I have had two partial knee replacements; one over 5 years ago, the other last February. The first one gave me no problems and little pain. I expected the second one to be the same, but I had a lot of problems.
One problem I experienced was pain from having the slightest pressure. It did go away, but it took a while. I think it was likely caused by swelling pressing on the nerves around my knee - and also may be the result of having nerves cut, then being very sensitive while they regenerate. I, too, had pain radiating downward, and had bad leg and foot cramps that woke me up at night. As for swelling in your foot, that could come from the swelling in your knee draining down into your foot due to gravity. Any swelling will make the swollen area tender, even if it's not the injured area. You will probably experience swelling in your knee for a while. Do you keep it elevated at all? You should try to elevate it - above your heart when possible (like when you sleep) - that should help the swelling.
You haven't had much recovery time yet. You have probably read accounts of patients doing very well right after the surgery. Every case is different (as I said in the beginning - my knees were different)! I know how frustrating the pain is. No one understood how I felt, were tired of hearing about it, and so I eventually stopped telling them. I would sometimes have such pain that the only think I could do was cry - hard (alone, of course), which actually seemed to help a little. My doctor was absolutely no help. He had done his job. Every time I went to him, either for him to check the knee, or for pain, he'd take x-rays and tell me everything was fine. Physical therapy didn't help, either. I think the best remedy for me was time. I now participate in my martial arts training again, more fully than before my surgery. I, too had the most hopeless feeling, and no one understood. No one really can understand unless they've experienced it, too. Before surgery you have such high hopes - the pain will be gone, you'll be able to resume your activities. I was so excited. Then I was so disappointed - and depressed. But - take heart:
You WILL feel better. Your knee WILL stop hurting. It's been 10 months since my surgery, and I am doing so much better. I used to cry from the pain and thought that it would never get better. Believe me, it will. Do whatever you can to keep moving, because that will help - it will help reduce the swelling and strengthen your muscles, which is essential. If you do not strengthen your muscles (especially the quadriceps right above the knee) then your joint has to bear all the weight and that adds to the pain. Ask your doctor or physical therapist for simple exercises to do at home. Walking is essential, even if it hurts. After any activity, ice it for 10-15 minutes (actually, a large bag of frozen peas is better because it conforms to the shape of your knee) keeping it elevated.
Keep your hopes up. It WILL get better. Give yourself some time. Don't expect to be better all at once. Look back every so often and check yourself compared to one or two weeks before. You will see that you ARE getting better.
Forgot to add that I just turned 54!
I have had partial replacement 6 weeks ago and am also experiencing bad pain and the feeling of my leg giving way with a sharp pain. Your comments gave me hope as I was getting desperate thinking it would never improve. I am now going to give it more of a go and try to 'break through' the pain barriers. David
PKR Makoplasty 24 April 2015. Knee now gets very stiff with any use. Worse now than 6 weeks ago. Tests show no infection or blood clot but knee remains hot and stiff even though off PT for 2 weeks. Good ROM but don't do PT now due to stiffness! Been walking and biking for many, many, years (age 77) but can't now due to knee stiffness. Anyone similar problems/solutions?