Ankle Bone Instability
There is a very common condition where the ankle bone loses its normal stability and alignment on the heel bone. This one pathologic condition is responsible for the majority of atraumatic orthopedic deformities of the body. This condition is known by many different names, but the best and the easiest name is the one that we’ve given it – ankle bone instability.
What is ankle bone instability?
This is an orthopedic deformity where the ankle bone has lost its normal stability on the heel bone. In other words, it is a partial dislocation between the ankle and heel bone. The joint surfaces between the ankle and heel bones are misaligned. When there is no weight on the foot, the joint surfaces of the ankle bone are aligned on the heel bone. When weight is placed on the foot, the joint surfaces of the ankle bone are partially dislocated on the heel bone.
2. Presence of an arch with no weight on the foot and lowering of the arch when standing. A lowering of arch is not always present.
3. Look at the area below and in front of the inner ankle bone. There may be a noticeable inward bulging on the ankle bone which is from the ankle bone partially dislocating inward on the heel bone. This is not always present, but when it is, it is another supportive finding of an ankle bone dislocation.
4. Look at the lower leg compared with the front of the foot. A stable ankle bone will have an aligned hindfoot. A misaligned ankle bone will turn inward.
5. Look at the inner arch. Is an arch present with no weight and it lowers when weight is placed on the foot? Remember, a lowering of the arch is not always present.
6. Look at the alignment of the back of the heel. The back of the heel should be aligned with the lower leg. When the ankle bone partially dislocates inward, the heel will turn outward. This is a form of compensation. This finding is not always present, but you can pretty much assume that the ankle bone will be partially dislocated when you see this happening.
7. Look for the “too many toes” sign. This is when more than the 5th toe is seen when looking from the back to the outer front of the foot.
Radiographic confirmation will be needed to accurately diagnose the partial dislocation of the ankle bone. The only way to determine if ankle bone instability is present is to take 2 sets of x-rays. One set is taken while the patient is standing with full weight on the foot. This is called “relaxed” or uncorrected stance. The second set is taken with the ankle bone repositioned on the heel. This is a corrected stance position.
Ankle bone dislocation can be diagnosed with only the relaxed stance x-rays. Just because the ankle bone is partially dislocated on the heel does not prove that the ankle bone can be repositioned on the heel bone. The motion to realign the foot may be occurring between the ankle and arch bone, rather than the ankle and heel bones.
Side / Lateral View X-ray:
1. Ankle Bone Angle/Declination
This shows that there is an abnormal angulation in the sagittal plane of the ankle bone. The angle of the ankle bone should be more horizontal.
The forces from the ankle bone are going to push the arch bone and midfoot bones downward.
The image below shows the difference between a stable and aligned ankle bone compared to a partially dislocated ankle bone.
The source of the excessive forces acting on the foot is caused by the partially dislocated/dislocating ankle bone.
2. Sinus Tarsi Space – Wide open or partially closed?
The sinus tarsi space between the ankle and heel bones should be open. There are no specific measurements to document a normal or not normal sinus tarsi space.
Top-Bottom View X-ray:
1. Ankle Bone Angle – Top-Bottom X-ray
The bisection of the ankle bone should be within or to the outside of the 1st metatarsal bone. Ankle bone misalignment can be diagnosed if the bisection falls to the inside of the 1st metatarsal bone. This can be used to document the partial dislocation of the ankle bone.
To diagnose ankle bone instability, a 2nd x-ray has to be taken for the ankle bone to be placed back into its normal alignment on the heel bone.
Even though the bisection of the ankle bone did not move back to the normal alignment, it still documents flexibility. This has to be confirmed on both the top-bottom and side views of the foot.
Ankle Joint X-ray
Many different x-rays can be taken of the foot. The two most common have already be shown above. There is another that could also show an aligned or partially dislocated ankle bone.
Weightbearing Fluoroscopic Videos:
The best way to diagnose ankle bone instability is to take weight-bearing fluoroscopic videos. This clearly shows an unstable or partially dislocating ankle bone.
Is ankle bone instability the same as a misaligned ankle bone?
HyProCure can fix ankle bone instability, but if there is no motion between the ankle and heel bones and the sinus tarsi space cannot be re-opened, then HyProCure is not an option. For that reason, it is very important to make sure your ankle bone condition is flexible or fixed. Also, if you wait too long to have your ankle bone instability fixed with HyProCure it will become fixed and more aggressive surgery will be required.
What is the medical diagnosis of Ankle Bone Instability?
The orthopedic name given to this disease entity is recurrent talotarsal joint dislocation.
Recurrent: It happens over and over, again and again.
Talotarsal: The ankle bone is referred to as the talus or talo-. Tarsal refers to the hindfoot bones, heel, and arch bones.
Joint: This is an area between two bones where motion occurs. The joint is made of the 2 surfaces between the bones.
Dislocation: This is a generic term that is used to describe a situation where the joint surface of one bone is no longer aligned with the joint surface of the opposite bone. There can be traumatic dislocations that happen after an unexpected force acts between the two bones. Atraumatic dislocation occurs when there is no trauma. There can be a complete dislocation when the two joint surfaces are not in contact at all. There is no overlap between the two surfaces. There is also a partial dislocation when there is still a partial overlap between the two surfaces. That is the situation with ankle bone instability.
Why is ankle bone instability a “bad” thing?
The ankle-heel joint is the foundation joint of the body. Think about it, the entire weight of the body is positioned on the ankle bone. It has to be balanced on the heel bone.
Below is a video that shows someone standing on their feet and putting the ankle bone through the range of motion. When the ankle bone loses its stability on the heel bone, this creates a faulty foot foundation. You can clearly see the difference between a stable ankle bone and a partially dislocating ankle bone. When the ankle bone partially dislocates on the heel bone, this drops the foundation to the body. The leg bone will become lowered because it sits on the heel bone. This creates a “functional” leg length difference in height between the two legs.
Excessive ankle bone motion will lead to an excessive motion to knees, hips, and back. Sometimes the knees are strong enough to withstand the twisting, then the excessive motion will occur within the hips. A misaligned ankle bone will lead to a tilt to the pelvis. Pelvic tilt places a strain on the column of the bones that form the spine. Ligaments within the spine are strained which leads to muscle contraction in an attempt to straighten the spine. The shoulders and neck can even be affected.
The bones, joints, ligaments, muscles, tendons, and nerves within the foot are also negatively affected. Excessive strain will be placed on the inner column of foot bones. It is possible to eventually develop pain in other parts of the foot.
If ankle bone instability is such a bad thing, why don’t I have any pain between the ankle and heel bones?
The majority of people with ankle bone instability will never experience any pain between the ankle and heel bones. Pain occurs at a site of tissue damage. The nerves have been activated to send a signal that something is wrong. Pain is never normal. In non-traumatic orthopedic diseases, there will be the cause/etiology and the effect/symptom. For every symptom there is an underlying cause. The symptom is the secondary effect of the primary deformity.
Think about an ingrown toenail. A piece of the toenail is growing into the flesh on the side of the toe. The pressure of the nail digging into the skin causes the soft tissues to react. It becomes painful, swollen, red, and even infected. You can soak your toe, take pain medications, treat the infection, but it will continue to get worse until you cut out the ingrown nail. You have to reduce/eliminate the source-cause of the condition. If the focus is only aimed at the symptoms, without addressing the underlying cause, then the symptoms will continue. You might be able to decrease the symptoms temporarily, but they will come back if the ingrown toenail is left alone.
This is what we see in the treatment of many orthopedic deformities. The majority of “treatments” are aimed at the symptoms while the underlying cause is left ignored. Think about it. We need to find the reason why the tissues within our feet, knees, hips, and back have become destroyed. There has to be an excessive force acting on those parts of our body. Where is the source of excessive force? It starts with ankle bone instability.