How to keep active when your body fails

I love sport, I always have done. I enjoy tennis, cycling and running. Most of all though, I enjoy football. Its always been the perfect release for me. When i'm on the pitch I feel like my mind is only focusing on the game, i'm fully engaged and its a great way of being mindful without really needing to work at it. Lately though i've been finding it really difficult to keep playing. Part of this has been motivation and the weather but the biggest reason is that my health has not been great. Some of this is temporary issues but the largest two things stopping me are the state of my knees and the state of my lungs.

I have hammered myself for years playing football and as a consequence my knees hurt, quite badly, after every game I play. Most times I can no longer climb a flight of stairs the day after a game. I've been to the physio and have exercises, which I do, but I still have flair ups. The issue stems from a mis-balance in my thigh muscles that pull my kneecaps sideways when I run. As a result, the tissue under my knees swells and hurts. Lately its been not so great and generally speaking knees don't tend to improve with age.

My second issue is that I was recently diagnosed with Asthma. The condition is mild, but its enough to cause me some issues on the pitch and effects my stamina. I've never had the greatest stamina anyway but this has hit my ability to run distances pretty hard.

This basically leaves me one of two choices. The first choice, giving up football, is really not such a great option. I would really miss it and would feel like i'd lost something quite important, not just to my physical health but to my mental health also.

As such i've decided to try a second option, vary my game. I used to play as a winger, lots of running and high impact plays and taclkes. Now i'm having to play a much more patient sitting game and focus on my position and passing. The difficulty for me has been that I've always played on instinct, and now i'm having to work on a much more mental game. This said, if it prolongs my ability to play football into my 40s or even 50s then its worth the effort up front.

Once I get past 50, it is my intention to take up walking football. This is a variant of the sport where running is strictly banned, with the idea that it helps people with reduced mobility. The wikipedia article has more information for anyone that is interested.

https://en.wikipedia.org/wiki/Walking_football