M.P.
I have 2 close friends who have had knee replacements. One is a diabetic, has arthritis and has bi-polar disorder. I can share their experience.
Having some form of physical exercise using the knee everyday is important. I'm sure the physical therapist has given her exercises to do. Even just walking on level ground helps the healing to be faster and to relieve pain.
Also, her legs should not have any pressure on them when she's sitting in a chair. She should try putting a phone book or very low foot stool under her feet so that the backs of her legs are not pushing against the seat. I think, that at 1 month, she should still be sitting with her leg elevated for the most part. Put a pillow under the knee(s). Elevating both legs would be the most comfortable. Does she have a recliner or an upholstered chair with an ottoman?
Both of my friends wore a skirt or loose knee length shorts for 2-3 months after surgery. One is in her 60's and one in her 70's and they found appropriate looking garments. Now is a good time to find walking shorts or bermudas. Her incision and the area around it will be sensitive for some time to come. Bending the knee will cause long pants to pull on the knee.
The one who is a diabetic also had some neuropathy in her feet. She complained of pain in the leg with the new knee but not in her other leg. She didn't have any increase in the neuropathy. Both women said that they had intermittent prickly feeling in the leg after surgery. I've had several abdominal surgeries and I can tell you that the intermittent burning pain and the prickly sensations are an indication that the nerves are healing. It's a good thing.
However, surgery in one leg would not result in pain and prickly sensations in the other leg. Unless......she is tensing that leg in response to the pain in the other one. Also, if she did not use those muscles much before the surgery and is using them now because of favoring the leg with surgery and in doing physical therapy it would be expected that that leg would have pain and discomfort. Increasing the use of both thighs could result in them feeling tight and sore.
They feel swollen. Do they look swollen? Again, keeping the legs elevated might help that.
1 month is not a very long time after surgery. If she's not had other surgeries this is all a new experience. It does take time for the tissue and the nerves to heal. My abdominal scar still feels prickly from time to time and hurts a bit when I press on it and it's been over 10 years since my last surgery. If the doctor is not concerned I'd suggest that you find ways to help her relax.
Also, remind her that general anesthesia takes a lot out of you energy wise. She is still recovering from the anesthesia. She'll feel better in general in another month or two. I can vouch for the fact that it takes around a year to get totally over the anesthesia. The effects are subtle but there none the less. I was easily tired and discouraged for the first 2-3 months. My energy level gradually increased.
My friend with diabetes did not have difficulty with her diabetes after surgery. She did have serious trouble with depression. And she continues to have pain several years later because she refuses to walk or do other physical therapy exercises. She also has arthritis in her back which could be helped with exercise but she says it hurts too much to do it. She has taken prescription pain medication off and on as well as ibuprofen. Ibuprofen is an anti-inflammatory as well as a pain reliever which makes it a better choice then acetaminophen.
The other friend is happy and active. She alternates walking and swimming 5 days/week. Her sister-in-law is also doing well after knee replacement. She lives on a farm and has 2-3 teen children which has caused her to keep active. Both of them said that it took a year at least before they really felt better.
I recommend learning some ways to relax. I like to use guided imagery. I also use an electric blanket. The overall warmth eases my off and on joint pains. And if she can feel assured that she is progressing normally she'll have less symptoms. When we're unsure we pay too much attention to what is happening instead of relaxing, knowing that this is OK.
If you haven't gone to the doctor with her, I recommend that you do. You may hear his message differently than she does and you can reassure her.