I had dodgy knees & cured them with a Tracer Theraplay semi Recumbent. Which gave me confidence to go for a conventional trike the Pashley. This was too bulky for the car so bought a Claud Butler Stratos 20inch folding bike, but this was too twitchy for my 76 year old knees so I'm going back to a semi recumbent maybe this one, anyone had one?
Mission Semi Recumbent Trike Tricycle Cycle | eBay