Arthritis in knee resulting in me not wanting to go for a walk….

I know there have been many threads on the subject but I just wanted to ask people if they can make sense of or recognise my problem. I’ve had arthritis in my knee for years but haven’t seen a doctor or osteopath for @ 10 years as I’ve been managing it myself. I used to go to the gym and strengthen the muscles around my knee but stopped going when the pandemic started. The result being I’ve lost those muscles. And I’ve stupidly put weight on recently which always goes onto my legs ( I’m a proper hips and thighs person). It doesn’t cause me any pain usually; sometimes feels a bit sore on the inside of my knee. But what I don’t understand is this. I can walk round the house perfectly normally, apart from being a bit stiff if I’ve been sitting down for a while. Same with walking round the garden. But if I go for a walk I can’t seem to walk properly. Even if I don’t try to stride out but walk slowly I walk in a very strange way and my whole body aches from being tense. The knee does lock slightly every so often ( never in the house) which I suppose makes me tense. But it means I no longer want to go for a walk and, when I do I don’t enjoy it. The only time I feel happy is walking uphill but I have to walk quite a distance to get to the nearest slope. I’ve put myself on a strict diet and have started doing the exercises the hospital gave me years ago ( which I should have continued to do, especially when I stopped going to the gym). I am going to see my osteopath in a few weeks time ( I’ve avoided going anywhere because of covid) and have been putting ibuprofen on it which seems to be working better than voltarol but it puzzles me why I can walk in the house but not outside. I think it’s psychological. I just wondered if anyone else had ever had the same problem. I’ve got a patella strap but using it does actually make my knee sore. I use walking poles as well.