What is Lateral Ankle Instability?
Lateral ankle instability is a complicated issue that can sometimes be hard to assess and treat for regular doctors. This is partly because the ankle is made up of three joints: the talocrural, subtalar, and tibiofibular syndesmosis. All these joints work together to enable the wide range of movements we can make with our ankles. The stability of the ankle joint is ensured by the joint surfaces, the ligaments (tissue that connects bone to bone), and the muscles, which help dynamically stabilize the joints.
The outside or ‘lateral’ part of the ankle consists of the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligaments (PTFL). Each of these ligaments has a distinct role in maintaining ankle stability.
The ATFL starts from the front-side of the outer ankle bone and attaches to the lateral side of another ankle bone called the talus. The main job of the ATFL is to resist the foot from rolling inward excessively when it’s pointed downwards and to limit the forward and outward movement of the talus in the ankle joint.
The CFL starts from the front edge of the fibula bone, located near the tip and attaches to the heel bone (calcaneus). The CFL prevents the foot from rolling inward excessively when it’s in a neutral or extended position. It also helps limit the inward rolling of the subtalar joint, which restricts the tilting of the talus within the ankle joint. The CFR also extends beyond the ankle joint.
The PTFL, the strongest of the lateral ligaments, starts from the back edge of the fibula and attaches to a small outgrowth from the talus and runs at a right angle to the fibula. This ligament mainly assists in the stability of the ankle. It’s worth noting that out of the three ligaments (ATFL, CFL, and PTFL), only the calcaneofibular ligament (CFR) is located outside the ankle joint.
What Causes Lateral Ankle Instability?
Your ankle may feel unstable for two main reasons, either because of “functional instability” or “mechanical instability”. Mechanical instability typically happens because of a sudden injury or prolonged strain that causes wear and tear in the structures of your ankle ligaments. These are the tough tissues that connect bones to other bones.
The most common way that an ankle ligament gets injured is when force is applied to an ankle that’s rotated inward while the foot is pointing downward. This often happens as your body’s weight shifts over your foot. Of all the ankle ligaments, the ATFL (anterior talofibular ligament) tends to get injured the most, followed by the CFL (calcaneofibular ligament), and then the PTFL (posterior talofibular ligament).
If a ligament heals in a stretched out shape, it can cause deformation, which can limit its ability to provide support. On the other hand, functional instability stems from feeling like your ankle is unstable or experiencing repeated ankle sprains due to issues with body’s awareness of its movement and position, known as proprioception.
Lateral ankle instability can also happen due to a genetic tendency toward looser ligaments. This can be linked to conditions like Ehlers-Danlos syndrome, Marfan’s syndrome, and Turner’s syndrome.
Risk Factors and Frequency for Lateral Ankle Instability
Ankle sprains are the leading cause of sports-related injuries, accounting for 40% of all athletic injuries. More than half of basketball injuries and nearly a third of soccer injuries are due to this. Ankle sprains also contribute to over 10% of US emergency room visits, mounting up to about 30,000 cases a day. This type of injury mostly impacts the lateral part of the ankle and is just as likely in males as in females. However, there are reports that women are 25% more likely to have grade I sprains and are more prone to future sprains once they’ve had one.
- Ankle sprains are the main cause of athletic injuries, making up 40% of all sport-related issues.
- More than half of basketball and almost 30% of soccer injuries are ankle sprains.
- Ankle sprains account for more than 10% of US emergency room visits, equating to about 30,000 a day.
- Males and females are equally likely to have these injuries, but females may be more prone to grade I sprains and future sprains.
- 90% of all ankle sprains involve ATFL, a ligament in the ankle, 50-75% involve the CFL, and only 10% involve the PTFL.
- 55-72% of patients who sprain their lateral ankle continue to have symptoms afterwards.
- In the US, the incidence rate of ankle sprains in the general population is 2.15 per 1,000 person per year. In the military, this number can be up to 27 times higher.
Signs and Symptoms of Lateral Ankle Instability
If you frequently experience ankle instability or pain, it’s important to share your history and symptoms with a healthcare provider. Key details can help point towards the cause of the problem, such as recurrent or recent ankle sprains, or feelings of looseness or “giving way” on uneven ground. Some people may be more conscious of specific activities that put them at risk of further injury. Though pain may not be the primary concern, it’s still valuable information to communicate with your medical professional.
During a physical examination of the foot and ankle, the healthcare provider will look for certain characteristics that might explain the instability. They will assess:
- Alignment of the foot and ankle – certain shapes like high arches (cavus) or inward-leaning ankles (varus) can increase the chances of recurrent instability
- Hypermobility – very flexible joints might be more prone to injury
- Range of motion and strength – these should be compared to the opposite foot and ankle
In order to evaluate the condition of the ankle ligaments, the examiner will typically perform two specific tests: the talar tilt and anterior drawer test. If the foot shifts more than 8mm during the anterior drawer test, or if the talar tilt is greater than 10 degrees (or more than 5 degrees compared to the other side), it could indicate a problem with the ligaments in the ankle.
Testing for Lateral Ankle Instability
If a doctor suspects that a patient has lateral instability, they will carry out a patient history check and physical examination, and take x-ray images of the patient’s ankle. X-rays can help the doctor see whether the fibrous connection between the two bones of the lower leg, called the syndesmosis, has widened, and to identify any foot or ankle shape irregularities that might make the patient more likely to have instability.
Some additional specialized x-rays are also done. These include the anterior drawer test and the talar tilt test, which specifically check on the stability of the ankle. Patients who have mechanical instability (a physical problem with the ankle) will have visible signs on these tests; however, those with functional instability (where the ankle is unstable only when being used) might have no visible signs.
An MRI scan can provide a more detailed look at the outside of the ankle, and can also identify other possible problems such as injuries to the talar dome (the top of the ankle joint), issues with the peroneal tendons (the tendons that run along the outside of the ankle), and assist the doctor in planning any needed surgery.
The doctors will then categorize the injury to the outside of the ankle. Over the years, doctors have developed many ways to do this. The grading is as follows:
Anatomic (the actual injury to the ligaments):
– Grade I: The ligaments of the outside of the ankle have been stretched
– Grade II: One or several of the ligaments have been partially torn
– Grade III: The ligaments have been entirely torn.
Functional (how the injury affects use of the ankle):
– Grade I: The patient can fully bear weight and walk.
– Grade II: The patient walks with a noticeable limp.
– Grade III: The patient is unable to walk.
These stages include, the ATFL (Anterior talofibular ligament which is one of the main ligaments in the ankle) involvement:
– Stage I: Minor tears in the ATFL.
– Stage II: Major ATFL injury, with some injury to the CFL (a ligament that is also part of the outside of the ankle)
– Stage III: Injuries to both the ATFL and CFL, with both ligaments fully torn and loose upon examination.
Treatment Options for Lateral Ankle Instability
If your ankle is unstable after an injury, there are a number of ways you might be treated. Usually, you’ll start with rest, ice, raising the ankle, compression (like a bandage), moving it gently as much as you can, and gradually putting your weight back on it as it becomes less painful. You’re also likely to have physical therapy to help improve strength and mobility.
However, despite following these steps, between 10 to 40% of people experiencing an acute ankle sprain may develop long-term ankle instability. There’s plenty of research showing the benefits of both this non-surgical treatment and surgical treatment, which is used if your ankle doesn’t get better with the non-surgical approach.
More than 70 different surgical techniques exist to help correct ankle instability, broadly falling into three categories: anatomic, non-anatomic, and anatomic augmented tenodesis reconstruction.
Anatomic reconstruction, also known as the Brostrom procedure, directly repairs the Anterior Talofibular Ligament (ATFL), which is often damaged in ankle sprains. This procedure can also be enhanced by using nearby tissue (the extensor retinaculum) to improve the results.
Non-anatomic reconstructions do not repair the original ligament structure of the ankle. Instead, they use another tendon in your foot (peroneus brevis) to help stabilize the ankle.
Anatomic augmented tenodesis reconstructions combine the Brostrom procedure with additional natural tissue (either from your own body -autograft or from a donor – allograft), which can be attached using suture anchors or interference screws.
What else can Lateral Ankle Instability be?
When a doctor tries to figure out what’s causing instability in the outer part of your ankle, they’ll consider a variety of possible conditions. These can all lead to pain and weakness in this area:
- Inherited disorders that cause loose ligaments (like Ehlers-Danlos syndrome, Marfan’s syndrome, and Turner’s syndrome)
- Recent or past injuries to the ankle causing instability
- A broken bone
- Sinus tarsi syndrome, a condition causing pain on the outside of the foot and ankle
- Osteochondral defects – damage to the cartilage and underlying bone
- Peroneal tendinopathy, an injury to the tendons on the outer part of the ankle
- Instability in a joint located below the ankle called the subtalar joint
Your doctor would consider all these possibilities and would perform tests as necessary to land on the right diagnosis.
What to expect with Lateral Ankle Instability
Studies reveal that surgeries intended to restore the original anatomy of a damaged region tend to yield the best results. On average, 85-95% of patients experience good to excellent outcomes after the operation. However, patients who have poor tissue quality, persistent instability, or a specific type of foot shape with loose ligaments (known as cavovarus foot type) don’t recover as well after surgery.
Surgery intended for other purposes but not exactly restoring the original anatomy also showed positive results, with about 88% of patients reporting good to excellent outcomes. In addition, another study that looked at high-demand athletes suffering from chronic instability in the outer part of the ankle reported a 94% return to their previous sports following surgery.
Possible Complications When Diagnosed with Lateral Ankle Instability
Surgery can have several complications like persistent pain, infections, the procedure not being effective, injury to the nerves (3.8-9.7%), problems with wound healing (4%), stiffness, pressure due to tightening, removal of a limb, and even death.
Likewise, not undergoing surgery for chronic lateral ankle instability might lead to your ankle and the joint beneath your ankle losing balance. This could cause an early start to the wear and tear of your joint.
Possible Surgery Complications:
- Persistent pain
- Infections
- Ineffective procedure
- Nerve injuries (3.8-9.7%)
- Wound healing problems (4%)
- Stiffness
- Pressure due to excessive tightening
- Amputation
- Death
Possible Consequence of not Treating chronic Lateral Ankle Instability:
- Ankle and subtalar joint imbalances
- Early onset of joint disease (wear and tear of the joint)
Recovery from Lateral Ankle Instability
The goal of physical rehabilitation is to help you get back to your regular activity levels. This includes a set of different exercises that aim to increase the range of movement and build strength. As you progress in your recovery, additional exercises aimed at training the body’s sense of joint and body movement (proprioception) should be included. Finally, sports-specific activities should also be part of the rehab to fully prepare an athlete to get back to competing.
After surgery, your operated limb will be put in a cushioned splint, with your foot in a natural or slightly turned outward position. You’ll need to avoid putting weight on that limb until your surgeon advises otherwise. The stitches will be kept in place for about 2 to 3 weeks after the procedure. Once this time has passed, your surgeon may have you start gentle exercises to improve blood circulation in your veins. Then, you’ll be put into a short leg walking cast or boot, and will gradually be allowed to put more weight on the limb over the following 2 to 4 weeks. Following that, you’ll shift to an ankle support device and start a formal physical therapy program.
Keep in mind, the recovery and rehab process may differ for each person. It will be tailored by your surgeon taking into account the type of surgery you had and any additional procedures performed alongside the ankle stabilization.
Preventing Lateral Ankle Instability
If you get injured, the best course of action is usually to start with simple, non-invasive treatments. When the injury isn’t too severe, all you might need is rest, putting ice on the injured area, using a bandage to compress the area, and keeping it raised. This simple approach is often the best way to heal.
If the injury is more serious, you might need to start physical therapy. This is a type of treatment that uses exercises to help the body heal and improve function. However, in some cases, physical therapy might not be enough. If the injury doesn’t improve with physical therapy, surgery might become necessary.
The good news is, if you do need surgery, most people see great results. Typically, pain decreases and the body becomes more functional after surgery.
