Lateral Ankle Sprains CPG: Course, Diagnosis, and Exam

Today Austin takes us through the 2021 update of the lateral ankle sprain CPG, also called the "Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision - 2021" guideline.

Transcript

 Clinical course, Diagnosis/classification, Examination 

Hello and welcome back to the OCS field guide podcast. Today will be part 1 of our coverage of the Ankle Stability and movement Coordination Impairments: lateral Ankle ligament sprains 2021 revision, its about as long as the name, but we’ll do our best to condense this down to what you need to know. 

This CPG looks at acute lateral ankle sprain and chronic ankle instability. Lateral ankle sprains are among the most common injuries sustained, but only about 50% of individuals who sustain an ankle sprain actually seek medical attention. Even still, it is the most common foot/ankle injury for which individuals seek care. Of those only 7-11% those who do seek care are referred to a rehab specialist. Maybe this is part of why the recurrence rate is so high. Incidence of Chronic ankle instability in various younger athlete populations are as high as 20-29%. The highest rate of injury occurs between 14 and 37 years old. Ankle sprains occur much more frequently in indoor court sports than field sports with incidence rates of about 7 injuries per 1000 exposures in basketball and volleyball compared to 1 injury per 1000 exposures in field sports. That will be important to remember for injury prevention in our next podcast.

Recurrent ankle sprain and chronic ankle instability are also much more prevalent in female athletes, and are more prevalent in high school athletics than collegiate levels. At the collegiate level, about 12% of all reported ankle sprains were recurrent injuries, and were most often sustained in women’s basketball, outdoor track, and field hockey; and for men were most often sustained in basketball. However these numbers are likely all lower than reality, as they are from retrospective studies, and we know half of injuries are not reported. The only prospective study performed to date showed that the that 40% of individuals who sought care for a first-time lateral ankle sprain went on to develop chronic ankle instability. Now, that was a lot of numbers that you don’t need to remember. Just bear in mind that ankle sprains are very common, especially in females and adolescents, and especially in court sports. A very high percentage of individuals who have a new acute lateral ankle sprain will develop chronic ankle instability, which likely has implications for how much we should be treating these individuals. 

Pathoanatomic features:

Let’s talk about he pathoanatomic features of lateral ankle sprain. When talking about lateral ankle sprain we have classically just talked abut it in terms of how badly injured the anterior talofibular ligament and potentially calcaneofibular ligament are sprained. However the pathoanatomy of this injury is much more nuanced with a number of common concomitant injuries often present. The most common is bone bruising which can be noted on MRI. Ankle effusion is very common and can be associated with the severity of the associated injuries, however the amount of swelling is not associated with whether or not a fracture is present. Ankle impingement symptoms are also very common following lateral ankle sprain affecting 25% of individuals and potentially accounting for pain with gait either due to soft tissue injury, post-traumatic osteophyte formation, or altered kinematics due to lengthened ankle ligaments. Other common injuries associated with lateral ankle sprain include fibularis muscle or tendon injury, os trigonometry syndrome, osteochonral injury, syndesmotic or deltoid ligament injury, mid foot joint injury, and nerve pathologies. For a more in depth look at a lot of these injuries, check out our most recent study session on our Patreon page that David led on the ankle and foot, where he does an excellent job of distilling a ton of info on all the most common traumatic and atraumatic ankle/foot pathologies. Beyond these more anatomical features, the other features listed include sensorimotor and ROM deficits leading to altered movement patterns. That will be more fleshed out as we work through the other sections. Individuals that recover from a lateral ankle sprain with in a year with near normal function and return to activity are considered “copers,” while those that do not are considered to have chronic ankle instability. The pathoanatomy of chronic ankle instability does not have a lot to do with specific structure. Actually, development of CAI is not associated with how many ligaments are injured in a sprain. Though there does seem to be more CAI with more severe concomitant injuries such as those listed above. However the biggest influence appears to be persistent sensorimotor and ROM deficits at the foot, ankle, knee, and hip, with the following issues often present: abnormal timing of muscle activation, decreased force output/strength, impaired proprioception, decreased ankle DF ROM, and increased subtler and mid foot motion, as well as complicated sounding centrally mediated things like impaired spina-level sensorimotor control and reflex-inhibition and supra spinal corticomotor abnormalities. 

Risk Factors:

This CPG breaks down risk factors into acute and chronic LAS and intrinsic vs extrinsic and modifiable vs non-modifiable. I feel the short summary likely includes what you need to know. The most pertinent risk factors for acute lateral ankle sprain are: female sex, hip abductor and extensor weakness, poor performance on balance and hop tests, and participating in a court sport. You heard that right: just participating in a court sport vs field sport puts you at higher risk for acute lateral ankle sprain. So think, females with weak hips playing basketball and volleyball, and you have your highest risk group.

The following are the risk factors for developing chronic ankle instability: not using prophylactic bracing, not participating in an exercise-balance program and poor functional performance after a lateral ankle sprain, participating in sports in general, and higher BMI. It is interesting how the two differ, because not using bracing and higher BMI are not risk factors for acute lateral ankle sprain, but they are for the chronic side.

Let’s talk about the clinical course of an ankle sprain. The CPG splits this into acute and post-acute, and then chronic ankle instability. Acute is defined as the first two weeks following an injury where the post-acute period could last up to 12 months following an injury. The recovery following an ankle sprain is varied. Full return to participation is typically somewhere between 1 day to a little more than 3 weeks, but full recovery with no symptoms or limitations may take months or years and cannot be expected in all patients. However, evidence supports that a supervised impairment-driven exercise program can allow for a faster recovery and help prevent re-injury. From this the authors make a B-level recommendation that clinicians include the following in an initial evaluation, as these factors likely influence the clinical course and time to recovery following a lateral ankle sprain: patient age, BMI, pain coping strategies, report of instability, history of previous sprain, ability to bear weight, pain with weight bearing, ankle dorsiflexion ROM, medial joint-line tenderness, balance, and ability to jump and land (when safe). That being said, there is no algorithm or specific cutoffs for these values overall that give us more cut and dry prognosis, but overall worse or poorer scores or values in these areas are going to lead to longer time to recovery.

Now for chronic ankle instability. In general people are considered “copers” after LAS if their symptoms of pain and instability are gone in under a year. If they have pain or instability extending beyond one year, they are classified under chronic ankle instability. About 40% of first-time ankle sprains will go on to develop chronic ankle instability. Those that go on to develop Chronic ankle instability may have sensorimotor and ROM impairments at the trunk, hip , knee, ankle , and foot as well as impaired central mediated processes. So the CPG gives the following C-level recommendation:

“Clinicians may include previous treatment, number of sprains, pain level, and self-report of function in their evaluation, as well as an assessment of the sensorimotor movement systems of the foot, ankle, knee, and hip during dynamic postural control and functional movements, because of their role in influencing the clinical course and estimation of time to accomplish the goals of an individual with chronic ankle instability.” If you’re wondering exactly what that would look like, I would think about things like proprioceptive and balance testing on the involved and uninvolved side since this is potentially centrally mediated for the sensorimotor piece, and things like hop testing and Y or star balance for those functional and dynamic control pieces. Again, we don’t have specific measures that they recommend or cutoffs that tell us more about clinical course, but we’re pretty sure people who are worse on those kinds of tests in general are going to have an extended course.

Let’s talk diagnosis and classification. So first we’ll talk about acute lateral ankle sprain. This 2021 revision recommends classification in the acute lateral ankle sprain with a history of sudden onset with an ankle inversion-related injury, negative ottawa ankle rules, positive reverse anterolateral drawer test, positive anterolateral talar palpation test, and positive anterior drawer test. Traditionally I think we all would have just thought of the anterior drawer to test the ATFL and the talar tilt test to test the CFL which are typically the two potentially involved in an ankle sprain, but newer studies have found superior sensitivity and accuracy of the reverse anterolateral drawer test and anterolateral talar palpation than the traditional anterior drawer for assessing the ATFL. 

The reverse anterolateral drawer test is “reverse” because it is trying to glide the distal tibia and fibula posteriorly on the talus rather than translating the talus anteriorly. The examiner bends the patient’s knee and braces the heel against the table. Using one hand you put the ankle in about 10-15 deg of plantarflexion and what they call ‘unconstrained internal rotation’ and palpate the anterolateral talus to detect motion. The other hand grasps the distal tibia and fibula just above the talocrural joint and drives it posteriorly. A positive test noted with greater motion on the involved than the contralateral side. 

The anterolateral talar palpation test test is pretty much just the anterior drawer test, but the examiner palpates the lateral aspect of the talar dome during the test to assess how much anterior translation of the talus occurs. Oddly enough, while the anterolater talar palpation test had better sensitivity than the anterior drawer, it was not as specific. The traditional anterior drawer had poor sensitivity, but perfect specificity. This is probably why they chose to include both tests even though they are a variation of the same test. So do the test with palpating the talus and without and you should be in good shape. 

Put this together and you have a B level recommendation that clinicians should use special tests including the RALDT, anterolateral talar palpation and the traditional anterior drawer in addition to thorough history and physical examination to aid in the diagnosis of a lateral ankle sprain.

For diagnosis of Chronic ankle instability we are working to have a specific international recognized criteria for identifying chronic ankle instability, but we aren’t there yet. They recommend using the following: history of at least 1 significant ankle sprain, reports of “giving way” or instability, episode of a subsequent sprain and/or perceptions of ankle instability, decreased performance on functional performance tests, and scores on the following discriminate instruments. A score of 11 or greater on the Identification of Functional Ankle Instability or the IdFAI; a Cumberland Ankle Instability Tool score of 25 or less; and/or 4 or more answers of “yes” on the Ankle Instability Instrument. Let’s repeat that: IdFAI score of 11 or GREATER; CAIT score of 25 or less, and 4 or more yes’s on the AII. Some of the functional performance tests used include the side hop, timed hop, multiple hop, and the foot-lift test, as well as the Star Excursion Balance Test—specifically the medial, posteromedial, and anteromedial directions. All together that’s a B level recommendation for using reliable and valid discriminate instruments such the above as well as a battery of functional performance tests.  

Differential diagnosis

Let’s talk about differential diagnosis and imaging. The Ottawa ankle rules are likely the most important and likely information to come up on the exam from this section regarding acute ankle sprains. You should know these like the back of your… feet. Of note, the original CPG advocated using the Ottawa rule OR the Bernese ankle rules, but more recent research has shown less than optimal sensitivity for the Bernese rules; and as a screening tool, we know we want VERY HIGH sensitivity. So it is now not recommended unless using along with Ottawa ankle rules. I’m going to say don’t worry about knowing the Bernese rules. For the Ottawa rules, any of the following will warrant referral for radiographs, and radiographs specifically, not MRI or CT unless it is pertinent based on radiographic findings. 

-    Inability to bear weight and take 4 steps immediately after injury or in the emergency department. And do note, this is immediately after OR in emergency department. So if they could not bear weight and take 4 steps right after, but can in the ED, this is negative

-    Tenderness to palpation along the posterior edge or tip of the medial or lateral malleolus. For both, it is specifically the tip or the posterior edge along the distal most 6cm of the bone. Not the anterior aspect because especially with the lateral malleolus, this likely will be tender due to soft tissue injury, but that won’t mean there is a fracture.

-    Next is tenderness to palpation to the navicular

-    And finally tenderness to palpation at the base of the 5th metatarsal. 

The authors do note that ability to bear weight alone is not enough to rule out fracture, and decreases sensitivity from nearly perfect down to 88% if you do not use the palpation pieces. 

This covers the most common fracture sites associated with an ankle injury, but there are other very common either concomitant or isolated pathologies that could be present. Beyond fracture, I think the most important is being able to differentiate a syndesmotic injury also known as “high ankle sprain” from a typical lateral ankle sprain, whether it is the isolated injury or occurred along with lateral ligamentous injury. A syndesmotic injury more commonly will happen with a hyperdorsiflexion and external rotation of the foot than with an inversion injury due to this motion spreading the mortise apart and gapping between the tibia and fibular. Think about a planted foot where the lower leg is internally rotated and/or flexed forward forcefully. The location of pain, swelling, and or bruising is going to be about a centimeter or two higher at the distal tibiofibular joint, rather than between the distal fibula and talus. The best test we have for syndesmosis injury is the squeeze test, where you squeeze the distal fibula and tibia together above the malleoli, which in a positive test will reproduce pain. 

 For Chronic ankle instability, there is a very tangible list of things to look for that could be causing someone to still have pain or instability over a year following initial injury. Lookout for:

-    Ankle impingement

-    Fibularis muscle or tendon pathology

-    Osteochondral lesions

-    Synovitis

-    Bear in mind there could be: Chondral lesions

-    Bony or avulsion fragments creating impingement or loose bodies in the joint

-    Syndesmotic injury

-    Arthritis

-    Bifurcate ligament injury

-    Or symptomatic accessory ossicles, such as os trigonometry syndrome

For imaging in these cases, they note that the ACR appropriateness criteria say that when symptoms persist for more than 6 weeks, radiographs are usually appropriate, and that if they are negative but instability, impingement, osteochondral or tendon injuries are suspected, an MRI without contrast is usually appropriate. So not a super clear guideline here, but I think you can safely say that if you were to be given a case that fits either a later subacute (greater than 6 weeks) or chronic ankle instability presentation that has never gotten imaging, especially if they were to not get better with treatment, you should refer for radiographs and if those are negative and something else is fishy, go ahead for MRI without contrast. There is also a little bit about diagnostic ultrasound, which we know is growing in popularity, just know that it can be reliable and accurate for diagnosing ATFL and CFL injuries, and can even be accurate in identifying fifth metatarsal, and lateral and medial malleolus fractures. Still, go for radiographs. 

Let’s knock out what remains for the exam section, beginning with outcome measures. 

There is A-level recommendation to use the Foot and Ankle Ability Measure and the LEFS, and they update the 2013 recommendation to include the PROMIS or patient reported outcomes measure information system physical function or PF scale and the pain interface or PI scale. These can be used with acute lateral ankle sprain or chronic ankle instability patients. Just a refresh. The FAAM is as it sounds an ABILITY measure so higher scores mean higher function. It’s usually converted to a percentage of function so the MCID is 8% for the ADL sub scale and 9% for the sports sub scale. The LEFS again is a FUNCTION scale, not a disability measure, so higher scores mean higher function, and it has an MCID of 9 points. Sorry to give you percentages for one and points for another, but that’s how it’s reported. Don’t worry about MCIDs and all that for the PROMIS scales, but higher scores on the PF scale mean better function.  

There is also a C-level recommendation for the use of other measures to capture psychological status such as fear or anxiety about reinjury, kinesiophobia, and fear avoidance. For acute and post-acute lateral ankle sprain clinicians may use the Pain Self-efficacy Questionnaire, and for folks with chronic ankle instability you may use the shortened Tampa Scale of Kenesiophobia also known as the TSK-11, and the FABQ. For both of them, higher scores are going to indicate worse fear of movement fear avoidance and fear avoidance respectively. Don’t worry about MCIDs and all that for these. 

For physical impairment measures, there is A-level recommendation to assess and document ankle swelling, ROM (especially dorsiflexion, specifically using the weight bearing lunge test), Talar translation, tala inversion, and single leg balance (specifically using single leg balance on firm surface with eyes closed for static balance, and for dynamic balance using the star excursion balance test anterior, anteromedial, posteromedial, and postrolateral reach directions. All of this is for any of our groups, acute, post-acute, or chronic ankle instability. 

 There is also a C-level recommendation that you may also assess and document hip abduction, extension and external rotation strength for chronic ankle instability. Both of these recommendations are to be done at baseline and 2 or more times over an episode of care.  

For physical impairment measures, there is a B-level recommendation for using reliable measures of activity limitation, participation restriction, and symptom reproduction at baseline and 2 or more times during an episode of care with lateral ankle sprain or chronic ankle instability. The most specific they get is that you should specifically include measures of single-limb hopping under timed conditions when appropriate.

 In interest of time, we’ll go ahead an end there for this episode and pick up with interventions on our next episode where there will be a lot more fun information and strong recommendations.