I cannot comment on what you can expect in the UK, but we often fly into LAX. At this airport you can expect that there will be a wheelchair waiting for you at the door of your airplane. The wheelchair person will take you through passport control and baggage claim and customs. Your spouse will be allowed to move with you, and you will not be required to wait in any lines.
Once you have your baggage, the wheelchair person will assist your husband to load your luggage on a cart, or he will obtain a person with a cart to help your husband. This person will also expect a tip, but it is well worth the service.
These two individuals will then ask you where you need to go. If you need to rent a car they will take you to that area and help you on to the shuttle bus. If you need to take a shuttle bus to a hotel, they will take you to the shuttle bus area and help you. They will generally take you wherever you need to go. I have never been dumped at baggage, and my husband has never been required to manage our baggage on his own.
Overall, every experience we have had at LAX has been excellent, and I would expect you would have not difficulty there.
I do not know if your hip and knee surgery is recent. Knee surgery takes about 6 months of difficult PT, but hip surgery is much easier. I traveled to Istanbul from Florida just three weeks after hip surgery. It was not the most pleasant experience I have ever had, but it really was not that difficult. Perhaps by January you will be feeling a bit better.