elliptical and water running

I went swimming in LA a couple of weeks ago. I tried the water running that runliarun suggested. The scary result was that even the 20min of water running bother my left knee. I'm not sure what that means. This week I tried elliptical machine for 30min. This is the second time I've exercised since the marathon. I know quite pathetic:). If I'm not training, I'm a sloth bug:). My knee felt like it swelled up after the ellpitical machine. I'm going to see my sports massage therapists in a week or so. I'll see what he says. I've been using a heating pad to speed up the healing. I'll see how it goes. I might try to go running with my running club on Saturday. Maybe an easy 5-6 miles. If it feels off, I'll stop.