Squat. I have seen 65 year old men with total knee replacements squat semi heavy... Unless you have a VERY VALID reason, go learn how to squat heavy. Hell I do not think there is one TBH, one of my old mates squatted 2.5xBW with no ACL.

Here is a gift for you...

http://www.leangains.com/2011/09/fuckarounditis.html

If your knee is fucked up enough that you "TRULY" cannot squat, time for a visit to the ortho doc! But ask yourself if you are just being a whiny bitch or are you honestly hurt? Cheers for being blunt today!

Do some stretching, mobility exercises, foam rolling and myofacial release to see if it helps. If you get better, start squatting.

Break out the bicycle and have fun, that's all.

BTW, is the leg-press weight thing standardized these days? I remember when you could brag about lifting a ton or more, but the weights were on an inclined ramp, nothing calibrated correctly, didn't mean diddly squat. Has that changed?

Regarding the knee, we need a lot more information regarding the type of pain you're experiencing. Where about is the pain? What type of activities make it hurt? Does it hurt more going up or down stairs? Does the pain go away once warmed up? Is it dull or sharp pain?

What does your exercise regime look like? You obviously run and do leg presses, what else? What sort of miles do you do each week? Do you do any other leg exercises beside presses?

The potential problem with leg presses is that it's a very quad dominant exercise, it doesn't do a lot in recruiting the hamstrings or the glutes - so the issue can be if you're only doing leg presses you may develop muscle imbalances, and when these occur in your leg and then pull unevenly on the knee, it may hinder the knee tracking correctly.

If you squat with correct form and below parallel, you equal out the forces on the knee by recruiting the quads, hamstrings, glutes and hips in a balanced manner.

Mark Rippetoe's book, Starting Strength, is the best text I have read on perfecting squat form, though a few sessions with a decent coach will get you squatting well in no time, as the instant feed back of form corrections makes the process much faster and is worth the investment.

Of course your issues may not stem from imbalanced muscle issues, it could have some to do with running form, poor flexibility / mobility. When you run, do you heel strike?

Go to a physical therapist and get a diagnosis, then never go back! Just google it and find how to rehab online.

I wouldn't just jump into squats with a knee injury. If you're not distributing properly (which you aren't) that's bound to cause further damage.

Whatever your injury, the one consistent goal of rehab is to regain symmetry of strength. So you'll be isolating the injured leg and building the necessary muscle group to support the injury. Do this before any squats, lunges, plyometrics, anything really.

Stay away from the leg press, it forces your knees in an angle that's not good for you, and it doesn't translate into real world motion very well.

I'm totally in agreement with the other posts here who say squats are good. Start with low weight and work your way up avoiding all knee pain. You'll also want to make sure you're doing full range of motion (if you have to ask if you're going low enough in the squat, the answer is "no"), that's the best thing for your knees, stopping at our around parallel is where the stress is the biggest on the joint.

First, I would recommend some rest if the marathon has been completed recently. Second, I would recommend never running a marathon again. Third, I would recommend getting off the leg press thingy and squat. Start with bodyweight squats and see if your knee is fine with that. Then, progress to squats with the bar on your back, in front of you in the rack position, overhead with a barbell, holding a kettlebell or dumbbell in front of you and any other way you can think of to squat down. Leg presses are of very little benefit as they do not allow your core to get stronger. All human movement requires core stability and strength. Work your center and you will be better off.

I've been doing cardio like treadmill, stairclimber and bike. This doesn't hurt but my knees while doing it but they are sore afterwards.

trx force training

How do you like the water? I've got a meniscus tear & floating debris in my knee (getting it scoped is on my to-do list) and I'm enjoying the pool. A water aerobics class, in fact, and I've found it's not nearly so geeky/old lady as it sounds. I find it comparable to doing pilates when I've got the "good" instructor. And when I get distracted and hyperextend my bad knee, I don't end up yelping like I would on land.

Or yep, a bike. Or pilates! In my experience, a really good pilates instructor beats the pants off of most physical therapists. They're pickier and just as sophisticated. Reformer work has been great for my knee issues.