What is Ankle Equinus?
Ankle equinus is a common issue that most people experience when they first visit a foot and ankle specialist. Around 96.5% of new foot or ankle patients are found to have it. This condition is identified by a decreased ability to flex the foot upward at the ankle joint. However, there is no agreed upon amount of loss in this upward movement, called dorsiflexion, that is used for a diagnosis.
The term “ankle equinus” can be used to refer to the position of the ankle, a walking pattern, or a foot deformity. When describing a walking pattern, ankle equinus refers to the downward flexing of the foot in both the standing and swinging phases of walking.
When it describes a foot deformity, ankle equinus results from over-tightening of a specific muscle group (the gastrocnemius-soleus complex) in the lower leg. This over-tightening leads to too much pull from the Achilles tendon where it attaches to the heel bone (the calcaneal tuberosity).
What Causes Ankle Equinus?
Ankle equinus is a condition where the foot’s upward bending movement, or dorsiflexion, is limited. This can happen because of bone limitations, issues with the nerves or muscles, or tightness in the calf muscle or nearby soft tissues. If you have severe or long-lasting arthritis, it could cause front-of-ankle joint pain and restrict movement, leading to this condition. Similarly, in people with nervous system and muscle disorders, like cerebral palsy, there could be excessive tightness in certain calf muscles leading to equinus.
This limitation of upward foot movement isn’t always because of nerve or muscle issues. According to a study by Feraru and colleagues, there are three other groups of causes for equinus:
1. Acquired: This means causes that happen after birth, including trauma, tumours, infection, burns, and compartment syndrome, a painful condition that occurs when pressure within the muscles builds to dangerous levels.
2. Congenital: These are causes that are present from birth, like Hemimelia which is the partial or total absence of a limb, Phocomelia, a condition where the arms or legs are extremely shortened or even absent, and stroke that happens in the womb.
3. Idiopathic: These are causes that we don’t exactly know why they happen. They include sensory integration issues and autism.
Risk Factors and Frequency for Ankle Equinus
Ankle equinus, often resulting from walking on toes, is not necessarily more common today due to either born-with or developed conditions. However, it is noticed more often in kids with mental health or development issues, with slightly more boys showing this behavior. In a study, 2% of typical developing 5.5-year-old kids were found toe walking, in contrast to 41% in those with mental health or developmental hurdles.
Signs and Symptoms of Ankle Equinus
Ankle equinus contracture is a condition that affects the mobility of the ankle. A physical examination is often enough to diagnose it, but a detailed medical history and complete physical examination are crucial to find out the root cause and create a proper treatment plan. Doctors need to specifically check for any past or present neuromuscular or neuropsychiatric disorders, injuries, or diabetes. They also need to understand a patient’s activity level.
Parents usually first notice this condition in their children when they see their kids walking on their toes or having toes that point downwards. The most common reasons kids get ankle equinus deformity are cerebral palsy and idiopathic toe walking, which means walking on your toes without a known reason. Kids with a history of cerebral palsy, autism, or neuropsychiatric disorders might be at a higher risk. It’s also more common in kids with neuropsychiatric diagnoses. Any past injury to the foot or ankle can also result in this condition. After an injury, patients often need to stay still for a while, and if their foot is in a position where the toes are pointing downwards, this can result in ankle equinus deformity.
Diabetes patients might develop this condition due to diabetic neuropathy. This can cause damage to the nerves in the lower legs and feet, which can then lead to muscle weakness in the area around the outer ankle that helps lift the foot. This creates an imbalance between the muscles at the back and front of the ankle, resulting in equinus deformity.
When examining a patient with ankle equinus, doctors pay particular attention to:
- Inspection: They look for any deformities from the hips to toes, any situation that could contribute to ankle contracture.
- Hair loss or changes in the skin might be signs of diabetic neuropathy, autonomic dysreflexia, or lack of blood flow to an area.
- Palpation: They check the pulses for signs of blood flow problems.
- They perform tests if sensation is reduced.
- Limb length: Doctors confirm if both legs are the same length by measuring each one from the hip bone to the inner ankle bone.
- Range of motion: They check the moving range of the knee, ankle, and subtalar (below the ankle) joints.
In addition, a Silverskiold test is performed to check the flexibility of the lower leg muscles. If the ankle’s dorsiflexion (ability to move your foot upwards) is limited when the knee is bent, it shows that the ‘heel cord’ (Achilles tendon/soleus complex) is too tight. If the same happens when the knee is straight, it’s due to the tension in the whole gastrocnemius-soleus complex, which comprises major muscles in your calf.
Usually, if a patient has less than 5° of upward foot movement with a straight knee and more than 10° with a bent knee, it indicates a tight gastrocnemius muscle. And if they have less than 10° of upward foot movement with a bent knee, it means the entire gastrocnemius-soleus complex is tight. These are sometimes known as gastrocnemius equinus and gastrocnemius-soleus equinus, respectively.
Testing for Ankle Equinus
If your child is suspected of having idiopathic toe walking — a condition where a child walks on their toes without any known cause — imaging, like x-rays or scans, is generally not needed. However, if your child’s tight heel cord, called an equinus contracture, isn’t getting better with initial treatment, an x-ray might be considered to get a detailed picture of what’s going on. Luckily, further imaging beyond basic x-rays is rarely needed.
In cases where it’s suspected that the bones in the foot or ankle are contributing to the problem, an x-ray of the ankle would be ordered to take a closer look at the bones and identify any potential issues. If there’s a concern about one of your child’s legs being longer than the other, a full-body x-ray can be used to measure and compare the length of each leg.
If there’s evidence of a developmental delay or unusual findings during a neurologic exam, a magnetic resonance imaging (MRI) — a type of scan that uses magnetic fields and radio waves to create detailed images of the body — could be considered. This scan would look at the brain or the whole spine to rule out any conditions related to the upper motor neurons, which are nerve cells controlling the activities of muscles.
Treatment Options for Ankle Equinus
Healing an equinus condition in the ankle – where you have limited upwards bending or “dorsiflexion” of your foot – calls for a well-rounded strategy specifically matched with the root cause and intensity of the condition. There are non-surgical methods and surgical procedures available; both aim to restore normal movement in your ankle and relieve any discomfort you’re experiencing.
Non-surgical Treatment
Non-surgical treatments, also known as conservative management, are methods that don’t involve surgery. This type of treatment continues until you can walk with a heel-toe walking style, maintain good balance, and achieve sufficient bending at your ankle. Main aspects of non-surgical therapy includes:
- Physical therapy that focuses on stretching, strengthening, walking training, and exercising at home.
- Using casts and ankle-foot braces (primarily in children with equinus). The aim of the cast is to achieve at least 5° of ankle dorsiflexion. After achieving this, the cast can come off and you can begin a physical therapy and home stretching program.
For those who naturally walk on their tiptoes and have this condition, it’s important to get started with physical therapy after the cast comes off to help regain any muscle strength that may have been lost during the casting process.
Botulinum toxin A injections are another treatment option for patients with increased tightness and contraction in their ankle, especially for people with cerebral palsy. These injections function by reducing the overpulling of muscles in your lower leg.
Surgical Treatment
Surgery should typically be considered only when all other non-surgical treatment options have been tried, and the equinus condition continues. This often includes a procedure to release tension in one or more tissues, like the Achilles tendon or the group of muscles at the back of the leg.
The regions that could be lengthened during surgery are categorized into three zones, defined by Firth and his colleagues. Here’s a brief overview on what each zone involves:
- Zone 1: Begins from the upper area of the thigh where the major calf muscle starts (gastrocnemius) to the last part of the inner calf muscle. Lengthening in this area mainly targets the lengthening of the muscles within, as identified by Baumman and Koch.
- Zone 2: This includes the region from the end of the central calf muscle to the last part of the lower calf muscle, soleus. Lengthening at this level targets both the calf muscle and soleus.
- Zone 3: Begins from the lower region of the soleus muscle to the heel bone where the Achilles tendon connects. Lengthening the Achilles tendon is performed when your ankle condition doesn’t improve and the Achilles tendon is identified as the primary issue. This can be done with multiple small cuts to the tendon, either percutaneously (under the skin) or via open surgery.
Besides the commonly performed surgeries, there is another option for more complex deformities. This involves the use of a multiplanar external fixator, an external frame that you wear to correct the deformity gradually over weeks or months with the help of a computer software.
What else can Ankle Equinus be?
When trying to diagnose ankle equinus, doctors must rule out other conditions that could be causing similar symptoms. These symptoms might include limited movement in the ankle (known as dorsiflexion) and walking in an unusual or altered way.
The conditions that a doctor might consider when diagnosing ankle equinus include:
- Posterior ankle impingement syndrome: This is a condition where the back part of your ankle is pinched, which can limit dorsiflexion.
- Tightness of the gastrocnemius-soleus muscle: This muscle is in your calf, and if it’s too tight, it can restrict your ankle’s movement.
- Talar dome lesions or congenital foot deformities: These are abnormalities either in the ankle bone or in the foot that you’re born with, which may mimic or contribute to the symptoms of ankle equinus.
If the patient has a history of trauma (like an accident or injury), the doctor should check the bones of the ankle and back part of the foot to rule out any structural causes of the equinus contracture. Additionally, deficiencies in the motion of the hip or knee, or any limb length difference, should be checked to make sure they’re not contributing to the ankle equinus deformity. The presence of calcaneus deformity, which involves the weakening of the muscles in the back of the leg, causing issues with the ability to flex the ankle, should also be ruled out.
What to expect with Ankle Equinus
The outcome for a condition known as ankle equinus, where the foot points downwards limiting ankle motion, can vary, depending on what is causing it. For flexible ankle equinus, which is when the ankle can move back to the normal position on its own or with manual help, treatment often just includes physical therapy and stretching exercises that you can do at home.
However, in more severe cases that do not respond to these standard treatments, surgery might be necessary. A recurring issue though, is that the condition can return after surgery. The chance of the foot reverting back to the equinus position after a specific surgery, called a gastrocnemius recession, varies between 10% to 35%. In fact, the chance of reoccurrence is even higher amongst patients with neuromuscular disorders (conditions which impair your nerves and muscles). For example, in patients who had a different surgery called zone 1 lengthening, or Baumann procedure, 24% of those with a neuromuscular disorder saw their condition return, compared to just 10% of those without a neuromuscular disorder.
Possible Complications When Diagnosed with Ankle Equinus
Ankle equinus complications can be broken down into two categories, based on whether the treatment was conservative or operative.
Issues related to non-surgical treatments:
- Serial casting: There’s a risk of developing pressure sores or ulcers.
- Botulinum toxin A: This method has a low complication rate, similar to the rate for serial casting.
Problems that may occur after surgery to treat ankle equinus include:
- Achilles tendon lengthening: This can result in the loss of strength in flexing the foot downward.
- Gastrocnemius-soleus lengthening: There’s a risk of injuries to the lesser saphenous vein and sural nerve, in addition to losing the ability to flex the foot downwards.
Bear in mind that a significant complication with any lengthening procedure for ankle equinus is developing a heel-focused walk and weakness in the two important calf muscles. Although a second lengthening procedure can help with some problems, restoring strength to a weakened ankle foot downward flexing complex is difficult. Research also shows that specific lengthening procedures, like the Strayer procedure or Achilles tendon lengthening, may increase foot upward flexion post surgery but these are also known to increase the likelihood of weakening the calf muscles compared to other procedures, like the Baumann procedure.
Preventing Ankle Equinus
It’s crucial to understand and prevent worsening of ankle tightness, also known as ankle equinus. Knowing about the importance of regular stretches, especially for your calf muscles, can help keep or enhance the upward movement of your foot at the ankle joint. This can lower the chances of your ankle getting too tight.
Patients should also know about what could potentially cause ankle tightness, such as wearing shoes that don’t fit well, staying in one position for too long, and certain underlying health issues. Conditions such as diabetes, arthritis, severe obesity, cerebral palsy, autism, or a history of injuring your ankle can make it more likely that simple treatments won’t work. In these cases, you might need to be referred to a specialist.
It’s really important to take action early if you start to see symptoms to prevent more serious problems and improve your healing journey. Knowing how to choose the right shoes, modify your activities, and recognizing the importance of regular check-ups with health experts can empower you to manage your condition better. If basic treatments aren’t helping, teaming up with a specialist is really important to create a treatment plan that works best for you.
