If I was in this situation I would work my biceps and forearms with weights. Maybe try to do them seated without putting tension on your knee/legs. Just be careful and start out with low weight working your way up to where you can just barely do 12 reps with clean form. I keep track of my progress on my computer and workout between posts some days.
Seated Hammer Dumbbell Curl
http://youtube.com/watch?v=LdnxaIm9n1o
Seated Dumbbell Curl
http://youtube.com/watch?v=ggSmQiAfyd0
Wrist Curl
http://youtube.com/watch?v=wAGtdY18SGY&feature=related
Reverse Wrist Curl
http://youtube.com/watch?v=1c8aiFqKel8
All four of these feel really good when you do them slowly with proper form. There are other wrist, forearm and bicep excercises on youtube these are just some of the more common ones. I have a gym but honestly it has helped me a lot to have my own weight set at home. My barbell set has 300 lbs of weight and was purchased on sale for $120 at the sports authority here. I also have two dumbbell handles that accept plates and a preacher curl bar these were fairly cheap at the accursed walmart. To top it off I bought a big workout mat to save the carpet and turned my living room into my gym at home.