Navicular Position Test: Understanding Arch Collapse, Procedure, and Clinical Significance

What is Navicular Position Test?

The Navicular Position Test, often referred to as the Navicular Drop Test, is a common clinical assessment used to measure the change in height of the navicular bone from a non-weight-bearing to a relaxed weight-bearing position, providing insight into the integrity and dynamic function of the medial longitudinal arch of the foot.

Understanding the Navicular Bone and Foot Arch

The navicular bone is a boat-shaped tarsal bone located on the medial side of the foot, situated between the talus and the cuneiform bones. It is a key component of the medial longitudinal arch (MLA), the primary arch of the foot responsible for shock absorption, weight distribution, and efficient propulsion during gait. The MLA is supported by bones, ligaments, and muscles, and its ability to flatten and recoil is crucial for healthy foot and lower extremity function.

Purpose of the Navicular Position Test

The primary purpose of the Navicular Position Test is to quantify the degree of pronation (flattening) of the medial longitudinal arch when the foot transitions from a non-weight-bearing to a weight-bearing state. Specifically, it aims to:

• Assess Arch Integrity: Provide a simple, objective measure of the foot's arch height and its dynamic collapse under load.
• Identify Excessive Pronation: Detect abnormal or excessive pronation, a common biomechanical fault often associated with various lower extremity dysfunctions and injuries.
• Guide Clinical Interventions: Inform decisions regarding orthotic prescription, footwear choices, and targeted exercise programs.
• Monitor Progress: Track changes in arch stability over time in response to interventions.

How the Test is Performed

Performing the Navicular Position Test requires minimal equipment and a clear understanding of anatomical landmarks.

• Equipment Needed:

  • Ruler (preferably with millimeter markings)
  • Pen or marker
  • A flat, firm surface

• Patient Positioning: The individual should first be seated comfortably with their foot flat on the floor, ensuring the subtalar joint is in a neutral or unweighted position. Subsequently, they will stand in a relaxed, weight-bearing posture.

• Procedure Steps:

  1. Locate the Navicular Tuberosity: Palpate the most prominent bony protrusion on the medial side of the midfoot. This is the navicular tuberosity.
  2. Mark the Navicular Tuberosity: Use a pen or marker to place a small dot on the skin directly over the identified navicular tuberosity.
  3. Measure Non-Weight Bearing Height: With the individual still seated and the foot relaxed on the floor (or slightly offloaded), measure the vertical distance from the marked navicular tuberosity to the floor using a ruler. Record this measurement (e.g., in millimeters).
  4. Transition to Weight Bearing: Ask the individual to stand up naturally, distributing their weight evenly on both feet, allowing their feet to adopt a relaxed, natural arch position. Do not allow them to actively "hold up" their arch.
  5. Measure Weight-Bearing Height: While standing, again measure the vertical distance from the same marked navicular tuberosity to the floor. Record this measurement.
  6. Calculate the Navicular Drop (ND): Subtract the weight-bearing height from the non-weight-bearing height.
     • Navicular Drop (ND) = Non-Weight Bearing Height - Weight-Bearing Height

Interpreting the Results

The calculated Navicular Drop (ND) value indicates the amount of arch collapse that occurs when the foot bears weight.

• Normal Navicular Drop:
  • Generally, a navicular drop of 6-8 millimeters (mm) is considered within the normal range for healthy individuals. This represents the natural, elastic flattening of the arch that occurs during weight bearing for effective shock absorption.
• Excessive Navicular Drop:
  • A drop greater than 10 mm (some literature suggests 10-15 mm as a threshold) is typically indicative of excessive pronation or a "collapsed" medial longitudinal arch. This suggests hypermobility of the foot and ankle joints and potentially reduced intrinsic foot muscle strength.
• Reduced Navicular Drop:
  • A drop of less than 6 mm may suggest a rigid or supinated foot type. While less common, a foot that doesn't adequately pronate can also lead to issues due to poor shock absorption and altered load distribution.

Clinical Significance and Implications

The results of the Navicular Position Test can have significant clinical implications, particularly when integrated into a comprehensive biomechanical assessment.

• Association with Injuries: Excessive navicular drop is frequently associated with an increased risk of various lower extremity musculoskeletal injuries, including:
  • Plantar fasciitis
  • Medial tibial stress syndrome (shin splints)
  • Patellofemoral pain syndrome
  • Achilles tendinopathy
  • Bunions
  • Stress fractures in the foot or tibia
  • Lower back pain (due to compensatory movements up the kinetic chain)
• Gait Mechanics: Excessive pronation can alter the entire kinetic chain, affecting knee tracking, hip rotation, and even spinal alignment during walking and running.
• Treatment Planning: Understanding the degree of navicular drop helps clinicians:
  • Prescribe appropriate orthotics (custom or over-the-counter) to support the arch.
  • Recommend specific strengthening exercises for the intrinsic foot muscles, tibialis posterior, and hip abductors.
  • Advise on suitable footwear that provides adequate support.
  • Guide gait retraining strategies.

Limitations and Considerations

While the Navicular Position Test is a widely used and practical tool, it's important to acknowledge its limitations:

• Static Measure: It provides a static snapshot of arch collapse and does not fully represent the dynamic function of the foot during activities like running or jumping.
• Inter-Rater Variability: The accuracy of locating the navicular tuberosity and consistent measurement can vary between different examiners.
• Not a Standalone Diagnostic: The test should never be used in isolation to diagnose a condition. It is one piece of information that contributes to a broader clinical picture alongside patient history, symptom presentation, and other physical examinations.
• Individual Variation: Normal foot structure and function can vary significantly among individuals.
• Lack of Universal Norms: While general guidelines exist, precise "normal" values can vary slightly across different research studies.

Who Uses the Navicular Position Test?

This test is a staple in the clinical assessment toolkit for a variety of healthcare and fitness professionals, including:

• Physical Therapists: To assess foot mechanics in patients with lower extremity pain or injuries.
• Athletic Trainers: To screen athletes for biomechanical risk factors that could predispose them to sports-related injuries.
• Kinesiologists and Exercise Physiologists: To understand foot function and tailor exercise programs or footwear recommendations.
• Podiatrists: As part of a comprehensive foot and ankle examination.
• Chiropractors: To assess lower extremity contributions to spinal alignment and posture.

Conclusion

The Navicular Position Test is a straightforward, non-invasive, and valuable clinical tool for assessing the static stability and dynamic collapse of the medial longitudinal arch of the foot. By quantifying the "navicular drop," clinicians and fitness professionals gain crucial insights into an individual's foot biomechanics, helping to identify potential risk factors for injury, guide appropriate interventions, and ultimately improve lower extremity function and overall musculoskeletal health. It serves as an important component of a comprehensive assessment, contributing to a holistic understanding of how the foot interacts with the rest of the kinetic chain.