I would respectfully disagree with kayamedic on a few points. The new school of though is definitely NOT to do anything for four months, physical therapy should not create swelling, and physical therapy does not cause adhesions (actually the opposite of that). I am a Doctor of Physical Therapy, working in a rural clinic with a largely older population, and I usually have 2-3 knee replacement patients on my caseload.
I have heard statements like these before from a few orthopedic surgeons, and in each case they were from older surgeons near retirement. The new school of thought actually focuses on more movement and therapy initiated right after surgery. It used to be have surgery, wait a couple weeks, then start therapy. Then it shifted to start therapy after the 7-10 day follow-up. Now the surgeons in our region coming out of fellowships are referring patients to start therapy within a day or two of going home, which is usually the day after surgery. The research regarding physical therapy and knee replacements supports starting movement and range of motion exercises soon after surgery. From my experience, the patients that start therapy sooner tend to achieve full range of motion more quickly and with less discomfort than those that wait. (You do need to be careful the first 7-10 days post-op, the knee is still very “irritable” in that time frame, and it is easy to overdo it and increase swelling and pain. Think “uncomfortable, not painful”)
Physical Therapy (and any other activity) CAN cause inflammation and excessive pain, but it shouldn’t. Unfortunately there are some bad apples in every profession, so I don’t doubt there have been therapists that push too hard too fast. All activity, therapy included, should avoid inflammation. You will be uncomfortable with range of motion and stretching, but it shouldn’t be painful. And there is a difference. A good therapist will help you understand the difference and realize how far you can safely push it. If you are having pain, you will most likely also have swelling and inflammation, which will slow down the healing process. But it is possible, and sometimes necessary, to push ROM and strengthening to a point where it is uncomfortable, without causing inflammation.
The most current research regarding physical therapy after knee replacements is finding that the more strength you have after the surgery, the better you will be doing one year after surgery. More specifically, the more quad strength, with vastus medialis oblique being the muscle usually referenced. A good functional reference is this: continue with your strengthening until you can go down stairs with good control and proper knee alignment, with enough strength that you don’t need to use a handrail. That ensures you have good eccentric strength in the quads, which takes more strength and control than concentric exercises.
Sorry, that may have gotten a little too long! Good luck with your surgery, and feel free to contact me if you need need anything more specific.