Ankle instability
Functional ankle instability / chronic ankle instability / frequent ankle sprains

Ankle instability involves pain and a feeling of instability in the ankle. The symptoms usually occur as a result of previous ankle sprains. Ankle instability increases the risk of frequently spraining the ankle.

foot lateral muscles tendons ligaments ankle

Ankle instability occurs in every age group. It is more commonly seen in athletes who play contact sports such as football or soccer.

Description of condition

The ankle joint is held together firmly by the ankle ligaments and muscles that move the ankle. Thanks to the combination of muscular functions and the rigidity provided by the ankle ligaments, the ankle feels "stable". Unfortunately, this may change when the ankle is damaged.

In an acute ankle sprain, the ankle usually tilts inward, causing damage to the lateral ankle ligaments. Tearing the ankle ligaments allows the ends of the ankle ligaments to move further apart. As a result, ankle ligament injuries cause an immediate loss of stability (strength) in the ankle. This is referred to as ankle instability.

We differentiate between short-term and long-term ankle instability. In most cases, ankle instability is short-term. The body recovers by itself, for instance after spraining your ankle. If the symptoms last longer than 12 weeks, there is a structural loss of stability and this is referred to as long-term ankle instability.

Ankle instability that lasts longer than the normal recovery process can be split into two categories. There is functional ankle instability and mechanical instability.

Functional ankle instability
When we speak of functional instability, the ankle ligaments have recovered, but the muscles are too weak or react inadequately. This means that the body is unable to actively provide enough strength to the ankle.

The ankle ligaments, muscles and the joint capsule contain sensors that track movements in the ankle. Because your body gets information about movements in the joint in this way, your muscles can react quickly if you are about to stumble. Following an ankle injury, these sensors may get damaged and not function well. Consequently, it becomes a lot harder for your muscles to react quickly and correctly if you are about to sprain your ankle.

Mechanical ankle instability
If there is mechanical ankle instability, the ankle ligaments are not strong enough or have not healed properly. This is also referred to as laxity (weakness) of the ankle ligaments. As a result, there is too much mobility in the ankle joint so the ankle remains unstable.

Ankle instability is often a combination of mechanical and functional instability. The ankle ligaments did not recover very well or have become overlong, giving mechanical instability. The sensors in the ankle ligaments cannot function properly as a result of this. If you do not train after an acute ankle sprain, functional instability develops.

Cause and history

Ankle instability is usually caused by a previous ankle sprain. Ankle instability may also be the result of a congenital abnormality of the ankle structures that should provide stability. This is however not common.

Long-term ankle instability develops in 20% to 40% of people with an ankle sprain. To prevent long-term ankle instability from developing, it is important that an ankle sprain is treated properly.

Signs & symptoms

Persistent pain or repeated sprains are the most common symptoms of ankle instability. The pain is usually on the outside of the ankle. In addition, there is often a feeling of instability when walking on uneven ground, and a fear of new sprains during (sports) activities.

Symptoms of ankle instability:

  • Feeling uncertain about the ankle when walking and/or playing sports.
  • Repeated spraining of the ankle.
  • Pain in the ankle area, usually on the outside of the foot.
  • Feeling of instability in the ankle when walking on uneven ground.
  • Fluid in the ankle after straining.

Symptoms of functional instability:

  • Disrupted coordination of the ankle.
  • Loss of ankle stability.
  • Loss of muscular strength in the ankle.
  • Movement anxiety (not really daring to place weight on the ankle).
  • Reduced flexibility (mobility) in the other joints of the ankle and foot.

Symptoms of mechanical instability:
Increased movement within the ankle as a result of ankle ligaments being too loose.


An initial diagnosis is made after the physiotherapist has asked the patient some questions. They will ask about previous ankle sprains and the feeling of instability at the time. This is followed by a physical examination to determine whether there is actual ankle instability.

For functional ankle instability, the degree of interdependent muscular function, coordination and muscle strength is assessed. Loss of coordination and stability can mainly be measured by tests on one leg. The affected ankle will have more difficulty stabilizing and will tire more easily during these tests.

Mechanical instability can mainly be determined if there is laxity of the ankle ligaments. In addition, the mobility of each joint in the foot and the ankle is examined.

X-rays or an MRI can help make the right diagnosis. These additional examinations are initiated if another injury is suspected or to assess the quality of the ankle ligaments.


The treatment of ankle instability depends on the results of the physical examination and the patient's level of activity.

Non-surgical (conservative) treatment consists of physiotherapy, using an ankle brace and/or medication. Medication is only used if inflammation is present that does not go away after rest.

Physiotherapy will always consist of exercise therapy aimed at coordination, balance, coordinated muscular function and muscle strength. If only limited movement is found in the foot or ankle, a physiotherapist can treat this by mobilizing the joints.

The aim of the treatment is to stimulate a good recovery and prevent future ankle sprains. Each ankle sprain results in a greater likelihood of premature wear and tear on the joint.

Ankle brace
An ankle brace can be used to prevent new sprains. It is used primarily during sports activities. The use of an ankle brace is functional and does not result in a loss of stability of muscle strength in the long run. The ankle brace may be used for both mechanical and functional ankle instability. But a brace is more likely to be advised if mechanical ankle instability is the cause.

In some cases of mechanical ankle instability, surgery will be considered. The orthopedic surgeon will decide in consultation with the patient whether surgery is desirable. The degree of instability, bad reactions to previous treatments and the level of activity of the patient play an important role in this.

In terms of the level of activity, the patient's occupation and/or level of sport are the most important factors. Patients who have a sedentary occupation will be advised to undergo surgery a lot less quickly than for instance members of the military. The same applies to top athletes who require more use of their ankle than people who play sports at a lower level.

In case of surgery, the (lateral) ankle ligaments are repaired. The rehabilitation period usually lasts between 5 and 9 months before resuming sports. Due to this long rehabilitation period, patients often opt to use a brace to prevent further sprains rather than undergo surgery.


Exercises are recommended to improve ankle stability. Follow the exercise program of ankle instability exercises here.

You can check your symptoms using the online physiotherapy check or make an appointment with a physiotherapy practice in your locality.

ankle talofibular calcaneofibular tibiofibular ligaments anatomy

Brukner, P. & Khan, K. (2016). Clinical sports medicine (Nederlandse bewerking). 4th edition. Michel van Troost. PreVision, Eindhoven.
Fraser, J.J., Feger, M.A. & Hertel, J. (2016). Clinical commentary on midfoot and Forefoot involvement in lateral ankle sprains And chronic ankle instability. Part 2: clinical considerations. The International Journal of Sports Physical Therapy. Volume 11, Number 7, December 2016.
Hiller, C.E., Kilbreath, S.L. & Refshauge, K.M. (2011). Chronic Ankle Instability. Evolution of the Model. Faculty of Health Sciences, University of Sydney, New South Wales, Australia.
Wees, Ph.J. van der, Lenssen, A.F., Feijts, Y.A.E.J., Bloo, H., Moorsel, S.R. van, Ouderland, R., Opraus, K.W.F., Rondhuis, G., Simons, A., Swinkels, R.A.H.M., Vaes, P., Verhagen, E., Hendriks, H.J.M., Bie, R.A. de (2006). KNGF-richtlijn. Enkelletsel. Jaargang 116. Nummer 5. Update klinimetrie 2017.

foot lateral muscles tendons ligaments ankle
ankle talofibular calcaneofibular tibiofibular ligaments anatomy

© Copyright 2024   |   All rights reserved   |   Privacy   |   Design: SWiF