I can only speak of my own experience and everyone is different. I have arthritis in my knees which was diagnosed when i had an MRI and subsequent arthroscopy on my right knee 5 years ago. I ahd been running for 5 years prior to injury. I had the operation and was told by the consultant 'you do realise if you run you will end up having to have knee replacements' to which i replied 'you do realise if i don't run i will end up with diabetes and coronary artery disease' (I have a terrible family history of this). Any way after 9 months of no running i started again and my knees were very stiff and sore. I started doing some toning and strengthening exercises in the gym too and strengthened the muscles that support my knees. slowly my knees became less sore but i'm talking months and months. Now 5 years later i hardly have any pain and have ran a marathon a year and many many smaller races in thst time. Anything you read about arthrits tells you that if you keep the joints moving they will be more supple and less painful.
I do think that losing some weight would be helpful but you are currently stuck between a rock and a hard place. I expect they are telling you to exercise to help with weight loss but that exercise is tricky due to the knees. In a nut shell, and this is my opinion only, i think you can expect to be sore but it shouldn't make thinsg any worse. Even without the arthritis if you were to take up running you would be stiff and sore in the beginning. Only you know your body and i am a great fan of the old phrase 'use it or lose it.' Good luck!!
Well done ladies!! it's brilliant that you're out there doing it. A very cheesy quote but one i like 'you are lapping everyone on the couch' Speed is not the issue it's just getting out there that's important. I live in Gloucester and run with Almost Athletes, based in Cheltenham so will hopefully see you at some local races. I'd highly recommend aiming to do the Cheltenham Park Run to give you a focus. It's on every saturday and extremely beginner friendly. Pick a realistic date and pledge to do it together you'll have a fab time