Calf Muscle – Equinus

Calf Muscle – Equinus

There is a condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should. This will cause an imbalance of forces acting within the foot and lead to other painful conditions. Our goal is to find out why the calf muscles tighten and what is the best form of treatment.

Calf Muscle – Equinus condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should

Equinus – What is it?

Calf Muscle – Equinus condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should

Equinus (pronounced “e-ka-wine-us”) is a condition where the calf muscles and/or the Achilles tendon is tighter than it should be.

This could be either a physical shortening where the tendon is shorter or it is a functional shortening. When you hear the word equinus – that refers to a horse -equine. In this condition, the person’s foot functions like a horse’s hoof where the heel does not touch the ground. That is the real form of equinus. When walking, the heel does not touch the ground. That is something you are born with; you either have it or don’t.

The most common form of calf muscle-Achilles tendon tightening is referred to as acquired or developed over time. The longer you live, the more likely you will develop it and it will get progressively worse.

Why does it happen?

Nearly all physicians who specialize in foot and ankle disorders can detect this condition but very few can tell you the why. It will be revealed to you here. This is an extremely important question. If you don’t know why it happened/developed in the first place, then how can you fix it or make it go away?

The congenital equinus is the one you are born with. This is seen as a toe-walking child. The muscle-tendon complex is shorter than it should be which prevents the heel from touching the ground when walking. It could also be a form of compensation for other conditions within the foot.

The more complex and mysterious form of equinus is the acquired form. Why would the calf muscles and Achilles tendon shrink over decades? This seems very unusual but there are other situations in the calf-foot where the muscle-tendon tightens. The tissues of the body, bones, ligaments, and tendons will react if an excessive strain is placed on the tissue(s). The stability of the bones and joints of the body is monitored by strain sensors that are located in the ligament.

Calf Muscle – Equinus condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should

When there is a normal amount of joint motion, there will also be a normal amount of strain on the ligaments surrounding that joint.

If the joint loses its stability and partially dislocates, that leads to an excessive strain on the ligament(s), and the nerve strain sensors are activated. That warning signal is sent to the spine; the spine reacts by sending another signal to the muscle(s) associated with that joint. That electrical signal forces the muscle to contract in an attempt to stabilize the joint. This forced muscle contraction is only effective to a certain point and is not meant to occur during one’s lifetime, rather it should be only for an occasional event.

Now, back to the calf muscle-Achilles tendon complex. The calf muscles are the most powerful ankle bone stabilizers. They are given the task to provide stability when excessive ankle bone motion is present. Another function of the calf muscle is to lift our heel off the ground and propel the foot forward during walking.

What happens when the ankle bone loses its normal stability on the heel bone? The network of ligaments that attach to the ankle bone become over-stretched. The ligaments send the warning signal to the spine which in turn sends a signal to the calf muscles to contract to stabilize the ankle bone. The only problem is that this is not a one-off event. This occurs with every step taken, thousands of times per day. The calf muscles are working over-time, first contracting to stabilize the ankle bone, then to contract further to lift the heel and propel the foot forward.

Why is acquired equinus a “bad” thing?

The shortening/contraction of the calf muscles and the Achilles tendon will have negative effects on the knee and foot. One of the calf muscles, called gastrocnemius, is attached to the thigh bone, femur. Excessive contraction of the muscle can negatively affect the knee joint. Excessive pull on the back bottom portion of the heel can eventually alter the angle of the heel bone. The back of the heel is pulled upwards and the front of the heel falls downward. This further complicates the ankle bone dislocation.

The combination of tight calf muscles and lower than normal heel bone angle leads to increased forces acting on the midfoot and also the forefoot.

This progressively gets worse and is the main cause of a severe condition in feet that have lost their normal nerve function. A condition especially associated with long-standing diabetics called Charcot’s foot occurs when a boiling point of forces is reached and the foot bones basically explode, fracturing into many pieces. The structure of the foot goes from bad to worse.

Calf Muscle – Equinus condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should

What is the best form of treatment?

When treating any disease, it is important to eliminate/reduce the underlying cause.

Failure to do so will result in a continuation of the symptoms related to that disease. In this case, the symptom is the excessive contracture of the calf muscle. Any attempt to stretch-out or surgically weaken the Achilles tendon or muscle will fail long-term because the underlying cause is still present.

The reason why the muscle-tendon complex is excessively contracted is due to ankle bone instability. The first place to start is to stabilize the ankle bone on the heel bone. Imagine what good it is to perform calf stretches 3 times per day for 10 minutes each time, when all day, after thousands of steps per day, the ankle bone partially dislocates on the heel bone causing the spine to send signals to the calf muscles to contract in an attempt to bring stability to the ankle bone. Calf stretches do not address the underlying etiology.

There are many bulky splints that patients are told to buy, or their insurance carriers are forced to buy, that are never going to prevent or solve the underlying cause of acquired equinus. The calf muscles will naturally relax when you are sitting and watching tv. The issue is when you are up walking around. The “equinus brace” can only be used at a time when it really does no good. There is no science to show that a brace can fix the equinus. How could it? The ankle bone instability is still present and the spine is still sending a signal to the calf.

Every day people are getting their Achilles tendons “lengthened” or the attachment between one of the calf muscle-tendon attachments cut to weaken the contraction of the calf muscles on the heel.


The effectiveness of this option is also called into question, especially when the underlying cause of ankle bone instability is left untreated. One of the main issues in the diagnosis of equinus is that it is completely subjective. In other words, there is really no way to diagnose the presence, absence, or degree of the contracture. Ankle bone instability is objectively diagnosed with standing x-rays. There are clear and measurable findings that are consistently seen and reproducible from physician to physician. The same is not true with the diagnosis of equinus.

The test that is used most commonly is to have the person sitting or lying down. The examiner lifts the leg and pushes against the forefoot to see how much extension there is between the foot and the leg. A second part of the test has the person bend their knee; this eliminates the possible effect of the one calf muscle that is attached to the thigh bone. Failure to get more than 5 to 10 degrees of flexion is considered a positive test or you have a tighter than normal calf muscle-tendon complex.

That test has many flaws and is not reproducible from one examiner to another.

But the main reason why it is not a good test is that the muscle and tendon are getting stretched, the sensors within the tendon and muscle are activated, and the spine will cause the muscle to contract to counter the stretch. This is a counter-intuitive test. There are 2 better methods. The first is simply to hold out a leg and point your-toes-to-your-nose. This eliminates the forced strain on the muscles and tendons. If you can get your foot above a 90-degree bend, then you don’t have an equinus. The other method is to stand with your knee tight, not bent, and lean forward. This will naturally, rather than unnaturally, test if an equinus is present.

Something that is not routinely discussed or told to people who have a weakening/lengthening procedure is that there is a chance the contracture can come back after surgery. This finding is reported in scientific studies. It always seems to be a mystery why the tightness reoccurs. Now you know the reason why – ankle bone instability is still present.

The best form of treatment is to first identify if there is a structural or functional issue with a shorter than normal or excessively contracted calf muscle. The second point is to see if the ankle bone is stable and aligned or partially dislocated. If the ankle bone is partially dislocated, then the first step is to realign and maintain the stability of the ankle bone on the heel bone. The best method, when indicated, is the insertion of HyProCure into the sinus tarsi. This is the only option that can be shown to maintain the alignment and stability of the ankle bone while still allowing a normal range of motion.

Once the ankle bone is stabilized, it is possible that no other forms of treatment are necessary.

There are situations where the combination of HyProCure along with calf muscle or Achilles tendon lengthening is necessary. Only your foot surgeon will be able to discuss that with you. Just remember, there is no evidence that lengthening the Achilles or cutting the muscle will realign and stabilize the ankle bone.

Calf Muscle – Equinus condition where the calf muscles and the strong Achilles tendon become tighter and/or shorter than they should

What happens if you don’t treat equinus?

Failure to eliminate the cause of equinus will allow the calf muscle and tendon to contract and shorten. This will continue to progressively pull the heel bone upward and allow the head of the ankle bone to push down on the front of the heel. This creates tremendous strain to the mid- and forefoot and eventually, a severe destructive joint disease will destroy the bones of the foot. Early treatment and preventative measures are essential to maintain the integrity and function of the bones of the foot.

Just remember, this will never go away; it will only get worse. This is a symptom of ankle bone instability and there will be many other symptoms that will appear. You may not experience pain to your calf or Achilles tendon but the symptoms can appear as heel pain, pain to the ball of your foot, and even knee pain. It is better to internally stabilize the ankle bone to prevent the multitude of secondary symptoms.

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