How To Diagnose Lateral Ankle Injuries

Author(s): 
By Remy Ardizzone, DPM, and Ronald L. Valmassy, DPM

   The anterior drawer test consists of manipulating the affected ankle while taking a lateral X-ray view. To perform this test, it is important for the patient to lie partially on the affected side in such a manner as to obtain as true a lateral projection of the ankle as possible. The fibula should be slightly posterior to the line of the X-ray beam, mimicking its anatomic position. Placing the ankle in 10 degrees of plantarflexion improves the sensitivity of the test.14 One should perform an anterior displacement test on the talus by cupping the calcaneus and pulling forward and slightly downward with one hand while stabilizing the tibia with the other hand. There are various methods of measuring this test but typically the test is considered positive when there is a 10 mm excursion of the talus from under the tibia or 3 mm more than the contralateral side.15 Recent studies suggest that measuring the posterior excursion of the tibia from the posterior aspect of the talus may produce more reliable and reproducible measurements.16

   These tests also provide insight into which ligaments may be injured. An anterior drawer test indicates injury to the anterior talofibular ligament but does not necessarily exclude injury to the calcaneofibular ligament. The talar tilt test isolates injury to the calcaneofibular ligament.9

   While magnetic resonance imaging (MRI) may offer valuable information for an elite or professional athlete in the setting of an acute ankle sprain, it has little to offer when it comes to establishing a diagnosis of chronic instability. This requires dynamic testing such as the anterior drawer and talar tilt stress X-rays.17,18

Recognizing Cases Of Functional Instability

   Additionally, a subset of patients may have negative stress exams but still demonstrate frequent minor inversion industries and a sense of instability to the ankle. This condition describes functional instability as opposed to mechanical instability.5,8,19,20 Under these circumstances, the ligaments may only have healed in a somewhat slightly loosened position but the patient has failed to re-establish the proprioceptive connection to the brain.21 Proprioceptive fibers are embedded within the lateral collateral ankle ligaments and sustain injury along with the ligament itself.8,21,22

   One may assess proprioception in these patients by using a modified Rhomberg test. The patient stands on the normal ankle with his or her eyes open and then closed. Repeat this procedure on the symptomatic limb. Alternatively, the patient may rise onto the ball of the affected foot and perform five single leg hops.5-8 One of the key components of physical therapy is to reestablish these proprioceptive connections so the patient senses uneven surfaces and can recruit other muscles to stabilize the ankle and avoid inversion injury.23,24

   Other contributors to functional instability include impaired joint position sense, delayed peroneal muscle reaction time, altered common peroneal nerve function and muscle weakness.5,8

Pearls For Diagnosing Peroneal Tendon Injuries

   Injury to the peroneal tendons can manifest in several ways, including peroneal tendon tears, tenosynovitis and subluxation. During an inversion injury, the peroneus brevis and peroneus longus tendons fire in an attempt to evert the foot forcibly, thereby stabilizing the ankle to prevent it from inverting.25 This can result in a subtle, longitudinal tear to one of the tendons. The peroneus brevis tendon is commonly injured given its close proximity to the posterolateral tip of the fibula.26

   Additional contributing factors may attenuate the superior peroneal retinaculum. These factors include an anomalous tendon or low-lying peroneal muscle belly.27 This condition constrains the peroneal tendon within the fibular groove, leading to mechanical attrition of the peroneus brevis tendon against the sharp posterior ridge of the fibula.8,26,28,29

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