A couple of tips that may help with maintaining friendships when you can't meet up physically very often:

- Being curious about other people - people love to talk about themselves and their feelings. You don't have to solve other people's problems, you don't have to take on their pain or perform emotional labour... just listening brings people closer to you. And in return they will ask you about your life.

- Sharing enjoyable moments. Are there movies/TV shows/music that you enjoy as an adult? Can you find friends that also enjoy this? One of the ways I love to spend quality time with my best friend is to watch shows with him simultaneously while we're both in our separate houses, but we have our phones on speaker so can react to the show in real time. You could do something similar with your friends. Doesn't require making big plans, or going outside your house. My brother has "cooking days" with his friend who is in another state, where they just cook together, separately, joined via Zoom. You may not want to cook due to your injured knee, but maybe you could bond with people who like playing with cats, or doing craft with their kids, or something you were doing anyway so it's not going to take time away from your "to do" list (as I know that stresses you out)

- Writer's groups. People who Zoom together, writing quietly, but in company.

Just a couple of ideas. No pressure to try any of them.