Slanted

 

Slanted stirrups have been around for a long time. The English saddle company Stubben has had them for over a hundred years.

The premise is very simple. In a traditional stirrup, when you turn the fender 90° to the horse, the outside of the stirrup is raised. This places your foot at about a 30° angle to the horse, misaligning the bones in your knee and ankle. The outside of my slanted stirrup is longer than the inside, so when you turn that fender, the stirrup is parallel to the ground, relieving the pressure and straightening your knees and ankles. So simple, but so effective. I make them in a lot of types.