So here are the essentials, as far as I am concerned:
- Landing: hooves should land heel first on a flat, level surface. This is clearly visible in a healthy hoof and becomes more pronounced when the horse walks down a slope. Conversely a toe first landing is normal when a horse walks uphill but is a sign of potential caudal hoof pain on a flat surface.
- front limb hooves should load evenly (medio-laterally) when walking on a flat, level surface
- hind limb hooves will normally land laterally (this can usually only be seen in slowed down footage)
- Surfaces: a healthy hoof has good proprioception so stride length will normally adjust slightly as a horse crosses different surfaces (there is a reason dressage is not done on concrete). However, a horse should not look pottery or restricted on a hard surface.
- Gait: horses will, of course, alter their movement in response to pain, or its removal - a heel first landing can change to toe first, and vice versa. Equally, stride length can increase as hooves load in a more balanced way or develop a better ability to shock absorb. It can be useful (and interesting) to film your horse's movement regularly to monitor changes and give you reference points.