The modified Thomas test demonstrated moderate reliability among examiners during goniometer scoring and poor reliability during pass/fail scoring.
Measurement error during goniometer evaluation may have resulted in an overemphasis of the difference in test-retest scores for each examiner.
The modified Thomas test may not demonstrate a high level or reliability even when experienced examiners with similar education and training and with advanced orthopaedic assessment skills use it to assess flexibility of the rectus femoris muscle about the knee joint.
The clinical reliability of the modified Thomas test may be influenced by many factors that include but are not limited to variations in the application of assessment criteria, the scoring method used, the consistency and accuracy of surface landmarking, the patient population, and examiner experience.