Karen, saw your post and decided to sign up so I could reply, so this my first post also. I cycled the Camino last year. I started in St Jean, biked to Logrono, over night bus from there to Leon, then biked from there to Santiago. It was amazing. I travelled in the last week of July and had no trouble finding a bed in the Albergues. The walkers path can get very busy during the day so I spent a lot of time on the main road that runs parallel to the path. I met a couple (husband and wife) from Holland, they had cycled form their front door and biked the entire route. I cycled alongside the husband for an hour and he explained that his wife had a battery powered bike that meant she could still cycle but at a faster speed. It may help your knees.
If I can help with anything please ask. I am considering the norde route in July this year, just need to convince my wife she thinks I should do it!