horse walking for hours around field

Question
I have three old ponies 2 mares and one gelding. The mare will walk behind the gelding making him walk constantly, not letting him eat.  they have lived together for 18 years.  the last year she has started this behaviour.  The gelding has arthritis in his back leg.  The mare has acquired sweet itch.  But I have bought a sweet itch rug that covers her entire body.  Why is she doing this?  Is it to keep him mobile sensing this will helphis arthritis. Or is she trying to rid him out of the herd (But she isn't biting or kicking him and her ears aren't back. Some times the other mare will walk with them, but she gets fed up after an hour and wants to graze! I have fenced him off some times for a rest, but he's always happy to rejoin them.

Answer
Hello Regina,

First, thank you for your great question. There are many things to take into consideration before giving you my honest opinion. Therefore, I am going to ask you a couple of questions that will help me better to understand exactly to what your dealing with. First, is this mare older or younger then your gelding? How much roaming space is provided for your horses? Have you checked this mare for a possible blindness issue? How does this mare react when you place your gelding apart from her? Is the mare in question your Alpha mare? (leader of the herd) After these questions are answered, I will be able to determine what is going on. Also, I will address some great ideas and remedies for the arthritis & sweet itch that may be of some help to you. Look forward to those answers.