Navicular Drop Test (NDT)

What is the Navicular Drop Test (NDT)?

Imagine you're out for your regular morning jog. The sun is just beginning to rise, and the air is crisp and cool against your skin. You've been running for a few minutes when you notice a dull ache in your lower leg. It's not enough to stop you in your tracks, but it's there, nagging at you with every step. As you continue your run, you can't help but wonder: could this pain be a sign of something more serious?

This scenario is all too familiar for many runners, especially those who have experienced lower leg pain or sustained injuries while pursuing their passion for running. Whether it's shin splints, knee pain, or something more severe like stress fractures, understanding the underlying causes of these issues is crucial for both prevention and treatment.

One diagnostic tool sports physical therapists and clinicians often use is the Navicular Drop Test (NDT). This clinical test provides valuable insights into foot pronation and the dynamic navicular motion during activities like normal walking or running.

So, what exactly is the NDT? Essentially, it measures the amount of navicular drop, which is the difference in height of the navicular tuberosity from a neutral position to a weight-bearing position. This drop is indicative of how much the foot pronates during the stance phase of gait. While the NDT is widely used in clinical practice, it's essential to note that it's just one component of a comprehensive clinical assessment (Vinicombe et al., 2001).

Why does this matter? Well, excessive navicular drop or increased navicular drop has been identified as a risk factor for various lower extremity injuries, including medial tibial stress syndrome (shin splints), patellofemoral pain syndrome (front knee pain), and even ankle injuries such as stress fractures.

By assessing the navicular position before and during weight-bearing activities, clinicians can gain valuable insights into foot posture and function. This information not only helps identify individuals at risk of sustaining injuries but also guides treatment strategies, such as orthotic intervention or exercise programs.

Alternative techniques, such as the Feiss Line Test, can be used to determine the height of the medial arch using the navicular position. The Navicular Drop Test plays a significant role in the clinical assessment of foot posture and function, particularly in identifying individuals at risk of sustaining overuse injuries during physical activities like running. By understanding the dynamics of navicular motion and its relationship to foot pronation, clinicians can effectively intervene and support injured runners in their journey toward recovery and injury prevention.

How to conduct the Navicular Drop Test

Before you begin the Navicular Drop Test (NDT), you need to prepare two things: a non-permanent marker and a piece of paper.

The marker will record the measurements of the navicular drop on the piece of paper. A pen is fine, but we recommend using a marker instead because pens are sharp, and you don't want to accidentally prick or slash your patient.

Once you have those ready, do the following:

• Have your patient sit down first.
• Tell them to keep their legs and feet relaxed. Being relaxed should make their feet maintain an arch.
• Locate their navicular tuberosity on one foot and mark it with your non-permanent marker.
• Once you've marked the navicular tuberosity, have the patient stand up without applying weight to their foot. This means that their subtalar joint is neutral.
• While the subtalar joint is neutral, measure the height of the navicular bone. This measurement is the starting position. Make sure to use a piece of paper and mark the starting position on it.
• After that, have your patient put weight on their foot. Remeasure the height of the navicular bone and mark it on the piece of paper.
• Repeat all of this for the other foot.

And that's how you conduct the Navicular Drop Test (NDT)! Easy, huh?

How to interpret the findings of the Navicular Drop Test

After recording the measurements of the navicular bone in neutral and while the foot is bearing weight, the last thing you'll need to do is to calculate the difference between the two!

You will be measuring the difference by the millimeter. For the Navicular Drop Test, the foot is positive for overpronation if the difference is more than 10mm (1cm). This is not a diagnosis, though. If the foot is overpronated, the next step is to conduct a further examination. You will have to perform other foot-related physical examination techniques to determine if the patient is dealing with certain foot conditions like the ones mentioned earlier. If they test positive for those as well, imaging tests should be able to confirm things to make an official diagnosis.

Once you have an official diagnosis, you can determine how to treat your patient.

When is it best to conduct the Navicular Drop Test?

The best times to conduct the Navicular Drop Test (NDT) are the following:

Whenever a patient presents themselves during a consultation for foot problems

If they complain about problems with their feet, this is one of the standard physical examinations you can conduct to gauge the possible problem. If the results are positive, the next set of tests should deal with their Achilles tendon, heel, plantar fascia, etc. If their feet are overpronated, there might be a chance that they have issues related to those.

Taking a series of tests

Speaking of “the next set of tests,” it should always be included as part of a comprehensive examination because the Navicular Drop Test (NDT) alone is not enough to determine what foot problems the patient is dealing with. A positive test should be able to set the “roadmap” of tests to be conducted to narrow down the problem and make an official diagnosis. The collective results will then determine what goes into a patient's treatment plan.

Follow-up assessments

Naturally, you will want to know how your patient is doing after you've implemented a treatment plan. If overpronation is the cause of their foot problems, then you can repeat this test to see if the navicular drop length has lessened.

Who can conduct the Navicular Drop Test?

Since the Navicular Drop Test (NDT) is a physical examination of the foot, the healthcare professionals who can conduct this should be knowledgeable regarding assessing and treating foot-related ailments. These professionals include the following:

Podiatrists

These healthcare professionals specialize in diagnosing and treating problems related to the feet and ankles. They are trained in conducting physical examinations such as this, and because feet and ankles are the focus of their practice, you can trust that their interpretations and decisions are well-informed and backed by years of extensive training and experience.

Orthopedists

These professionals are well-versed in the musculoskeletal anatomy of people. While Podiatrists focus on the feet, these cover the feet and more. They can conduct this test and more, interpret the findings well from their tests and those from others, are equipped to make official diagnoses, and can implement treatment plans. If the patient requires surgery, orthopedic surgeons can perform surgical procedures to fix whatever the foot or ankle problem is.

Physical therapists and occupational therapists

These professionals can also conduct the Navicular Drop Test (NDT) and other physical examination techniques for assessing feet. They can also assist with creating a treatment plan by providing rehabilitation to restore the patient to tip-top shape.

What are the benefits of the Navicular Drop Test?

Plan early intervention

Let's say that you conducted the Navicular Drop Test (NDT), and the patient's results turned up positive for overpronation. Still, based on other examinations, the patient doesn't have any foot conditions as of now. You can take the opportunity to develop plans for early intervention so that the patient can manage their overpronated feet and restore them to normal. Doing so can prevent foot problems like Plantar Fasciitis from developing (or worsening if the problem is still mild).

Help healthcare professionals monitor their treatment plans

Earlier in this guide, we mentioned that one of the best times to conduct the Navicular Drop Test (NDT) is to monitor the patient's feet during routine check-ups. If the navicular drop length decreases, their foot pronation slowly becomes normal. That also means they're getting better. Repeating this test to monitor the patient also monitors the treatment plan. If the patient is getting better, it's safe to say that your treatment plan is going well! Cool! If not, you might want to make some changes and see if said changes are effective.

Create custom orthotic items

One of the possible treatments that you can give is to have an orthotic item created for the patient. What this item will be will depend on the foot or ankle problem that the patient is dealing with. Since the Navicular Drop Test is for the foot, specifically the arch, you can use the results to help create a custom orthotic foot pad to help patients maintain their foot arch while wearing shoes.

References

Vinicombe, A., Raspovic, A., & Menz, H. B. (2001). Reliability of navicular displacement measurement as a clinical indicator of foot posture. Journal of the American Podiatric Medical Association, 91(5), 262-268.