From: lbm@avs.com (Linda B. Merims)
Subject: Re: Chronic Sporadic Lameness Revisited
Organization: Advanced Visual Systems Inc.
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Date: Tue, 13 Oct 1992 23:52:33 GMT
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Well, I just happen to have my copy of Dr. James R. Rooney's
"The Lame Horse" on my desk.  Rooney was a lameness expert
at Cornell.  I believe he is now at the University of Kentucky,
and has a reputation one of the world's experts on lameness.
The book has a second printing date of 1975, and so might
be a little out of date.  I know Rooney's ideas on club feet
and contracted tendons have changed substantially recently.  It is a good
book, though it has the usual failing of "a little about a lot
of things," with nothing treated in real depth.

He characterizes ringbone as follows (illustrated with photos
and radiographs):
                               || <----base of cannon 
                               // <----long pastern
                              //   
                             /    <----short pastern
                          /_/     <----coffin bone

"Ringbone" is new bone formation around a joint.

Low ringbone  --  new bone formation in the coffin joint.
                  He says it is "rarely a sole reason for
                  lameness" and then says he won't deal with it here.

High ringbone --  new bone formation in the short and long pasterns

  Articulate  --  an arthrosis in the pastern joint between the
                  short and long pasterns caused by:
                  - overdorsiflexion of the pastern joint (bent too far
                    back)
                  - He cites two instances:
                      - race horses, hunters, working Quarter Horses
                      - a genetic trait in a certain breed of Norweigian
                        draft horses.  In these horses, the ridge
                        on the short pastern joint surface that helps
                        resist overdorsiflexion was underdeveloped.  So
                        the long pastern rotated too far down and damaged
                        the cartilage and caused the arthrosis.

 Non-articulate --  bony growth on the outsides of the bones (not the
                    cartilage surface).  He says this can occur in
                    many places on these two bones, because it is
                    basically new bone forming as a result of a ligament
                    tear where the ligament attacheds to the bones.  There are
                    lots of ligaments, and thus lots of potential sites.
                  - He cites two instances
                    - heels trimmed too low, which by a complicated
                      series of interactions causes ringbone at the
                      point of attachment of the straight sesamoid
                      ligament, and may eventually lead to articulate
                      ringbone.
                    - feet trimmed unevenly laterally, where "uneven"
                      means not trimmed the way the horse naturally
                      lands flat, vs "even" the way some farriers
                      try to trim both sides of the hoof the same length,
                      no matter how crooked the horse naturally is.
                      - because the hoof lands on one side before the
                        other, the hoof "rocks" laterally, which can
                        strain and tear the ligaments on the opposite
                        side of the fetlock.  I'm not sure, but I think
                        he says the ringbone will occur lower down on
                        the side with the long hoof wall as the hoof
                        suddenly snaps level.
                      - this often occurs in draft horses because of
                        "their big platter feet" are often trimmed
                        unbalanced.

He says there's no cure.  He recommends a good farrier.  In the absence
of that, he recommends pulling the shoes and letting the feet wear
down where and how they naturally want to, and then going along with
that with a rasp.   (It has been my observation that many farriers attempt
to "carve" a correct hoof on a horse, and ignore how it is actually built.)

His last paragraph is "Once ringbone is with you, it will always be
with you, but good trimming and/or shoeing will often add some years
to the working life of the animal."

My filly had high ringbone as a secondary effect of her club foot.
(The ringbone was the least of her troubles.)  It was quite
noticeably and predictably affected by how she was trimmed.  I
believe non-articulate is less serious than articulate.

Linda B. Merims