Facts: 		
Swollen right hind fetlock: Shows some abnormal condition in right hind fetlock
Foal lame on right hind, refusing to use it: painful enough to not use
Mare might have stepped on foalÕs leg: possible trauma
Thoroughbred filly, 2w bay: very young filly
Nursing normally: disease not causing depression, not likely systemic
Current vaccines and de-worming (mare): not likely infectious
Foal hasnÕt been vaccinated or de-wormed: Not time yet
Temp of foal: 101.8: normal temperature
Pulse 60: normal 
Respiratory rate 52: normal 
BA, all systems except musculoskeletal normal: localized injury
Toe touching lame on right rear leg: painful joint
Soft tissue swelling (pitting edema) starting 12cm proximal to fetlock, 
extending just 
distal to it.: some disease process, inflammation etc to cause soft tissue 
swelling
Foal resents palpation of area: painful
No foreign body in foot: eliminates foreign body possibility
Foal doesnÕt resent hoof testers: pain not localized in hoof
Manipulation of fetlock: more lame, wonÕt use at all: worse on manipulation, 
worse with 
movÕt
No instability or crepitance on palpation: early problem
Part of small herd: may have had access to trauma by other horses