Instead of a longer article, I went for one article per structure.
Here are the others:

• Sole
• Frog & Collateral Grooves
• White Line
• Bars
• Heels & Heel Bulb
• Coronary Band & Periople Skin

WALLS : EXTERNAL + INTERNAL

A healthy looking wall with minimal flaring.

The wall is what we see at 1st glance. On healthy feet, it should be close to equal width all around the foot and the wall at the toe (dorsal wall) should be parallel to the pastern. It should be smooth, with minimal growth rings and parallel tubules. It is actually composed of 2 layers: the external and the internal walls.

External wall: it is relatively hard, yet flexible, and pigmented if the hoof is not white. It is composed of a very large number of tubules, growing from the coronet band. It provides protection for the internal structures and regulates moisture. It also has an important action in stocking and releasing energy during the horse’s movements and plays a major role in propulsion. A healthy and balanced foot should display an even and smooth texture, without growth rings, cracks or deviations.

  • Flare where wall bends
  • Crack + growth ring
Unhealthy looking walls with major issues. Flaring, dietary problems creating huge rings, dry wall, tubules separating forming a massive crack.
Here are two hind legs with major hoof capsule (hoof wall) distortion: heavy medial (internal side of the foot) flare – lateral (external) hoof wall almost too upright. On this horse, it comes from impressive amount of arthritis in both fetlocks, hocks, gaskin and hips. 15 yo reformed jumper.

Internal wall: it is not pigmented, so usually white (a more solid white than a white foot’s external wall, that would look more translucent compared to the internal wall). It also originates from the coronary groove. In unhealthy feet, it can be so thin that it appears almost inexistent.

It is more supple and flexible than the external wall due to more moisture (slightly different composition) and protects the internal structures from shocks and vibrations. It also shares weight bearing function (with the outer sole).

  • White internal wall
  • Whiter internal wall
Notice the difference between internal and external walls. Left picture: black foot so external wall is black, internal is white – Right picture: white foot, so white external wall, but notice how “whiter” the internal wall looks.
  • Compromised
  • Non-existent
Compromised to non-existent internal hoof wall.
Take note of all the details you observe: here we see discoloration on a black foot, probably due to excess pressure at the coronary band when this white bit was being produced.