Arches of the Foot: Challenge of Mobility & Stability

                         

Arches of the Foot: Challenge of Mobility & Stability

Do you count your steps each day?  With the popularity of wearable devices to monitor our activity, many people have accepted the challenge to count their steps daily.  Various organizations have quantified the number of steps into categories:

• Low active is 5,000 to 7,499 steps per day
• Somewhat active is 7,500 to 9,999 steps per day
• Active is more than 10,000 steps per day.
• Highly active is more than 12,500.

The feet are where each of these steps begin.  There are 3 arches of the foot that provide both mobility and stability to ambulate.  The 3 arches include:

The function of the arches of the foot include:

• • • Weight distribution
    • Adapt to conversion of foot to rigid lever
    • Dampens shock of weight-bearing
    • Adapt to changes in support surface

This dichotomy of mobility and stability of the foot set it up for a variety of injuries.  There are at least 3 tests that can be used to assess varying types of mobility (or lack of mobility) of the ankle and foot.  The navicular drop, Coleman block, and windlass test will be discussed.

The navicular drop test assesses midfoot mobility.  The test has two steps: non-weight bearing and weight bearing.  Step #1:  Sitting with the foot on the floor, the clinician measures the distance from the navicular tuberosity to the floor. Step #2:  Standing with weight equally distributed on both feet, the clinician measures the distance between the same anatomic structures. 

It is normal for the navicular to drop in weight bearing.  A drop of 6 – 8 mm is considered normal and 10 – 15 mm is considered abnormal.  In addition, the navicular should drop the same amount in each foot.  Excessive navicular drop has been associated with shin splints, medial tibial stress fractures, and patellofemoral tracking abnormalities.  There is no published data on sensitivity or specificity of this test but reliability of the measure has been reported to range from 0.57 to 0.78.

The Coleman block test assesses hindfoot mobility as it relates to a plantarflexed first ray versus a tight tibialis posterior muscle.  While standing (#1), the clinician measures the alignment of the hindfoot, i.e. how much rearfoot varus or valgus.  Then, the client is asked to stand (#2) with on a 2 cm block under the lateral aspect of the foot (some suggest placing the block under the entire foot with the exception of the first ray- #3).

                  

The response of the hindfoot (varus/valgus) to standing on the block is observed.  If the hindfoot has less varus (moves towards valgus) when standing on the block, the hindfoot has adequate flexible and the problem is a plantarflexed first ray.  Whereas, if the hindfoot does not have less varus, the problem is limited hindfoot mobility attributed to tibialis posterior muscle tightness.  Although there is no statistical data on this test, the positioning and biomechanical process makes sense.

The Windlass test is used to assess the plantarfascia tension. There is a weight-bearing (WB) and non-weight-bearing (NWB) component to this test also.  In NWB, the ankle is stabilized in neutral and the great toe is dorsiflexed.  In WB, with equal weight on both feet, the great toe is again dorsiflexed.  Pain along medial longitudinal arch would be a positive test.  The statistics for this test reveals it is an exceptional diagnostic tool (sensitivity = 13.6 – 31.8%; specificity = 100%) with high reliability (0.96 – 0.99).

These 3 tests provide the clinician with information about the medial longitudinal arch and the structures that support it.  Based on the results of these tests, the patient might benefit from stretching, strengthening, or orthotic support.

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