And do you think trainers know much more? I've seen many give the wrong advice on how to use some machines. Machines aren't the best to use!
Just like many doctors aren't good.
What Is wrong with interval training? The clip on Mercola is excellent! You can do many different forms of interval training must I show a different one each time?
Talk is cheap and Paxiled hasn't given you an answer to your question.
Not knowing what your injury is see if you can try the following.
https://youtu.be/BBdRzqsYX1g
https://youtu.be/oH2OAERhr-U
https://youtu.be/1TzI8j776Z8
https://youtu.be/IBIK38Sg3as
Running doesn't really exercise your core, so the knee isn't a problem there. What I'd recommend is seeing a physical therapist who can show you tons of core building exercises, as well as exercises to strengthen your knee and the muscles around it. Or you can go to a gym and get a personal trainer to show you. Or go on You Tube. Or wait for someone here to mention a thousand exercises, because there are literally thousands of different exercises to work on different parts of your core, not that working on your core has proven to be all that beneficial. In fact, some believe all the core building by serious athletes today has caused harder to treat core injuries that take longer to recover from, but that's another story. As for aerobics, there's swimming, bicycling (if it doesn't hurt your knee), walking when you're up to it, and even working out quickly with light weights so you get out of breath. You can still do abs, which are quite vigorous exercises. How bad is your knee, have you seen someone, and have you been recommended to see a physical therapist to rehab?