Following a lateral ankle injury, a patient often presents with swelling, pain, decreased ROM, an acute joint dysfunction, and decreased proprioception in the foot and ankle. Depending on the severity of the injury, these symptoms usually begin to improve within a matter of weeks. However, occasionally symptoms persists despite doing all the proper things during your treatment sessions.
Most commonly, if a lateral ankle injury occurs the Anterior Talofibular Ligament (ATFL) will be stressed and injured. The mechanism of injury stressing the ligament typically includes adduction and traction of the talus on a plantarflexed and inverted foot. What many individuals fail to consider is the close interaction between the Intermediate Dorsal Cutaneous Nerve (a branch of the superficial peroneal nerve) and ATFL. The Intermediate Dorsal Cutaneous Nerve courses just superior to the ATFL and can also undergo a significant amount of stress during a lateral ankle inversion injury. The nerve is purely sensory and provides sensation to the dorsal aspect of the foot. When the nerve has been irritated, common clinical findings include pain, paresthesia, and a + Tinel's Sign.
To check for neural tension in the superficial peroneal nerve (you cannot solely tease out the Intermediate Dorsal Cutaneous Nerve), have the patient lie in supine. Bring the affected foot and ankle into plantar flexion and inversion. Next, perform a straight leg raise on the affected limb while maintaining the foot in PF and Inversion. If pain increases, this is positive neural tension. It is very important to perform the straight leg raise because if you only perform PF and Inversion, pain could be coming from either the ligamentous injury or neural tension. You must further tension the nerve proximally.
One should be quick to point out that neural tension may be present, but it is not always the cause of a person's symptoms. In order for the neural tension to be considered relevant adverse neutral tension it must fulfill 3 criteria:
1) Does the test reproduce their pain?
2) Is there a side to side difference?
3) Does the pain change by moving a distant component?
Assessing neural tension is one quality that differentiates the novice clinician from an expert. Next time you see a lateral ankle injury, consider the interaction between the Anterior Talofibular Ligament and the Superficial Peroneal Nerve.
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