Knee and calf pain

Hello, I have had ongoing pain in both knees and calves.There was no particular injuries to my legs. I have had 2 arthroscopic surgeries and a partial knee replacement(in right leg) which have not helped with my pain.Both knees hurt about the same.There is a question as the whether or not the pain is coming from my lower back.A MRI shows an assymetric disc bulge at L4-5 and some degenerative changes.There is no evidence of focal disc herniation. What is your opinion on my case ?.Thanks,Lorraine Weeks