Hi Cate, Excellent advice above! Here is my story and it may not work for everyone, but it shows that with a lot of help from various parts of the medical profession and a lot of self discipline, one can make their own Camino work.
I have osteoarthritis in my knees and feet - bone on bone. An orthopedist recommended knee replacement four years ago. Instead, with help from my Primary Care Physician, Physical Therapists, acupuncture, anti-inflammatory supplements and working out at the YMCA (core, leg and upper body strengthening), I have - so far- avoided the surgery - and the bone on bone is not quite so severe - per comparative x-rays.
Last Sept/Oct/Nov I went from St Jean to Santiago - walking about half the time and taking bus, taxi, and accepting a couple of rides from Spaniards. All of these "options" had their own wonderful experiences! I used trekking poles - mostly for up and down terrain (and chasing flies along one section of the Meseta!) - and when I walk the Camino again in the fall, I will have my trusty "assistants"!! To help further, I took tylenol / paracetamol and used arnica every morning and evening.
We are all unique, so what worked for me one time may not work for others -- and may not work for me a second time. But I'm sure going to give it a good try - and hopefully will be able to walk all the way - even if I have to keep my distance to about 7 - 10 miles a day with rest days interspersed. I will also buy anti-imflams along the way so I have them, but won't have to carry a bunch that adds to the weight of the pack. And speaking of the pack -- I have already purchased my new one - 28 liters that will weigh about 12 lbs (with water and snacks) - less than what I carried last fall.
BTW, I will turn 70 in the fall.
Buen Camino Cate!!
Terry