Is there a facility near you where a nuclear scan could be performed? (Here
in the Us, most vet schools have tha capability, and some private practices
as well.) It is an excellent tool for pinpointing obscure lamenesses. A soft
tissue phase can be done (within certain limits; in your case, where the
limb flexion is positive you could focus on that area), followed by bone
scintigraphy. Lesions which are not obvious on radiographs are often quite
well-defined with this method.
--CMNewell, DVM
"The expression in a horse's eye is like a blessing on a good man's house."
--Sayied iben-el Rabil, quoting the Prophet