The thing about the 45 degree leg press is that it sacrifices a much larger footprint for higher absolute loading potential. However, even for the 45 degree leg press, there's not much use loading it past the point where the horizontal leg press stops. Additionally, it's easier to get into and load for a theoretical elderly or disabled trainee: they can get into and load it unassisted, where they might be incapable of operating a 45 degree machine in their own.
The loading can be done as incrementally as you have change plates: most models have a tension knob that increases the weight in increments of 2.5/5 pounds, and the knob can accommodate 2.5/1.25 pound plates.
The one scenario where a 45 degree press might be preferable is if the leg press is being used for a very obese trainee whose bulk prevents them from squatting to depth, but who is still capable of developing a lot of leg pressing strength. They might have to load it up to the 300 pound mark before they are physically able to squat to depth. But this seems like an remote possibility.
There is nearly a 100% chance that the doctor you meet with will recommend surgery, and in this case, I have to agree. There are a couple findings with this that are extremely troubling, and the longterm ramifications of not being treated are relatively severe.
For one, root tears almost always have to be addressed, and I have never seen a surgeon opt to not intervene when there is peripheral subluxation of the torn root attachment. This is a massive, massive problem long term. You also have a lot of cartilage loss on the medial femoral condyle, which given an assumption that you are relatively young, this will probably be best treated with one of a couple of procedures to try and preserve that surface for a while (chondroplasty, microfracture, etc).
To your actual question, though, you should continue to squat and deadlift. I'd caution against dynamic exercises until you get seen by ortho. A loaded squat will be relatively secure, even with the root tear because that compression on the joint will actually stabilize the tear.
You are going to have to make some choices, long term, though, brother.
Just a quick follow-up after meeting with the doc. He said he was willing to send me to PT but basically indicated that surgery is required. Due to the location of the meniscus tear (near the bone), the meniscus is not really functioning. Hence why any running, cutting, jumping, twisting is going to cause pain. So without surgery, the meniscus will wear out. He said PT can strengthen the area, but it wasn't clear to me how that would help. And I didn't understand why that would be better than squatting and deadlifting which I think would make the area stronger than with PT type exercises. He said it's ok to squat/deadlift/whatever as long as there isn't any sharp pain. Perhaps power cleans aren't a good idea but I didn't ask. He said that if I don't fix it with surgery, then I'm probably looking at a knee replacement in 5 years as opposed to 15. Hmm, I didn't realize I might ever need a knee replacement. I'm not sure what in the MRI indicated that would be the case. Maybe the thinning cartilage.
It seems like trying PT would be a waste of time so I'm just going to work the squats/deadlifts up, see how it feels. And seek some other opinions. I wonder where the state of stem cell research is tho..
Thanks for response; much appreciated.
The ortho didn't mention treatment for the cartilage loss, but I will look into that. Perhaps that's why he mentioned timelines for knee replacement (I'll need one in 15 years if surgery is done rather than 5). Makes me wonder if the other knee is in the same condition.
I was curious: what's the cause of such cartilage loss? Running, playing sports? Is this seen in weightlifters? I'm thinking it's perhaps time to cease activities that can cause such loss (like perhaps baseball).
Honestly, it is seen in course of life. We see a somewhat protective effect against degeneration in people who train consistently, whether it be weightlifting or running. Traumatic injuries (ACL tears and the like) accelerate degeneration. I’ll be perfectly frank with you, ceasing activities (which is more than likely going to be excessively broad) out of fear your knee may hurt is a particularly shitty idea. There are about a billion bodily functions that require physical activity to maintain their functionality for optimal health. 15 years to a knee replacement then 20-25 years with the newer joint prostheses gives you the better part of forty years of good function and the ability to participate in life. This idea of saving your joints by taking it easy is one of the most pervasive and damaging myths in modern life.