What are the possibilities?...foot pain

[short strided]

My horse has had recurring severe lamness in his left hind over the past 6 weeks. The initial diagnosis from farrier and vet was bruising in the frog, as he had a positive reaction to the hoof testers in that area and radiographs were clean. They don't think it's an abscess. The vet has been unable to get a pain response from flexion.

He will randomly appear sound and then go back to walking on his toe. We blocked it Saturday and it is definitely fetlock or below.

I am going to send him to LSU for an MRI and possible bone scan, but I am interested in hearing what everyone thinks about this. My vet, at one time, suspected a DDFT injury within the hoof capsule, but now he seems kind of stumped.

[Peggy]

Did the vet do incremental blocks? IOW, do you know how it blocked to a "heel" block and so on?

Based on a fortunately limited set of data, it seems that people who do both the bone scan (scintigraphy) and the MRI get a more satisfactory diagnosis than those who do the MRI alone. Note that satisfactory = you figure out what's going on, not that you like it!