What is rotation of the coffin bone (P3) in horses?

We can imagine the hoof laminae as a kind of velcro that keeps P3 attached to the inner surface of the hoof wall.

On the opposite side we have the deep digital flexor tendon (DDFT), inserted on the solar surface of P3, in its caudal or posterior region. This tendon generates constant tension on the bone, pulling on it with every step, every stride and even simply because the horse is standing.

In other words, there is constant tension between the laminae and the deep digital flexor tendon. As long as both forces remain balanced, this relationship keeps P3 in a natural, balanced position inside the hoof.

Any term including the suffix “-itis” refers to an inflammatory process. So when we talk about laminitis, we are talking about an inflammatory process affecting the laminar tissue of the hoof.

When the laminae become inflamed, due to any of the causes explained in other sections, their structure and their ability to withstand mechanical forces are compromised.

And if the laminae weaken, the battle against the deep digital flexor tendon is no longer balanced.

The laminae, our “laminar velcro”, can no longer properly withstand the traction exerted by the DDFT. This attachment begins to deform, elongate and lose its ability to hold P3 in position, and displacement of the third phalanx inside the hoof may occur.

In certain cases, this displacement presents as rotation of P3.

When this process occurs, several events are happening at the same time.

On one hand, the laminae that have been damaged and lost their ability to hold P3 in position can also suffer a significant alteration of their blood supply and nutrient delivery. When a tissue significantly loses its blood supply, the risk of tissue damage and necrosis increases.

On the other hand, when P3 changes position, the relationship between the third phalanx and the solar corium — the tissue responsible for producing the sole — also changes.

In all laminitis cases with P3 displacement, the tip of the third phalanx exerts excessive pressure on the solar corium. This pressure can compromise local blood circulation and limit the corium's ability to produce a sole thick enough to protect the bone.

This can create a vicious circle: less sole production leaves less protection between P3 and the ground, increasing the vulnerability of the internal hoof structures and the risk of bone changes and bone remodelling.

When this process persists over time, it means laminar damage already exists and, in some cases, damage to bone structures.

That is why it is so important to act quickly and correctly at the first signs of laminitis.

The aim of treatment must be to control the inflammatory and mechanical process, create suitable conditions to restore circulation and reduce the forces keeping P3 displaced.

In this context, hoof management and laminitis horseshoes can play a fundamental role within an individualised treatment protocol. The goal should not simply be to “fit a shoe”, but to modify the forces acting inside the hoof, reduce the tension exerted by the deep digital flexor tendon and provide the conditions needed to support recovery of the laminar structures.

One of the key objectives is to enable the horse to develop a sole thick enough to protect P3, while supporting the recovery of the damaged structures.