Your nerve compression could be from low back if u having pain in lower back due to disc degeneration or it could ve tightness of piriformis muscle which is causing sciatic nerve compression.this can be told only  by proper aseesment and  medical history. Reason for Swelling in knee is different , there could be arthritis.kindly start taking physiotherapy treatment for atleast month. Different progressive strengthening exercises and precautions will be told to you by physio as your pain will start decreasing. - check for vit b12 , vit d, uric acid as 100% treatment result depends on nutrition status of bones, muscles and nerve.