ANKLE INSTABILITY
Summary
Ankle instability is a condition whereby the restraining lateral [outside] ligaments of the ankle become stretched. This can lead to a sense of instability in the ankle and predispose the patient to frequent ankle sprains. Often patients with ankle instability can be treated without surgery by strengthening the muscles that control the ankle joint; avoiding high risk activities; and using a supportive brace or shoe to decrease the risk of recurrent ankle sprains. In some patients non-operative treatment is not successful and surgery is required to either tighten up the ligaments supporting the outside of the ankle or to reconstruct these ligaments using a tendon graft.
Clinical Presentation
Patients with ankle instability describe either a sense of ankle instability or a history of multiple ankle sprains - or often both of these. They often report a sense of their ankle rolling inwards more easily. They may also give a history of multiple ankle sprains. Not everyone is equally predisposed to sprain their ankle. Risk factors for ankle sprains include:
- A history of previous significant ankle sprains
- Hindfoot alignment where their heel position slopes inward towards the midline
- Generalized ligamentous laxity (loose ligaments)
- Participation in high-risk activities (ex. basketball and volleyball. Etc.)
Pain is commonly present in patients with ankle instability. However, the defining symptom of ankle instability is instability. Any associated chronic pain demands the treating physician identify the source of this pain. Associated injuries that cause pain are common with ankle instability. Sources of pain can originate from inside the ankle joint [intraarticular] or outside of the ankle joint [extraarticular]. Common sources of pain originating from inside the ankle joint include talar osteochondral injuries / lesions, impinging bone spurs, and ankle arthritis. Common sources of pain originating outside of the ankle joint include peroneal tendonitis, and irritation to the restraining lateral ligaments of the ankle joint.
For many patients pure ankle instability (i.e. a floppy loose ankle) needs to be differentiated from "functional ankle Instability." Functional ankle instability is essentially the sensation that an individuals ankle is unstable when in fact the ankle joint itself is still stable. What often happens with functional ankle instability is that when patients place their ankle in a certain position or load it in a certain way they will experience a pain (often sharp) that gives them a sensation that their ankle is loose. This can be caused by a problem inside the ankle joint such as a talar osteochondral lesion, ankle impingement, or ankle arthritis. It is important to identify whether a patient has true ankle instability (a loose floppy ankle) or functional ankle instability because the treatment is often different. Treatment of functional ankle instability is focused more on identifying and eradicating (or controlling) the source of pain.
Relevant Ankle Anatomy
Patients with true ankle instability have stretching out or even complete incompetence of some or all of the ligaments on the outside of the ankle joint. The two main ligaments in questions are the anterior talofibular ligament and the calcaeneofibular ligament. Incompetence of these ligaments can lead to looseness (inceased opening) of the ankle joint and/or the subtalar joint.
Physical Examination
On physical examination, the patient is likely to demonstrate increased inversion laxity. There may also be a positive anterior drawer test. A lateral stress test of the ankle may also be positive. These tests are done in comparison to the opposite ankle. It is not uncommon for patients to have the back part of the foot curving inwards (hindfoot varus) whereby the alignment of the heel slopes towards the midline of the body. If the patient does complain of chronic pain, this should be localized by palpation. This can help narrow the diagnosis based on the anatomical structures in this area.
Imaging Studies
Weight-bearing ankle x-rays should be performed to assess the ankle joint itself. The ankle joint mortise should be symmetrical.
Stress x-rays are often taken in patients with suspected ankle instability. By stressing the heel towards the midline while x-ray or fluoroscopic image is taken, a sense of how much the outside part of the ankle joint opens up. This should be compared to the opposite ankle. This will also help differentiate whether instability is originating from the ankle joint or the subtalar joint, or both.
In patients with chronic associated pain, an MRI may be indicated. An MRI will allow for assessment of potential intraarticular sources of pain such as a talar osteochondral injury or extra-articular sources of pain such as a tendonitis or scarring of the restraining ligaments. It should be noted that scarring of the anterior talofibular ligament is a common almost universal finding of most MRIs of the hindfoot regardless of whether patients have ankle instability or not.
Treatment
A history of multiple ankle sprains is one of the most common presentations of ankle instability. If the patient has recently had an ankle sprain that should be treated as any normal ankle sprain would be.
Non-Operative Treatment
For chronic ankle instability a combination of the following treatments is often successful at relieving symptoms and minimizing the risk of recurrent ankle sprains:
Therapy to strengthen the muscles surrounding the ankle joint.
These include exercises to strengthen the muscles that evert and invert the ankle, particularly the everting muscles that allow the ankle to resist inversion including the peroneus longus and peroneus brevis
Aggressive therapy to improve proprioception should also be performed. Exercises such as standing on one foot with the eyes closed and later on a soft surface with the eyes closed can be very helpful in improving proprioception.
Evaluation and treatment by a physical therapist.
The patient may benefit from strengthening and proprioception training under the guidance of a trained physical therapist.
Prophylactic splinting of the ankle.
Prophylactic ankle splinting with the use of an ankle stirrup, ankle lacer, or ankle taping can be very helpful in patients who are participating in high-risk activities.
With appropriate rehabilitation including strengthening and proprioception training as well as splinting or bracing as required, most patients with ankle instability can be treated nonoperatively.
Operative Treatment
Some patients will fail non-operative management and require or benefit from operative intervention. Typically, operative treatment is reserved for patients that suffer multiple ankle sprains or instability episodes that are not adequately controlled with non-operative management. In addition, patients with significant intra-articular pathology such as a talar OCL that are noted on clinical or intraoperative examination to have gross ankle instability will benefit from stabilization of the attenuated lateral ligamentous structures.
Anatomical repair of the outside (lateral) ankle ligaments (Broström procedure) including the anterior talofibular ligament and the calcaneofibular ligament is one common means of surgically stabilizing the ankle operatively. This procedure involves cutting the stretched out ligaments (anterior talofibular ligament and calcaneofibular ligament) on the outside of the ankle and repairing them in a tightened position.
Another similar operative treatment is a tendon reconstruction of the lateral ankle ligaments operative treatment. This procedure involves reinforcing the stretched out ligaments by weaving a tendon graft through bones in the outside of the ankle to provide increased support to this area.
A lateralizing calcaneal osteotomy may be required to realign the hindfoot in patients that fail an initial attempt at reconstructing the unstable ankle or patients with marked varus alignment. This is typically done using a Lateralizing calcaneal osteotomy. This procedure involves cutting the heel bone and shifting it to the outside. This bone cut is then stabilized with a screw.
Edited October 25th, 2009