Accuracy and reliability of knee goniometry methods

Area of Science:

• Orthopedics
• Biomechanics
• Medical Measurement Technology

Background:

• Accurate measurement of knee range of motion is crucial for clinical examination and post-operative assessment.
• Various tools exist for measuring knee angles, including goniometers, smartphone applications, and digital inclinometers.
• Establishing the minimum significant difference between measurement methods is vital for monitoring changes effectively.

Purpose of the Study:

• To evaluate the reliability and minimum significant difference of different methods for measuring knee range of motion.
• To compare visual estimation, short and long arm goniometers, a smartphone application, and a digital inclinometer.
• To determine the most accurate method for knee angle assessment.

Main Methods:

• Knee angles were measured by three distinct users (orthopaedic surgeon, surgical trainee, physiotherapist).
• Five methods were employed across six knees, assessing three angles plus full active flexion and extension.
• Measurements were repeated with users blinded to previous results, totaling 300 measurements.

Main Results:

• All methods demonstrated high inter-rater and intra-rater reliability (all > 0.99 and > 0.98, respectively).
• The digital inclinometer exhibited the highest accuracy with a minimum significant difference of 6°.
• Visual estimation and short arm goniometry were the least accurate, with a minimum significant difference of 14°.

Conclusions:

• The digital inclinometer is the most accurate tool for measuring knee angles.
• The long arm goniometer is the second most accurate method.
• Visual estimation and short arm goniometry lack the accuracy required for reliable knee angle assessment.