Ankle instability is caused by injury to the lateral (outside) ankle ligaments. This usually causes strain or stretch, and in more severe forms causes sprain or tear in the ligaments. This can lead to a sense of instability (giving out) in the ankle and predispose the patient to get frequent ankle sprains even with minor trauma or twist.
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.
Some interesting statistics about Ankle Sprains:
- 1/10,000 persons/day
- 23,000 ankle sprains in the U.S. each day
- 40-45% of sports injuries are ankle injuries
- 85% of ankle injuries are sprains
- 85% of sprains are due to inversion with injury to the lateral ligaments
Inversion sprains (where the foot turns inwards) are the most common form of ankle sprain.
It damages the lateral ligaments of the ankle joint.
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 (ATFL) and the calcaneofibular ligament (CFL). Incompetence of these ligaments can lead to laxity (increased opening) of the ankle joint and/or the subtalar joint.
Signs & Symptoms
Patients with ankle instability relate either a history of multiple ankle sprains or a sense of instability – often both of these. They report a sense of their ankle rolling inwards more easily. They may also give a history of multiple prior ankle sprains. Things that make people at higher risk for suffering an ankle sprain include:
- A history of previous significant ankle sprains
- Hindfoot varus alignment where the heel position slopes inward towards the midline
- Generalized ligamentous laxity (loose ligaments)
- Participation in high-risk activities (eg. basketball, volleyball, etc.)
The defining symptom of ankle instability is the instability itself. However, pain is commonly present. Pain can originate from sources inside the ankle joint (intra-articular) or outside of the ankle joint (extra-articular). 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.
Pure ankle instability (i.e. a floppy loose ankle) needs to be differentiated from “functional ankle instability.” Functional ankle instability is defined as the sensation that an individual ankle is unstable when in fact the ankle joint itself is still stable. Commonly with functional ankle instability, 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 true ankle instability is focused on reconstructing the ligaments on the lateral side of the ankle, whereas treatment of functional ankle instability is focused more on identifying and treating (or managing) the source of pain.
Physical examination starts with gait and hindfoot assessment. 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. 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. 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.
X-rays are the starting point for evaluation of ankle instability. 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 also 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 is gained 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 pain, an MRI may be indicated. MRI is a sensitive test that usually identifies intra-articular abnormality, such as a talar osteochondral injury, or extra-articular sources of pain, such as tendonitis or scarring of the restraining ligaments.
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, it should be treated as any normal ankle sprain would be.
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.
- Therapy to improve ankle proprioception, or brain ankle coordination – 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 non-surgically.
Anatomical repair of the outside (lateral) ankle ligaments is one common means of surgically stabilizing the ankle. This procedure, called the Brostrom-Gould Procedure, involves cutting the stretched out ligaments (anterior talofibular ligament or ATFL and calcaneofibular ligament or CFL) on the outside of the ankle and repairing them in a tightened position.
Another surgical treatment is a tendon reconstruction of the lateral ankle ligaments. This more complex procedure involves reinforcing the stretched out ligaments by weaving a tendon graft through bones in the outside of the ankle to provide additional support to this area.
Post-surgery, patients typically need a 6-week period where the ankle is casted to allow for soft tissue healing. The cast is removed thereafter and the patient is allowed to walk on that leg and has to start a course of physiotherapy. Most patients can return to sports involving running and cutting at about 3 to 6 months after the surgery.
Recent Advances in Surgical Technique
The Bostrum procedure is now combined with the addition of an internal brace which helps to protect the repaired ligament during the initial healing phase. This allows the patient to start walking with a walker CAM boot from day 1 post-surgery followed by normal shoes by day 15 post-surgery. There is no need to use a full cast or crutches.