee pain can be caused by patella chondromalacia or internal derangement. It can also be referred from an occult hip or lumbar spine problem. Try vmo exercises & nsaids. Persistent pain calls for an x-ray and evaluation by a healthcare professional.

Knee pain: Consider inflammation, injury to cartilage, meniscus, patella, overuse, etc. Also consider referred from spine (disc herniation, etc.).