Defining Breakover
Breakover is probably the most talked about portion of equine hoof movement.
“Breakover” itself is the moment the toe lifts the ground.
The "breakover phase" begins when the heel lifts off the ground and ends when the toe leaves the ground.
Several factors influence where the point of breakover is on each individual horse.
The most important one is toe length.
Studies have shown that for every centimeter (3/8") of excessive toe length, approximately 110 pounds of additional pressure are placed upon the navicular bone by the deep digital flexor tendon. (Weller, 2016)
This means that the longer the toe, the more stress is placed on the navicular bone, the distal navicular ligament, and the navicular bursa.
How does it work
Breakover occurs with every single step a horse takes. For the horse to bring the hoof up and onto the toe, several things must happen:
1) The deep digital flexor muscles pull on the deep digital flexor tendon.
2) The deep digital flexor tendon runs underneath the navicular bone, acting like a fulcrum, and pulls on the coffin bone inside the hoof.
3) The coffin bone is attached to the hoof wall via the “laminae”. Once the deep digital flexor tendon pulls on the coffin bone, the heels lift off the ground.
4) The hoof rolls onto the toe and leaves the ground.
Factors Influencing Breakover
Conformation
Lameness
Foot balance
Frequency or infrequency of proper hoof care
Any appliance placed on the hoof by a hoof care professional
Rider influence or interference
Conformation
A variety of conformation defects will cause a horse to be heavy on the forehand, creating a delay in breakover.
Some examples are:
Horses built downhill with the hind end higher than the withers
Horses standing under in the front
Horses with long necks and large heads
Horses with short, thick necks that tie in low to the chest
Horses camped in front
Horses excessively straight behind
Horses with long pasterns
Horses with angular limb deformities (e.g. knocked-kneed) and/or rotational limb deformities (e.g. toed-out) will have a point of breakover that is not at the center of the toe.
For example:
A toed-out horse will breakover on the medial (inside) toe quarter. This is what causes toed-out horses to "wing-in" in movement.
A bow-legged (carpus varus) conformation is often accompanied by a toed-in rotational deformity. Toed-in horses will breakover on the lateral toe quarter. This is what causes toed-in horses to "wing-out" (also called "paddling") in movement.
Lameness
Mechanical lameness of the front limbs (e.g., bad knees, suspensory ligament injuries, problems with flexor tendons, etc) can delay or change breakover. Any lameness issues in the hind end of a horse will cause the horse to take weight off the back legs and transfer it to the front, which will also change breakover.
Foot Balance
In a well-proportioned, well-trimmed hoof, the length of the heels to the widest part of the foot should be equal to the length of the widest part of the foot to the toe. Excessive toe length will cause a delay in breakover.
The yellow dot is the point of breakover. You can see how much the point of breakover moved after the trim, the pink dot is the hoof’s “center of rotation”. The center of rotation always remains constant.
IMPORTANT: Increasing heel height does NOT lead to improved or quicker breakover. Because of the mechanics of the weightbearing structures in the back of the leg, when the heels are raised, the pastern drops. This dropping of the pastern angle increases the degree of movement required for breakover.
Please read our article “Understanding HoofPastern Angle” for a deeper dive on this topic.
Frequency (Or Infrequency) of Hoofcare
Most horse’s feet grow “forward”, creating more toe length. The longer the toe, the more delayed the breakover will be, adding additional stress on the navicular bone.
Horses should be maintained on a 5 to 8-week trimming schedule.
Shoes and Other Appliances
There are a variety of different appliances available for easing and increasing breakover, but one type does not fit all horses or all horses’ needs. For instance, a rocker toe shoe is rockered from the first nail hole, across the toe, to the second nail hole.
If the horse does not breakover in that area, then a rocker toe shoe would not help that particular horse. Many horses with rotational limb deformities, such as toed-in or toed-out, do not breakover at the center of the toe. Another application would be of more benefit to these horses.
Rider Influence or Interference
A delay in breakover can be caused by riders who:
Are too large for the horse they are riding
Allow the horse to get heavy on the forehand
Do not properly engage the horse’s back end
Pastern Length
A horse with long pasterns will have a foot that tends to grow forward, increasing toe length at a faster rate than in a “normal” pasterned horse. The toe doesn’t actually grow faster: the mechanical effects of the majority of weight bearing being behind the foot will cause the toe to “shoot out”. This will delay breakover and increase the amount of movement the horse will need to perform to bring the foot onto the toe.
WARNING!
Breakover is like medicine: it has to be just right, more is not better.
Increasing breakover past a balanced foot will cause issues: if breakover occurs to soon, the horse’s muscles won’t be prepared for it. This creates incoordination in movement and may adversely affect the impact phase of the foot striking the ground.
Increasing or modifying breakover is not a cure-all for gait abnormalities or other issues you may be experiencing with your horse’s quality of movement.
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