Predicting Outcomes After a Lateral Ankle Sprain

Nearly every time I've have a frustrated patient, it's a been from the difference in their expectations and the reality of their recovery. Much worse if I've predicted a much better outcome then they're experiencing.

So my focus when seeing a new patient, or tracking progress of their rehabilitation, is to set appropriate expectations, especially around likely timelines for recovery, return to running and return to sport.

One of my clinical practice axioms is always under promise and over deliver.

One of the things I've found most useful is rather than trying to nail down a specific time frame I expect them to recover in, I explain the return to sport criteria I'd use to decide when they're ready to run, start training again and return to play.

For many people understanding that there's objective markers and it's not a subjective decision, that it's not purely time based and there's movements and tests they can track their progress against, they find it easier to stay on track and deal with periods of slower progress in rehab as they can see their training is building towards being able to do faster, stronger and more skilful movements needed to safely return. (I have another post discussing return to play criteria post ankle sprain.)

That being said, we still need to give rough timelines. So what I do is utilise the traditional grading system to guide my rough prognosis (grade 1: 2-3 weeks, grade 2: 6-12 weeks, grade 3: 3-6 months+) and then consider factors that indicate they’re likely to stay on track or have a poorer outcome.

For many foot and ankle conditions, knowing what those factors are is purely through clinical experience/suspicion. However, in lateral ankle sprains we have a lot of research to help guide this discussion.

So here's the key pieces of information you can use to inform your prognosis.

What improves outcomes:

1. Early exercise intervention.
Following acute LAS, those who started exercise rehabilitation early had faster recovery, objective stability, subjective stability.
2. Training the whole lower limb.
Hip abduction and external rotation strength explains a significant amount of dynamic lower limb stability, an important predictor of recovery!
3. Addressing ankle joint motion deficits.
These also significantly impact dynamic balance and sport specific task performance, which are important for outcomes!

With these are shown to improve outcomes, it's also fairly safe to presume the inverse is true. Those who don't start rehabilitation early will likely have a longer recovery, and we know those who don't do any rehab have poorer short and long term outcomes.

What may indicate poorer outcomes.

1. Comorbid conditions delaying recovery - Get your diagnosis right!
It's really easy to diagnose an ankle sprain from history, a cursory palpation and a check of ottawa ankle rules to rule out fracture. However, this shouldn't be the extent of your assessment. In up to 92% of ankles sprains, another injury other than the ATFL will also have occurred. These can explain why some symptoms remain problematic well after the expected recovery time.

Catching other pathologies, especially tendon, talar dome and other ligament injuries, is essential to understanding injury prognosis, as well as being able to explain to patients why this will take longer than other sprains they may compare themselves to!

2. Immobilisation.
Some of those conditions require immobilisation for a period of time. There’s limited long term impact if this can be kept under 10 days, with long term recovery significantly impacted if they’re required to be in the boot for more than 4 weeks.
3. Age, BMI and prior ankle sprains.
Being older, having a higher BMI and previous ankle sprains are all predictive of worse outcomes overall. A larger body mass can be indicative of a larger injury as there’s more forces involved in the sprain.
4. Pain and swelling.
At initial testing, pain with weightbearing lunge and medial ankle joint line tenderness are associated with reduced function at 4 months post injury. These are indicative of an ankle joint/talar dome injury, which can significantly slow rehabilitation.

Time based markers:

1 week post injury:
There’s worse outcomes if the patient has significant pain when walking or can’t weightbear due to pain. More time to decondition, higher risk of time in a boot, potential for increased instability / reduced confidence with moving as it improves; all things that can slow recovery.

2 weeks post injury:
There’s an increased risk of developing chronic ankle instability (CAI) at 6 months post-injury in those who at week 2 post-injury can’t:
- Complete any jumping or landing tasks
- Have poor dynamic postural control (can be measured with mSEBT).
- Lower self reported function

These can be indicative of a higher severity ligament injury causing more instability, as well as more co-morbidities (repeating this message over and over), that can impact recovery and rehabilitation.

This can be a good point to discuss with patients directly. Longer recoveries can lead to lower motivation and rehab getting lost when life gets busy and good day to day function returns. Emphasising the need for rehab to reduce the risk of future CAI, more injuries, more rehab and future impacted function.

3 weeks post injury:
Effective coping strategies, not the severity of the injury is associated with fewer symptoms.

This is a good reminder that we should also be focused on patients psychological wellbeing post-injury. Ensuring they have a good support network, addressing any worries and concerns that can start to creep in and get assistance or refer on for people with kinesiophobia and catastrophization are essential parts of being a rehab provider.

2 months post injury:
Complete an Ankle Go Score. Those with a score <8 are significantly less likely to return to play at a similar level they were at prior to injury at 4 months, and those with a score of <=11 were significantly more likely to develop chronic ankle stability.

It's well worth familiarising yourself with the Ankle GO score. While it's not validated specifically for return to play criteria (yet - it was originally designed for this and research is on the way), it's got great utility at predicting future outcomes when measured at 2 months. I discuss this more here.

What isn't useful at predicting outcomes?

1. Anterior Drawer Testing.
Retesting at 6 weeks post injury is not an effective guide to recovery. The goal of therapy is to address strength and balance deficits, not quick decreases in laxity.

2. Imaging Results.
Whether it was a simple or complex sprain on imaging didn’t impact outcomes at 6 months. Which seems counterintuitive initially, but makes sense. Someone with a complex sprain and comprehensive rehabilitation will absolutely outdo someone who does a simple sprain and does nothing.

It's a great reminder for patients that they can have a lot more control on their outcomes.

References:

Martin RL, Davenport TE, Fraser JJ, Sawdon-Bea J, Carcia CR, Carroll LA, Kivlan BR, Carreira D. Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision 2021. J Orthop Sports Phys Ther. 2021 Apr;51(4):CPG1-CPG80. doi: 10.2519/jospt.2021.0302. PMID: 33789434.