A random question, don't worry AT ALL if you don't have time for it, but ... what exercises would you do if you have heaps of pent up energy but a bad knee, and very weak arms (the latter not through injury, all I mean is that something like push-ups is not currently an option!)?
I am not so sure if you mean just gym exercises... but first off i would recommend swimming or the cross trainer if you have lots of energy but a bad knee as those are usually ok to do despite having knee pain. Though not sure if cardio is the goal, but with gym exercises/strength training i would mayb do a circuit for upperbody.... such as picking maybe 8 exercises targetting the different parts of your upperbody and then doing 8-15 reps for each exercise and doing the whole thing 3-5 times! Otherwise i find that shoulder workouts are always tough and great if i have alot of energy such as doing military presses or side flies etc.
But remember, if you are "weak" in something, then that is what you should do more of to work up your strength in that area :) You can do push ups on your knees or against a wall.... we all start somewhere! But when it comes to pain in knees or back, if you find that you can do some form of exercise without any pain then its usually fine... but if you feel some type of pain or weird tingly feeling then maybe abstain from that exercise form.
Oh and hey if you don´t mind I have a question to you ;) I am sure you maybe already did a post about this topic ;) but at the moment I often struggle with anger and rage of myself ;) especially when others want to help me overcoming some fears of my ED :( but maybe I am also still so angry on myself for still having ed related thoughts? ;) It would be so lovely to hear from you of how you deal with such feelings ;) thaaaaanks in advance, and I hope so much you are fine ;)