I started the road to getting back in to shape on September 4th. My left knee had given me problems in the past and it became worse after I started lifting.

I went to a sports medicine doctor and he basically said I should not be doing anything that puts pressure on the knee caps. Squats and deadlifts are out.

Using the sled to do an incline leg press is OK and calf raises are Ok.

What can I do that does not involve a squat-like movement to work my hamstring?

I forgot to add the info the doctor gave me was that a squat like lift puts 3.5 times the weight in pressure on the knee caps and that climbing stairs puts 7.5 times the weight in pressure on the knee caps.

I had never heard this before and found it very interesting.

I presume that lunges, including side lunges, are also unacceptable?

You say that you can't do squats. Can you do squat holds? Get yourself a large fitness ball. Back up against a wall, put the ball against the wall behind you at about the middle of your back. Balancing with your back against the ball, squat and hold the squat position for at least 30 seconds before coming back up. Your hamstrings will definitely feel the burn but holding in place won't put the same stress on your kneecaps that going up and down does.

What about step ups? Step up onto a platform, keeping one leg fixed in place on the platform while the other steps up and down. Hold weights if you'd like. Variant: Instead of bringing your second leg on to the platform, step up so that you are suspended on one leg with the second leg raised in the air (makes it a balance/core exercise as well).

Bodyweight excercises...you'll never overdo it becasue it's only you, it's never too much weight, and you only do what you can, if 3 reps is it then 3 reps is it, try for four tomorrow.

or low impact martial arts (internal styles), tai chi, bagua, some schools of wing chun.

I have been advised to not do anything that involves a step up. The squat holds sounds like something I am going to try. I use to do those in high school in my weights and conditioning class. That produced a lot of moaning and groaning, so you know they were good for you.

As for my body weight...I am currently clocking in at 258 (down from 276 on September 2nd), so it may be a little excessive to do anything with my own weight.

The martial arts thing has always interested me, but with two small children, making the time fo rth egym and a couple of classes is just not possible right now.

Thanks for the advice, everyone.

That sucks about the stairs. I do stairs a couple times a week and it's a great workout but I often do feel pain in my knees afterward. I guess that's only going to get worse as I get older if I continue, right?

The good news, Christian, is that the more you lose weight, the easier any body-weight-bearing exercise is going to become. That has been the best part of weight loss for me; I almost look forward to push ups and squats nowadays!