Well what you do would likely depend on why the stifle is clicking. It could just be air in the joint, or the ligament popping with each step. If it is the ligament getting caught on the joint, your equine veterinarian may do radio-graphs to determine how bad it is and if the stifle begins to catch or lock they may need to sever the ligament. However in most cases there is nothing to be done. It should be noted though that most horses with a clicking sound in any joint is likely to develop Arthritis fairly early in life or relatively quickly after you notice the clicking sound. You may want to ask your vet about a joint supplement or some other way to keep the horse comfortable if this does occur.
The stifle on a horse is the equivalent of a human knee.
A horse's stifle is equal to the knee of a human.
The noun stifle is the rear 'knee joint' of a horse.
knee
The stifle is the femoro-tibial joint, which in humans is commonly called the knee.
The knee.
The stifle of a horse is anatomically equivalent to the knee of a human - it is a hinge joint consisting of the distal femur, proximal tibia, proximal fibula and the patella (kneecap).
The stifle is a joint in the hind leg that works much like a human knee. It's found at the front of the hind leg near the flank.
Stifle (Stifle Joint) Underlying the stifle area is the stifle joint formed between the large hip bone (femur) which is equivalent to our thigh bone and the tibia, equivalent to our shin bone. The stifle joint somewhat resembles a human knee.
The snaffle is a type of bit. A similar word is stifle, which is a hind leg joint in the horse.
The animal with a second thigh called a gaskin is a horse. The gaskin is the part of the hind leg in a horse that extends from above the hock to the stifle joint. It is an important muscle group for the horse's movement and strength.
The location is a bit hard to describe. To see a diagram of where the stifle is located, follow this link. http://img.quamut.com/chart/7321/34_horse_anatomy.jpg (look at the tail end of the URL, it says horse_anatomy.jpg This is how you know it's a legitimate link to a picture of a horse and not a bad site.) Hope this helps! Happy trails!