Longitudinal and cross-sectional validity of the DynaPort® Knee Test in adults with nontraumatic knee complaints in general practice

Objective: The aim of the study was to determine the cross-sectional and longitudinal validity of a performance-based assessment of knee function, DynaPort®KneeTest (DPKT), in first-time consulters with nontraumatic knee complaints in general practice. Methods: Patients consulting for nontraumatic knee pain in general practice aged >18 years were enrolled in the study. At baseline and 6-months follow-up knee function was assessed by questionnaires and the DPKT; a physical examination was also performed at baseline. Hypothesis testing assessed the cross-sectional and longitudinal validity of the DPKT. Results: Eighty-seven patients were included for the DPKT, 86 were available for analysis. The studied population included 44 women (51.2%), the median age was 54 (range 18-81) years. At follow up, 77 patients (89.5%) were available for the DPKT. Only 3 out of 11 (27%) predetermined hypotheses concerning the cross-sectional and longitudinal validity were confirmed. Comparison of the general practice and secondary care population showed a major difference in baseline characteristics, DynaPort Knee Score, internal consistency, and hypotheses confirmation concerning the construct validity. Conclusion: The validity of the DPKT could not be demonstrated for first-time consulters with nontraumatic knee complaints in general practice. Measurement instruments developed and validated in secondary care are therefore not automatically also valid in primary care setting.