Lump - anyone know what it could be?

[Kit]

My old horse has a lump (sort of hard and flattish but noticeable and about the size of when you join your thumb and forefinger together) between her fetlock joint and coronet band on the front of her front leg. She has always been a bit lame on that leg. She's retired. But I have noticed the same sort of bump on my friend's horse who has been lame slightly for some time. Could it be a similar problem I am thinking as her horse has never been diagnosed. This bump is new on her horse. What could these bumps be and could they be what is causing them to be lame?

[InstigatorKate]

High ringbone? aka osteoarthritis of the intra-phalangeal joint.

http://en.wikipedia.org/wiki/Ringbone

And yes, it is a common cause of lameness in older horses.

[Kit]

Thanks very much!!