Curbs

[GypsyTashi <GypsyTashi@aol.com>]

Has anyone had experience with curbs on the rear legs?  1 1/2 years ago my
mare developed one; gave her about a year off, started her back slowly and she
was doing great in competitive rides.  Started in our first 50 with no
problems.  At the second vet check her CRI was 10/9 but lame on the third
stride of the trot out, heat at the curb site.  Any suggestions or help
understanding curbs greatly appreciated.