Shall I let mum with Alzheimer's have a knee replacement?

Thank you all so much for your answers. Your answers have helped me come to the decision FOR NOW to put the replacement on hold. I have a gut feeling her whole condition will deteriorate if it goes ahead.
I told her husband today I was not happy for her to have the op and thankfully he didn't insist she had it when I pointed out all potential pitfalls. When mum had steroid injection in her knee it wasn't exray guided, although it helped with the swelling it did not help with the pain.
I can always weigh the situation up further down the line, but for now it's not going to happen. Thank you all x

This is not a decision to be made immediately. You can say no right now but decide to go ahead later if the disability becomes too severe for her to tolerate.
As far as the PT is concerned for rehab, it will probably be recommended that she go to a rehab facility for the first few weeks so by the time she comes home she will be walking with a walker or cane.
Physical therapy for a knee replacement involves active movement of the limb not having someone move it a round for you. Yes the PT will assist and support the leg but the patient moves it themselves. very little time is spent in bed after the first day. The patient will be up in a chair and will use a commode at the bedside or be assisted to the bathroom. There will be a catheter in for the first couple of days but is quickly removed to prevent a UTI,
Spinal anesthesia with sedation means that the patient will be as unaware as if they were under general anesthetic but will wake up quickly and have fewer side effects.
As far as the confusion of being in a hospital setting is concerned plan to spend as much time as possible with her and even spend some nights in the beginning.
You now the old saying."When the pain of what you are doing becomes greater than the pain of what you have to do" then you take action.
Only you know your Mum and what she can tolerate and how you will care for her at home which will almost certainly be your home. Just don't rush into anything. Expect it to take up to a year for function to return but once the pain of surgery is gone in a few weeks she will be comfortable

Let's proceed on the info you've given;
1. "Mom has moderate (approaching severe) Alzheimers disease."
2. "Step dad is finding it increasingly difficult to look after her."
3. "My mum would no way keep up any given exercises."
4. ..."(her) husband wouldn't adhere to any exercise advise."
5. "I'm inclined to object the op, I just have a bad feeling."

IMO, if your mum went ahead with the operation, she would (for sure) be living with you. Step dad ALREADY can't handle her. You would be solely responsible for her recuperation and recovery. Are you able (physically and mentally) to handle this? Can you move her leg (dead weight) and do exercise routines with her 4 times a day? Would you be able to quit your job or have a live in for her?

Was her steroid injection guided by Xray? Many times the doctor is "shooting in the dark" unless it's guided, to see where the medication is going. There are also the other treatments spoken of. I would exhaust all possibilities before sending her to surgery.

We also don't listen to that little voice inside. If you don't feel good about it, it may be for a reason. Try homeopathic remedies, ointments, braces, wraps, heat/cold packs, etc. and have the doc change or up the dose of pain medication until you can figure this out. Google Non-surgical treatments for osteoarthritis.

When my husband came out of the hospital after 1 month (severe pneumonia), he couldn't move at all. All of his muscles had weakened and gone limp. He couldn't sit up without support, couldn't roll over in bed, couldn't walk, couldn't eat by himself. He needed 24 hour care AND muscle strengthening exercises 4 times a day. I'm a nurse so I figured I could handle it, cook, clean, bathe, feed, transfer, exercises, etc.
OMG, I was exhausted. I was in my early 50's but I felt like I was 100! There was no one else to physically help me. After a week, (in tears) I begged my MIL to come to cook and lightly clean, thank God she did. Within 6 weeks (of daily PT at the house) hubby made a miraculous recovery. But it entailed an enormous amount of effort (on both our parts). He was great at doing the exercise routines but I remembered how I'd dread those times of day. He was in his late 40's at the time.

This is a HUGE responsibility for you and only you (unless there are others to help). I would wonder how much benefit will your mother get from her new knee if she's not willing (or able) to put forth the effort to exercise it.

Whatever you do, DON'T beat yourself up for the decision you make. You are weighing all the facts and trying to come to an informed decision. That's all anyone can ask of you. You obviously care a great deal for your mum and that's all that matters.

Angela I don't think speaking to her doctor on the phone is going to give you detailed enough answers. Is it not possible for you to accompany them to an outpatient appointment and ask for the anaesthetist and the orthopaedic surgeon to be there?

Our local hospital is officially "dementia-friendly." This means that on some wards the staff have had extra training in communicating with people with dementia; and they put blue flower stickers on the patients' notes so that everyone looks out for special needs. Or that's the idea anyway...

If your mother does want to go ahead, her care plan needs to include reassurance pre-op, during surgery if it's to be done with a spinal block, and post-op and in recovery. That means somebody being with her, and you need to discuss how that would be handled. In eye clinics for example, it'd be a member of the nursing team; but that's a much shorter procedure and besides they're much more used to treating dementia patients.

Is there some particular hurry to get this done? What sort of hospital would be doing the surgery, is it private or NHS or what?

Thank you all so much for your good advice. I work three 8.5 hour days a week, although I usually take mum for her med appointments, it was her husband who took her for this orthopaedic apt. He is eager for mum to have the op. I will phone her dr. this week to ask about a local anasthetic. My mum would no way keep up any given exercises, so it would be led to her husband and myself ( I have my mum 2 days a week), im sure her husband wouldnt adhere to any exercise advice. 
She would be very upset in a hospital environment.  I am inclined to object to the op,  I just have a bad feeling. But as someone said I may be depriving her of a pain free life (ending). I'm sure whatever I decide I will beat myself up and think it was the wrong answer. Thanks everyone.

Angela11, I remembered a couple years ago when my Dad was referred to an orthopedic doctor to see what could be done about his knee. The first thing the doctor spoke about was surgery, nothing else, and was even trying to schedule a time for surgery. I was relieved when my Dad kept saying "no", then he walked right past the scheduling desk and out the door :)

My Dad figured at 93 it would take him over a year of rehab which in itself would be painful, so why bother going through the surgery if he had only a year or two left in his life. Dad experimented with different pain relief ointments until he found a winner that worked great for him.

"She has moderate, I think approaching severe Alz. "

This makes your decision especially difficult. In your shoes, I would seek alternatives to surgery. All doctors are not created equal. My DH's injured shoulder was treated with a steroid injection, with no benefit. Then we went to a pain management physician and he used an X-ray guided steroid injection. It worked beautifully.
Blessings,
Jamie

Do ask about anesthesia, because it may not be general anesthesia. I just had both knees replaced, and my anesthesia was spinal with sedation. Much easier on the brain fog, and maybe better for a compromised senior. Most knees today are done using the spinal with sedation combo (and yes, the patient is completely unaware of the surgery being performed). I know general anesthesia can be a huge problem for patients who are already suffering Alzheimer's or dementia, because my FIL took a big step backward with his surgery, but don't know if this other option carries the same risks.

Freqflyer has a good idea. I just heard of this at a lunch date. Going under for the elderly is not good. It hastens the Dementia. Can ur Mom take instruction? Are u willing to follow up with exercises she will need to do. At a care meeting I had for Mom the therapist kept saying she had a hard time with Mom following her directions and I kept saying she has Dementia. I know you want to relieve her pain. Me, I am not a caregiver and I was innocent in what is involved. Without help, its a 24/7 job. As Mom gets worse, there will be incontinence. I had to clean up a lot of messes Mom made trying to do it herself. After 2 yrs I had to find an alternative. Someone on this forum made the statement her Mom was a senior and so was she. Thats the problem, in our sixties we are slowing down and losing strength and are expected to care for people who become dead weight. Sorry, at 5ft tall I know my limit.

Angela11, one option instead of knee replacement is implanted plastic cartilage for those with bone on bone knee issues. This type of replacement is fairly new but is having positive results. It's something you can ask your Mom's doctor.

All your fears are valid, but Mum's condition has ben adversely affected by the knee. Even if she never moves her leg these days it still gives her a lot of pain. Even if she is given enough narcotics to ease the pain the side effects will be undesirable long term.
The pain can be relieved with a knee replacement. She could be able to make a fully functional pain free recovery but it will require commitment from everyone in the family. PT can only go so far because of time limits. Even if she gets an hour every day there are still 23 hours when the family will have to encourage the exercises. Rehab will do a lot of this if it is a good facility.
As far as the anesthetic is concerned, many times these ointments are done with a spinal anesthetic and heavy sedation.. The patient is still completely unaware but the dangers of general anesthesia are avoided.
No way of predicting how the hospital stay will affect Mum's mental status.
it is commonly believed that most elderly will die within a year of a major joint replacement. is that true? I will let you know in ten months because i am 78 and just had a hip replacement. The estimate for recovery in 4-6 months is probably optimistic.I would expect it to take up to a year, but if recovery is complete it should be possible to take walks again but she may need to use a cane or walker.
The choice is between Mum being in pain for the rest of her life of taking the chance of undergoing surgery and becoming more functional. The longer she sits around the less she will be able to do for herself.

I so agree with Countrymouse! You have to weigh the pros and cons. I don't know her general health or how much physical exercise she is used to.

She will have to be cleared by her various providers, correct? Cardiology, PCP? They will communicate with each other to assess your mother's stability before even scheduling the procedure. Is she stable enough to tolerate the procedure? She will probably be on Coumadin for 28 days. Will she go to rehab afterwards! This is a must to get her moving. Or, begin physical therapy at home and quickly progress to out patient PT for optimal rehab.  Can she get to out patient physical therapy by the family 2x/wk ? Recovery can take up to 4-6 months at that age. Please ask her surgeon to place her in rehab post op for her to get the care she will need. 

Hard decision as it sounds If she's in fairly good health. But these surgeries with anesthesia really effect elderly patients adversely.

That's the huge elephant in the room, but in my experience with anesthesia and geriatrics, it needs to be discussed as anesthesia almost always will have an adverse effect on the senior as well. And loss of routine while she is in the hospital for the surgery will throw a monkey wrench in her routine. She needs rehab post op if possible.

If she is in good physical health and needs a knee replacement, I cannot make that decision for you. If it's successful it will greatly improve her quality of life with increasing mobility and no more knee pain for her. But she will have to work it, not you! She has to be committed to physical therapy. 

Best of luck to you and your family.

It depends on the quality of the hospital, the possibility of ensuring that your mother is accompanied at all times, and the skill of the rehabilitation team. Where would the surgery be done, is it a place you already have an established relationship with? What discussions have you had with her surgeon (and anaesthetist, just as importantly)?

Apart from further questions, my two main thoughts are "a chance to cut is a chance to cure" - the prize here would be a radical improvement in your mother's quality of life; but, secondly, that this is a bit of a "sh*t or bust" option. There are substantial risks. What could be done to pre-empt them?