Influence of Ankle Mobility on Knee Stability and Control

The step down test is an important Physical Therapy test to determine the ability of our athletes to stabilize their lower extremity in single leg stance.  Proper performance of this test requires adequate strength, balance, control, and mobility in the lower extremity.  Often athletes with lower extremity or spinal pain have a significant asymmetry in their ability to perform the test between their uninvolved and involved extremity.  I often find this test helpful to identify patients with knee pain who are unable to control their knee at foot strike.  Often the knee will travel inward toward the opposite leg with a compensatory pelvic drop (see below).  This indicates a lack of strength and/or poor biomechanics in the kinetic chain.  In addition to motor performance the step down test also offers important information on the ankle's ability to flex.

Ankle dorsiflexion, bending, is a crucial component of an athletes ability to perform.  Inadequate dorsiflexion can lead to poor mechanics up the lower extremity influencing pain patterns throughout the lower quarter.  Often I find restoration of an athlete's ankle dorsiflexion through manual therapy and exercise immediately improves their pain and performance on the step down test.  A recent article in the journal Manual Therapy supports the importance of the ankle on lower quarter control (Bell-Jenje et al. 2016).

The authors assessed 30 healthy females to determine the association between a loss of ankle mobility and the inward movement of the knee on a step down test.  Each participant's ankle mobility was measured and the performed the step down in two conditions: one with the foot flat and one with the heels elevated (see picture).  

Consistent with our clinical findings at Mend, the authors noted athletes with decreased ankle mobility demonstrated greater amounts of knee movement during the first test.  Interestingly, the poor mechanics were immediately improved when the participants performed the second test with the heel elevated.  This study highlights the importance of assessing the ankle in individuals with pain or poor performance on the step down test.