I was asked by several people to put up Dawn's very good x-rays so they could see what a good set looks like, as people tend to put up x-rays where the horse has a problem. So, here they are. We elected not to remove her shoes, and the x-rays still came out very well.
The first two shots are lateral shots - taken from the side. These show the arrangement of the bones and any gross abnormalities may show up here. From the bottom up, that's the coffin, pedal or P3 bone, with the navicular bone nestled in behind; then the small pastern or P2 bone; then the large pastern or P1 bone, and at the very top the bottom of the cannon bone with the sesamoid nestled behind. We were mostly interested in the P1/P2 and P2/P3 joints, as well as the navicular area, since that was where she had shown some soreness on the right front in the flexion tests. We did both front feet to be sure we had a good idea of what her "normal" was and to be able to compare the two front feet. These shots, and the medial shots that follow, were taken with her standing with her front feet up on small wooden blocks - this is very awkward but she was very cooperative. (She's due for a trim, so her toes are a little bit long and the shoe is shifted a bit to front as well.)
Right front lateral:
Left front lateral:
The next set of shots are from the back, showing the bony column of the foot and lower leg. The things that look like round holes in the P3 bone at the bottom are blood vessels. The metal pin is in the picture to help with orientation. You will notice in these shots that Dawn doesn't stand with her lower bones straight under her cannon bone - there's a bit of a deviation, which is more pronounced in the right leg. She clearly also tends to weight the outside edges of her feet a bit more than the inside, as there's a bit more hoof growth there. This is the reason she paddles - she tends to swing her feet a bit to the outside, more with the right, particularly at the trot. But all of these things are completely normal for her - they're how she's built. Every horse is different and has its own normal - the question is can they compensate for any deviations and do the deviations cause them any problems.
I've enlarged the two major joints so you can see them more clearly. What the vet is looking for her is good joint spaces and also whether there is any sign of osteoarthritis, which often tends to show up at the lateral edges of the joints first. Dawn has just the slightest bit of joint remodeling - the tiniest bit of "lipping" - on the outside edge of her P1/P2 joint in the right front, but it's so slight as to be very hard to see in these shots.
Right front medial (from the rear):
Right front medial - close-up of P1/P2 (large pastern/small pastern) joint:
Here's an extreme close-up of the right (outside) edge of the P1/P2 joint - the little tiny point to the outside of the top right edge of the lower P2 bone is the small amount of bone remodeling I was talking about - it's hard to see:
Right front medial - close-up of P2/P3 (small pastern/coffin) joint:
Left front medial:
Left front medial - close-up of P1/P2 joint:
Left front medial - close-up of P2/P3 joint:
Now for some shots from the bottom - these were taken with the foot being shot standing on a flat box that holds the film or digital receiver. The solar shots are taken with her foot directly under her. The dark V that starts towards the toe and extends on either side as far back as the P2/P3 joint (just behind the heels of the shoe) is the shadow of the frog - the shading at the bottom of the P2 bone isn't a problem, just a shadow.
Right front solar:
Left front solar:
Now, on the the navicular shots. These are hard to take - the horse has to stand on the flat wooden box with the foot stretched under the body - this gets the pastern bones more out of the way so with luck the navicular bone can be seen. My vet says these shots are unusually clear - even with shoes off the navicular bones can be hard to image. The navicular bone is the one with the flat edge with the little bump-out that runs across the middle of the foot. The light edge is the bone, and the darker center is the interior of the bone, with its blood supply. What the vet is looking for here is a clean sharp dark to light edge and a consistent quality in the interior - basically no signs of deterioration or rough edges that could indicate poor blood supply or edges that could irritate or tear tendons and ligaments. Dawn's shots were very good.
Right front navicular skyline:
Left front navicular skyline:
So there you go - I'm no vet and hope I got the explanations straight!