I've had three knee surgeries. If your issue is a medial collateral ligament sprain, as in less than 50% of it is torn, it will heal on its own without surgery but it can be a very slow recovery. If it's a meniscus tear, the problem often isn't the tear itself but the loose material floating around gets caught in the joint and makes for a locked, balky, buckling knee--no one's idea of fun. Surgery can fix that.
All cortisone does is quickly reduce the inflammation and associated pain and allows you with the proper exercises to regain some lost range of motion. The problem with cortisone is it's temporary...in six weeks or so without strengthening your upper quad and hamstrings to take the load off the knee, you'll likely be back where you started. In other words, if you want to see if you can avoid surgery, get thyself to the gym, beginning with non-weighed movements (stationary biking, band stretching and non-weighted leg extensions are good) and slowly add light weight over many weeks.
If, however, you're partial to physical therapy just know that the PT's job is to get to the point where you can actually begin your rehab.
Unless you really know what you're doing, stay away from squats. Most people squat Olympic style, in which your knees move forward and your hips back putting far too much tension on the knee. If you know how to do sumo power lifting squats, where there's no pressure on your knees only your glutes and hips, ultimately that's the best way to gain strength once you've rehabbed for a while. But if all that's gibberish to you, don't squat.
And finally, you might want to wear a sleeve on your knee to give it some stability. Rehband makes the best by far. If you check out their site
http://www.rehband.com, the 3mm one probably is suitable--the thicker ones are more for power lifters.
