I Have Been Having Excruciating Pain In My Left Knee.

I have been having excruciating pain in my left knee. I went to an orthopedic doctor and after X-rays said I have osteoarthritis. He gave me a shot that was supposed to improve mobility but the pain only got worse, and started radiating down my leg, sometimes making my foot feel like it was going to sleep but didn't. I started acupuncture to possibly help, and it would for about a day or two then pin was back in full force. After another trip to the orthopedic doctor, he did an ultrasound and found a cyst in my knee. He drained it and again felt better for a couple of days, but then the pain returned now radiating up to my hip and down my leg. I have trouble walking and it sometimes feels like my knee is going to give out. It hurts to sit for any length of time as the pain goes up the back of my leg and down my calf. Still seeing acupuncturist and she worked on my sciatica. Feels better now but that was today. Sitting is still a problem but the pain has eased for now. If I go back to my orthopedic doctor he tells me I need a full knee replacement. What are your thoughts?