I'm sorry to have to welcome you to our community - noone would want to be here in an ideal world but if you have PMR you'll get plenty of advice from people who live with PMR and have done so for some time.
First of all here is a link to another post at the top of this forum:
https://patient.info/forums/discuss/pmr-gca-and-other-website-addresses-35316
In it you will find links to a support site from the northeast support group with medically-approved info and stories from PMR patients past and present. I encourage you to read it and possibly to join the other forum at forumup which is far more active than this one and where we work more like a real support group - laughs and whinges included! There is also a link to a paper from a group in Bristol, aimed at GPs but mostly easy enough to be read by most patients, certainly something ALL GPs and many rheumatologists should have pressed in their hands and be encouraged to read.
This group in Bristol gives 15mg for 6 weeks, 12.5mg for 6 weeks and then 10mg for A YEAR and by doing this finds they have a much lower rate of flares at 2 years (20% as opposed to 60%). It has been said in the medical literature in the past that the most common cause of flares is reducing too far and too fast and tat the worst thing to do is yoyo the dose to control a flare - going slowly and avoiding one is far better longterm.
Noone will be able to cut down on their pred dose successfully until the inflammation is under control - a patient diagnosed and treated quickly might be fine after a month at 15mg - but in most cases they will struggle. After over 5 years with PMR (too young, no raised blood values) I was given 15mg for 2 weeks, cut to 10mg for 2 weeks when I started to feel bad again and then to 5mg - where I managed but was in pain most of the time. On stopping the pred after 6 weeks I was worse than at the start. After that I have struggled to get below 9mg/day - and every time I was encouraged to go below that level I had a flare. I have now succeeded by reducing 1mg at a time (and that is since 15mg) and not even doing that overnight - at higher doses I did alternate days old/new, 15/14/15/14 for eg, for at least a week before going to the new dose. Since 10mg it takes me about 6 weeks, working on one day at the new dose, 6 days old, one day new, 5 days old and so on until I get to alternate days. Then I increase the number of days at the new dose between the old dose in the opposite way until I get to 6 days new, 1 day old. Then I reckon I'm ready to fly on the new dose every day. I wait a few weeks before starting all over again for the next 1mg reduction. By doing that I have reached 6mg with no problems. Even at that rate my GP here in Italy is saying slowly, slowly!
Tony - your wife probably IS suffering because of doing the zumba I'm afraid. Even physiotherapy in PMR is associated with risks if it is too aggressive (good physios know that, others don't) and trying to be back to normal just because you are on pred is being far too optimistic. Many of us who work with the forums are constantly amazed at statement like "you'll be back to normal as soon as you are on pred", "you can do as much exercise as possible, it's good for you" - and from people who should jolly well know better.
If she is going back to 15mg to control the symptoms she should go to the GP and make sure she has enough pred to stay there for at least a month. Take a copy of the Bristol group paper I gave you the link for and get the GP to read it - there is actually no reason why your GP shouldn't manage the PMR treatment as you can see from that paper. The PMR isn't cured by the pred - it allows you to manage it by controlling the inflammation that leads to the pain and stiffness. One day, sooner if she is lucky, later if she is not, the autoimmune disease which is the underlying cause will go into remission and she will be able to SLOWLY get off the pred - you always keep trying but always with a tiny dose because the pain due to a flare and the pain due to taking away the pred are similar. By creeping down you are less likely to cause either - you might find you are fine at 10 but not at 7.5 - you might be fine at 8mg but not 7.5. Half a mg can make a big difference!
Nearly all of us know the frustration Tony - most of us were fit and active until PMR struck. But you have to manage what you have - and when you are reducing in particular it is a good idea to clear the decks and have a few duvet days until you know you feel good at the new dose - I have to say I don't need that with my technique because the difference is so small. I wouldn't/couldn't do zumba even now! The effect of PMR is to make the muscles need far far longer to recover from any exercise, even walking, especially if there is an upward slope so that little session of zumba feels like a marathon to her muscles and they are letting her know. Rest is key in managing PMR - especially in the early stages. If she wants to do exercise then aqua classes would be better at first - but still take it easy. Many people mistake the wellbeing of pred for being cured - you're not. And if the inflammation is still there - you will have problems even reducing from 20 to 15. A lady on this forum a couple of years ago couldn't get below 20mg until she tried this very slow version - and then managed down below 10mg before needing a hip replacement which interfered a bit! Rule of thumb: never more than 10% of the current dose, anything over 1.5mg at a time has the potential to lead to trouble.
As you mention swollen joints - is the dx of PMR certain? Did the 15mg pred achieve a large effect within 24-48 hours? It is not unusual for PMR to be confused with LORA (late onset rheumatoid arthritis) but some patients with PMR do also have swollen joints though it is less common than the shoulder and hip stiffness and pain.
This is quite enough for a start - read the Bristol group paper and what you find on the northeast support site and come back with any questions you still have. We'll try to answer them one by one. Also - where do you live? There may be a real live support group within reach. And I do recommend your wife comes and chats to us on the northeast PMR and GCA support group forum at forum up because there are loads of encouraging photos there - this week one lady, who like me has had an interesting 4 years of PMR and has been reducing the way I have, walked round Virginia Water with photographic evidence. This time last year we could barely manage a few hundred yards - you do improve!
Eileen