Chronic Ankle Instability

What Is Chronic Ankle Instability?

Ankle instability is a result of weakness or laxness in the ligaments that surround the ankle joint (tibial-fibular-talar joint). It is a fairly common condition, especially in people who play high impact sports (basketball, football etc). Usually, ankle instability is a result of sprains injuring the ligaments.

Sprains can also damage other structures in the foot, and these secondary injuries can also contribute to symptoms of instability, pain and stiffness.

Ligaments are bands of tissue similar to tendons (fibrous tissue), and generally attach bone to bone. They act as stabilising structures around the bones that form the joint – similar to the way cables and guy ropes support bridges.

In the ankle there are two primary sets of ligaments that support the joint:

  • the triangular medial ligament (aka deltoid ligament), and
  • the lateral ligaments (the 3 main lateral ligaments include the anterior and posterior fibulotalar + the fibulo-navicular ligaments).

There is also a subtalar ligamentous complex that is involved in joint stability, but is difficult to describe.

The medial ligament sits on the inside surface of the ankle and is very strong. For this reason it is less likely to be the culprit in ankle instability. Conversely, the lateral ligaments sit on the outside of the ankle and are relatively weak. Consequently they are likely to be involved in instability, and also in sprains (see Ankle Sprain). Although the lateral ligaments sit on the outside of the foot, they prevent the foot from twisting inwards, so lateral chronic ankle instability involves a tendency of the foot to invert, rather the evert.

When ligaments are lax, muscles around the ankle can compensate for their weakness. When the lateral ankle ligaments are lax the ‘peroneus’ muscles can help support the joint . These muscles are long and thin and sit underneath the large calf muscles (gastrocnemius). They wrap around the outside of your ankle before attaching to the long bone that continues to become the fifth toe (base of the fifth metatarsal).

Diagram of the Foot looking from the side. It shows the ligaments that are commonly torn in ankle sprains

Symptoms

What are the symptoms?

  • A sense of weakness and instability in the joint – it feels as though the foot is always trying to collapse or ‘give out’.
  • Difficulty walking on uneven surfaces
  • Reduced proprioception – proprioception is the sense of the position of the joint in space. Someone with reduced proprioception in their ankle will sometimes find it difficult to maintain their balance  and walk on uneven surfaces.

Causes

Chronic ankle instability usually develops following an ankle sprain that has overstretched the ankle ligaments.

When you sprain your ankle, the ligaments are stretched or torn. Proper rehabilitation is important to strengthen the muscles around the ankle and “retrain” the tissues within the ankle that affect balance.

Repeated ankle sprains leads to further weakening (or stretching) of the ligaments, resulting in greater instability and the likelihood of developing additional problems in the ankle.

Risk Factors

  • Previous history of ankle sprains – in some sprains, the ligaments do not recover fully and chronic ankle instability follows
  • Playing high impact sports
  • Slight deformities in the talus bone can increase the relative strength of the ligaments to the risk of the bone being twisted out of place. Similarly, problems in the talarcrural joint can increase the risk of sprains and chronic ankle instability.
  • Hindfoot varus – people with this deformity tend to have a higher risk of ankle instability and difficulty maintaining posture

Investigations

Chronic ankle instability is assessed through physical examination by a doctor, physiotherapist or other health specialist. This may involve:

  • Looking carefully at the foot and ‘palpating’ (feeling carefully) the different joints
  • Assessing range of motion around the joints, both active (you move your own joint) and passive (the doctor moves your joint)
  • Strength of muscles around the ankle, especially the strength of the peroneus muscles (these are very important in compensating for lateral ankle instability)
  • Special stablity tests – the doctor or physio may pull gently on the joints in different directions to test how much the ligaments are able to resistThis video from youtube shows a physio testing the joint for ligament weakness across the front of the ankle. The normal left foot is shown first, then the weak right foot is shown. Notice the way the right foot seems to move too far forward in relation to the leg when the physio pulls it. 
  • Special proprioception tests

Complications

What are the Complications  of Ankle Instability?

  • High risk of sprains – chronic ankle instability is caused by sprains, but then goes on to cause more sprains – a vicious cycle.
  • Ankle instability causes the bones to sit in a relatively abnormal position, which increases the risk of osteoarthritis in the foot, knee, hip and spine, as well as increasing the risk of flatfoot deformity developing.
  • Approximately two-thirds of people with chronic ankle instability have bone, or ‘articular’ injuries, usually due to the initial sprains also damaging other structures. Because lateral ankle instability is more common, these secondary injuries are often found on the medial (inner) surface of the foot, where the sprain has caused the compression (‘impingement’) of soft tissues and bone.

Differential Diagnosis

  • Other causes of instability – tendon rupture, peroneal muscle dysfunction, fractures, ‘degenerative’ changes in the foot joints, ie osteoarthritis.

Further tests may include:

  • X-Rays – your doctor or physiotherapist will usually be able to assess your ankle instability without X-Rays, but imaging your ankle can sometimes be useful to see the degree of instability; ‘stress’ X-Rays can show how much the ankle is twisting out of place when put under strain. X-Rays can sometimes also be taken to look for arthritis or subtle fractures.
  • MRI – MRI is very good at showing the soft tissues around a joint but will only be taken if considered necessary. In chronic ankle instability MRI may be useful in showing how damaged the ligaments are, ie whether they are stretched, deformed or torn, as well as any swelling around the joint.

Complications

What are the Complications  of Ankle Instability?

  • High risk of sprains – chronic ankle instability is caused by sprains, but then goes on to cause more sprains – a vicious cycle.
  • Ankle instability causes the bones to sit in a relatively abnormal position, which increases the risk of osteoarthritis in the foot, knee, hip and spine, as well as increasing the risk of flatfoot deformity developing.
  • Approximately two-thirds of people with chronic ankle instability have bone, or ‘articular’ injuries, usually due to the initial sprains also damaging other structures. Because lateral ankle instability is more common, these secondary injuries are often found on the medial (inner) surface of the foot, where the sprain has caused the compression (‘impingement’) of soft tissues and bone.

Differential Diagnosis

  • Other causes of instability – tendon rupture, peroneal muscle dysfunction, fractures, ‘degenerative’ changes in the foot joints, ie osteoarthritis.

Treatment

There are lots of different forms of treatment available for chronic ankle instability.

Non-surgical treatment of Ankle Instability

The mainstay of treatment is however physiotherapy and exercises at home. This aims to increase support around the joint and prevent further strains by improving proprioception (sense of balance), and protect the shape and normal function of the foot (ie avoid the development of flatfoot deformity).

A physiotherapy regime for ankle instability concentrates on improving your:

  • Proprioception – this often involves wobble board exercises. The aim of proprioceptive exercises in this case is to increase your awareness of the position of your foot when it is under load (ie weight-bearing). The proprioceptive exercises also have the added bonus of building strength.
  • Strengthening – strengthening exercises are particularly important as compensation for lax ligaments. Physiotherapists will focus on training the lateral peroneus muscles, as well as working on the medial muscles to maintain the balance of forces acting across the ankle.

Bracing and Taping

Further treatment may include bracing and taping to provide extra support, and you may be referred on to see an orthoptist. In general, physiotherapy is very successful at treating instability both short and long-term.

Thinks to do at home if you’re waiting to see a physiotherapist:

  • Pain releiving medications. You can take over-the-counter painkillers if pain is a major issue
  • Ice. ice and elevating your foot can help to reduce swelling
  • Shoewear. Adequate footwear/boots that support the ankle may be helpful,
  • Uneven surfaces. Being aware of uneven surfaces that may lead to ankle sprains, and taking care to place your foot carefully

If you’ve googled ankle instability you will probably be aware that there are a number of strengthening exercises that can be done to increase support for the ankle. It is very important you do not do these yourself at home without first seeing a physiotherapist. If you have a normal ankle then these exercises can be done without danger, but if your ankle is already injured and you perform these exercises incorrectly you can do further damage.

Surgery

Surgery may be recommended for your ankle if your ankle is unstable despite physiotherapy and bracing.

Ankle Stabilisation ( ligament reconstruction )

In severe cases a lateral ligament reconstruction may be needed. There are a number of different operations available for lateral reconstruction. In general, surgery involves taking a section of ligament from somewhere else and attaching it to the bones to replace the lost support. Usually, outcomes including stability, range of motion, and painless weight-bearing for ankle reconstruction are quite good.

Arthroscopy – arthroscopy can be used in conjunction with other forms of treatment for chronic ankle instability, but can also be used alone. The purpose of arthroscopy in this situation is to assess the presence of complications (see above) associated with chronic ankle instability and address these if possible.

Post-operative rehabilitation for ligament reconstruction usually involves immobilising the ankle in a cast for around 2 weeks, then changing to a removable ankle brace so that physiotherapy can begin to improve the range of motion and flexibility around the joint. After a few more weeks, you can start to weight-bear and return to your normal activities, however it may be necessary to continue wearing a brace, especially when doing demanding activities, long-term.

Surgery may not be appropriate if:

  • Your surgeon thinks the benefits are not sufficient to outweigh the risk. For example, you may have a lot of pain with only a little instability. If this is the case, then reconstruction of the ligament will not fix the main problem (pain) and is therefore not worthwhile.
  • You have serious peripheral vascular disease – the reduced blood flow to the foot may impact on how well the ‘new’ ligament settles into position, as well as how well the foot itself heals. Furthermore, peripheral vascular disease significantly increases the risk of infection.
  • Peripheral neuropathy


Relatively common complications of ankle ligament reconstruction:

  • Recurrent instability & stiffness – this can occur in the immediate post-op period and is addressed with physio and other allied-health professionals. However, this can also long-term and more difficult to treat.
  • Wound problems – failure to heal, infection
  • Nerve damage – in particular, the superficial peroneal nerve and sural nerves. Sometimes neuromas can develop.

Probably the most important problem with surgery is that you may not feel your ankle has been improved. Your surgeon may look at the X-Rays and MRI and think that the ligament is now fixed, but your experience of your ankle may be that it is too stiff or too weak to return to your former activities. While this is fairly rare – ankle reconstruction is generally quite successful – it is a possibility and it’s important to remember that even when surgery and post-op treatment are perfect it is not possible to give you a brand-new uninjured ankle. It is also important to remember that the goal of surgery is to make the ankle stable, not to create an ankle that can perform all the high-demand activities associated with lots of sports etc. You should discuss with your surgeon your expectations of function after surgery so that both of you understand what is possible and what you need to be able to perform your daily activities and return to work.

Seeking Advice

Your Family Doctor (GP)

Your Family Doctor will be able to diagnose and help treat your problem. He or she will be able to

  • tell you about your problem
  • advise you of the best treatment methods
  • prescribe you medications
  • and if necessary, refer you to Specialists (Consultants) for further treatment

F.A.Q. | Frequently Asked Questions

More Information

Please note that the accuracy of any information provided by external sites is not guaranteed by Orthoanswer. Always discuss your condition with your doctor/health specialist.

  • About.com provides lots of information about ankle sprains, instability, treatment options etc. http://orthopedics.about.com/cs/sprainsstrains/a/anklesprain_4.htm 
  • Pueblo Ankle and Foot Care is an American site that provides brief, easy-to-understand information about many foot and ankle conditions: http://www.puebloankleandfoot.com/conditions/chronic-ankle-instability

References

F. Bonnel, et al., ‘Chronic Ankle Instability: Biomechanics and pathomechanics of ligaments injury and associated lesions’, Orthopaedics and Traumatology: Surgery & Research, Vol 96, Iss. 4, June 2010, pp 424-432.
K. W. Chan, ‘Acute and chronic lateral ankle instability in the athlete’. Bulletin of the NYU Hospital for Joint Diseases, 2011, Vol. 69, Iss. 1, pp 17-26.
PO McKeon PO, et al., ‘Balance training improves function and postural control in those with chronic ankle instability’, Medical Science Sports Exercise, 2008, Vol 40, Iss. 10, pp 1810-1819.