Sports Medicine Research: In the Lab & In the Field: Position Someone to Guard Against Bad Laxity Measures (Sports Med Res)


Wednesday, May 25, 2016

Position Someone to Guard Against Bad Laxity Measures

Examining Ankle-Joint Laxity Using 2 Knee Positions and With Simulated Muscle Guarding

Hanlon S, Caccese J, Knight CA, Swanik CB, & Kaminski TW.  J Athl Train, 2016; 51(2): 111-117. doi:10.4085/1062-6050-51.3.06

Take Home Message: Knee flexion to 90 degrees limits ankle laxity with the talar tilt test in comparison to a fully extended knee.  However, knee position has no effect on anterior drawer laxity. Muscle guarding will limit our ability to accurately assess ankle laxity with a talar tilt or anterior drawer test. 

The accuracy and reliability of special tests, such as the anterior drawer and talar tilt tests, can be affected by many factors, including muscle guarding, patient positioning, and clinician experience.  It is critical for clinicians to know how to properly perform these tests at the ankle to optimize test performance. The authors of this study compared ankle-joint laxity and muscle activity during these ligamentous ankle special tests at different knee positions. They also investigated how muscle guarding affects these tests.  The authors measured ankle laxity and muscle activity of the medial gastrocnemius in 33 healthy college students with their knee in 2 positions (i.e., extension & 90° of flexion).  To simulate a guarding condition, the authors asked participants to maintain a contraction of their tibialis anterior at 30% of their maximum voluntary contraction. The two special tests were standardized with an ankle arthrometer, which can perform the test with a standardized force and motion. The authors reported that knee position did not affect muscle activity nor anterior translation, but that the knee positioned in extension resulted in greater inversion/eversion motion than a flexed knee.  The researchers reported that there was a decrease in ankle motion during both tests and in both knee positions when participants simulated muscle guarding.

The findings of this study are interesting because the authors confirmed that a patient needs to be relaxed and not guarding against the laxity tests to get the best results.  It is important to try to find ways to limit muscle guarding when performing an ankle evaluation.  They also reported that knee position may affect the findings of the talar tilt, but not the anterior drawer test.  It would be interesting to see if the findings of these ankle laxity tests were similar at other knee positions, such as slight to moderate knee flexion.  Clinically, this may mean that we could position the patient to allow us to have an optimal line of pull for anterior translation without concern for knee position, but that we should have the knee in extension to assess talar tilt laxity.  It is surprising that there is greater inversion/eversion motion with the knee in full extension, and it would be interesting to see at what point of knee flexion does the motion start to become limited.  However, as clinicians we need to be cognizant of muscle guarding and knee position when we assess ankle laxity – it will only benefit us. 

Questions for Discussion:  How were you taught to position the knee when assessing ankle laxity?  What position works best for you when testing ankle laxity clinically?

Written by: Nicole Cattano
Reviewed by: Jeffrey Driban

Related Posts:
Diagnostic Accuracy of Clinical Tests for Ankle Syndesmosis Injury

Hanlon S, Caccese J, Knight CA, Swanik CB, & Kaminski TW (2016). Examining Ankle-Joint Laxity Using 2 Knee Positions and With Simulated Muscle Guarding. Journal of Athletic Training, 51 (2), 111-7 PMID: 26881870


KellyMartinUVA said...

I think this article assesses the need for accuracy when performing special tests around the ankle joint. All too often, clinicians find themselves assessing another ankle sprain, and will go through the motions in order to diagnose it. Muscle guarding is definitely a factor and should be taken into account. It is also intriguing that this article found that a talar tilt test should be performed with the knee in extension. This could potentially be incorporated into practice, and more research should be done to determine what the most optimal testing position is in order to gain both sensitive and specific results.

Nicole Cattano said...

Hi Kelly - thanks for your comment. I agree that these findings could be incorporated into clinical practice to help with our diagnostic capabilities. We need to position a patient to put their muscles at a disadvantage in the event that there is guarding. This reinforces the importance of patient positioning - just like the Lachman over the Anterior Drawer in the knee.

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