Not All Ankle Sprains Are Equal

Ankle Sprain Mechanisms

Injuries to ankle ligaments typically fall into one of two buckets. Lateral ankle sprains are the result of an inversion with plantarflexion stress and syndesmotic, AKA high ankle sprains, are attributed to forceful dorsiflexion with eversion. Approximately 85% of ankle sprains injure the lateral ligaments. This is primarily due to the more distal projection of the lateral malleolus and the very strong deltoid ligament. Of the lateral ligaments, 60-70% of the injuries are to the anterior talofibular (ATF) ligament, 20% involve to ATF and calcaneofibular (CF), and 14% are avulsion injuries.

Ankle Sprain Symptom

Symptoms include edema, pain, ecchymosis, and possibility instability. The magnitude of the symptoms are used to classify the sprain as grade I, II, or III. The chart below summarizes the grades:

Ankle Functional Questionnaires

In addition to the clinical signs and symptoms, there are a variety of clinical questionnaires to help the clinician appreciate the functional limitations of a patient with an ankle injury. Here are a few:

Cumberland Ankle Instability Tool (CAIT) http://www.archives-pmr.org/article/S0003-9993(06)00519-3/pdf
Foot & Ankle Ability Measure (FAAM) https://www.sralab.org/sites/default/files/2017-06/Foot%20and%20Ankle%20Ability%20Measure.pdf
Foot & Ankle Disability Index (FADI) Score https://www5.aaos.org/uploadedFiles/foot_and_ankle_disab.pdf

Lateral Ankle Sprain Tests

To test the lateral ligaments, the anterior drawer and talar tilt are the primary tests. The anterior drawer test stresses for ATF to determine laxity. The ATF connects the tibia and the fibula so displacing the calcaneus anterior on the stabilized tibia-fibula will incriminate this ligament. To perform this test, the patient is in supine with the distal tibia/fibula stabilized and the posterior calcaneus/talus grasped to translate anterior on tibia/fibula, i.e. distal moved on proximal. A positive test is pain and/or excessive gapping. You should also note, the presence of a “dimple” anterior to the tip of the lateral malleous during the drawer test is a positive indication of an ATF ligament rupture. This “dimple” is the result of negative pressure created by anterior displacement of the talus drawing the skin inward.

A study by Kovaleski et al (2008) examined the influence of knee and ankle position on anterior ankle laxity. Stiffness was determined to be greatest at 0° of knee and ankle flexion. Laxity was maximal at 90° of knee flexion with 10° of plantarflexion. Therefore, if testing is performed in a position of maximal stiffness and laxity is determined to be present, it can be attributed to ankle capsuloligamentous structures.

A recent study that examined the use of the Mobil–Aider Arthrometer reported a 1.1 mm difference between the injured and uninjured ankles was consistent with a grade I ankle sprain and a difference of 2.2 mm was consistent with a grade II ankle sprain. This quantitative information is critical in driving the plan for interventions (Taweel, Gulick, Palombaro, 2022).

The talar tilt test has three alternatives to enable the clinician to implicate any one of three ligaments: ATF, CF, posterior talofibular (PTF). In order to do this, the clinician stabilizes the lower leg and grasps the calcaneus to apply a varus stress. The position of the ankle determines the primary ligament stressed: plantarflexion = ATF, neutral = CF, and dorsiflexion = PTF. Draw - Talar Tilt Stats 2 That is not to say the other ligaments are not stressed in the respective positions but it would not be the ligament of maximal stress. A positive test is pain and/or excessive gapping. The statistical values for these tests demonstrate the confidence by which they should be interpreted.

Syndesmotic Ankle Sprain Tests

The syndesmotic tests include the squeeze, external rotation, cotton, and fibular translation tests. A syndesmotic sprain is one in which the ankle mortise, the junction of the tibia and fibula, is separated. This occurs with forceful dorsiflexion as the wider base of the trapezoidal shaped talus forces the tibia and fibula apart. The syndesmotic squeeze test can be performed in supine or sitting. It begins at the proximal tibia/fibula and the clinician begins squeezing the tibia/fibula together proximally and progresses distally towards the ankle until pain is felt. The squeezing motion will gap the syndesmosis and the farther from the ankle that pain is elicited, the more severe the sprain. Care must be taking to squeeze the tibia/fibula and not anterior/posterior soft tissue. This is not meant to be a Homan sign for DVTs.

The external rotation test (AKA Kleiger test) is performed in supine with the knee flexed to 90°. The clinician uses one hand to support the lower leg. The other hand supports the talocrural joint in neutral and imparts an ER force to the ankle to displace the fibula laterally to open up the mortise. Reproduction of pain is a positive test.

The Cotton (Shunk) test utilizes a lateral translation against the fibula to separate the mortise. In supine or sitting, the clinician stabilizes the distal tibia and grasps the rearfoot with the other hand. Note the rearfoot is translated medial and lateral. This is not an inversion and eversion motion to produce gapping. A positive test is translation in either direction of more than 3-5 mm or the presence of a “clunk.” Assessment of millimeters of translation is challenging. The Mobil–Aider device can provide this data.

The fibular translation test places the client in contralateral sidelying for the clinician to apply an anterior-posterior force (sagittal plane) to the distal fibula. Increased translation as compared to the contralateral side would be a positive test.

Aside from the external rotation test, there is no sensitivity or specificity reported for the syndesmotic tests. However, a study conducted by Beumer et al (2003) looked at the different tests for the syndesmotic ankle instability, with the purpose of determining the best tests to identify laxity. With the systematic sectioning of precise ligaments, they looked at the squeeze, the fibular translation, the cotton, the external rotation, and the anterior drawer. The charts below summarize the data for anterior and posterior displacement of the syndesmosis. Data reveals the External Rotation Test produces the most anterior gapping while the Cotton, Fibular Translation, and Anterior Drawer tests produce similar magnitudes of posterior gapping.

In summary, a positive test of all ankle ligamentous tests is pain and/or increased translation of the joint. It is always helpful to make a contralateral comparison if the other ankle is healthy. For more cutting edge orthopedic information in iOrtho+ Premium Mobile App, please visit https://iortho.xyz/

For more information on the Mobil–Aider Arthrometer, please visit: https://mobil-aider.com/

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