Why does the Joint Position Sense (JPS) test for the neck not account for speed of movement?

Why Speed of Movement Is Not Accounted for in the JPS Test for the Neck

The Joint Position Sense (JPS) test for the neck does not account for speed of movement because it is specifically designed to measure proprioceptive accuracy—the ability to perceive head position in space—rather than motor control or movement velocity, which are separate neuromuscular functions.

Core Purpose of the JPS Test

The JPS test fundamentally assesses cervicocephalic kinesthesia, which is the ability to perceive both movement and position of the head in space relative to the trunk 1. This test measures proprioceptive accuracy by quantifying the error when returning to either a neutral head position (NHP) or target head position (THP) following active neck movements 2.

• The test evaluates cervical afferent input to detect disturbances in sensorimotor control that may contribute to neck pain syndromes 3
• It specifically targets mechanoreceptors in the cervical spine that provide positional information 1
• The primary outcome is joint position error (JPE)—the angular deviation from the intended target position 2, 4

Why Speed Is Deliberately Excluded

Proprioception vs. Motor Control Are Distinct Systems

Speed of movement reflects motor control and neuromuscular coordination, not proprioceptive accuracy. Including speed would confound the measurement by introducing variables unrelated to position sense:

• Proprioceptive testing isolates the sensory system's ability to detect joint position 1
• Movement speed involves motor planning, muscle strength, coordination, and voluntary control—separate from position awareness 4
• Mixing these domains would make it impossible to determine whether errors stem from sensory deficits or motor dysfunction

Standardization and Reliability Concerns

The JPS test already demonstrates variable reliability across different movement directions and testing positions 2. Adding speed parameters would:

• Further reduce test-retest reliability by introducing additional sources of variability
• Make clinical interpretation more complex without clear evidence of added diagnostic value
• Require participants to perform movements at specific velocities, which is difficult to control without sophisticated equipment 2

What Speed-Related Testing Actually Measures

When studies do examine movement speed in neck pain populations, they are assessing different constructs:

• Reduced movement speed in people with neck pain reflects motor control deficits, pain avoidance behaviors, or fear of movement 4
• Five of 10 studies showed reduced movement speed in neck pain patients compared to controls, but this was analyzed separately from position sense 4
• Speed reduction indicates quality of motion impairment, not proprioceptive dysfunction 4

Clinical Implications and Testing Strategy

To comprehensively evaluate cervical sensorimotor dysfunction, multiple tests are required—JPE alone is insufficient:

• JPE testing should be combined with balance assessment and eye movement control tests (such as the smooth pursuit neck torsion test) 3
• An abnormal rotation cervical JPE score has high positive predictive value (88%) but low sensitivity (60%) and specificity (54%) for determining abnormalities in balance or eye movement control 3
• All three measures (JPE, balance, and eye movement) are necessary to identify disturbances in the postural control system in patients with persistent whiplash-associated disorders 3

Practical Testing Approach

When assessing neck proprioception clinically:

• Perform JPE testing at a comfortable, self-selected pace to isolate position sense without speed constraints 2, 5
• Test multiple movement directions (flexion, extension, left and right rotation) as reliability varies by direction 2
• Consider both sitting and standing positions, as reliability differs between postures 2
• Use absolute error (magnitude of deviation) and constant error (directional bias) as separate outcome measures 2

Common Pitfalls to Avoid

• Do not interpret slow movement during JPE testing as proprioceptive deficit—this reflects motor control or pain behavior, not position sense accuracy 4
• Do not rely solely on JPE to screen for sensorimotor dysfunction—weak-to-moderate correlations exist between JPE, balance, and eye movement control, requiring all three assessments 3
• Do not assume good reliability across all movements—JPE shows good reliability for some but not all movement directions, particularly in asymptomatic individuals 2