Originally Posted by Horseman56
I'm not clear on the relationship you are suggesting between stringhalt (fixation of the patella in the hind limb) and equine laryngeal function.
Do you understand what stringhalt is?
Mark and OP, stringhalt is a myoclonic spasm. This means a jerking spasm of the muscles. It is not upward fixation of the patella, which is another affliction that is often mistaken for stringhalt. They look similar but have different causes, treatments and outcomes.
To the OP: you are right, no one is completely sure what causes stringhalt. The theory is that it is a type of peripheral neuropathy or myopathy meaning there is something wrong with either nerves or muscles. It is usually limited to the hindquarters and you are right, there are some theories that a toxin can be to blame. Roaring on the otherhand is caused by damage to the recurrent laryngeal nerve which lives in the throat (and passes around the heart) and when damaged it fails to appropriately open the larynx causing the roaring noise. Choke is due to a blockage of the esophagus. So these three are not really related at all except to say that if you have a toxin affecting nerves it could cause choking and a strange gait that could be mistaken for either stringhalt or upward fixation of the patella (but again, these two are different things which can sometimes be mistaken for one another)