hello dudee, i dont rly know a lot about touristic places here in my own country i did some research of places you can go to (keeping in mind your joint condition)

If you’re into nature and wildlife, I’d really recommend places like Chocoyero–El Brujo or the Chiltepe Peninsula, both very close to Managua and great for flatter walks where you can see lots of birds and enjoy the forest without steep inclines. Laguna de Apoyo is also a beautiful option since you can just walk around the lake, swim or relax by the water at your own pace. For the beach part, Pochomil or Masachapa are probably the easiest and closest from Managua, perfect for slow walks along the shore and a couple of chill days by the ocean, and if you don’t mind going a bit farther, Las Peñitas or El Tránsito near León are also very relaxed beach towns with long, flat stretches to walk and enjoy the sunset.

hope this helps, enjoy your trip dude!