Validation of the movement system impairment-based classification in patients with knee pain

• Four factors related to MSI categories PLG, TFHypo and TFR were extracted.
• Recognizing 4 factors assigned evidences for the validity of the 3 MSI categories.
• Two new subscales of TFR category (TLR and FAdd/MR) were identified.
• A valid classification can be used to identify homogenous subgroups of knee problems.

BackgroundCategorizing patients with knee pain problems based on pathoanatomical sources has not proved to be the most effective method for directing physical therapy interventions. Movement system impairment (MSI) classification system may be an alternative in the assessment, diagnosis, and management of patients with knee pain. No previous study has been conducted to validate the proposed system in these patients.ObjectiveTo assess construct validity of the MSI classification system in patients with knee pain.DesignA cross-sectional methodological study.SettingRasul Akram Hospital.ParticipantsOne hundred eighty subjects with knee pain aged 18–65 years.MethodsThe MSI classification recognizes seven categories of knee pain problems based on the findings from the symptoms and signs assessment. Three physical therapists examined subjects with knee pain. A principal component analysis (PCA) was used to derive proposed categories. Eigenvalues and a scree plot were also used to determine the factor retention.ResultsFour factors related to three proposed categories were extracted from the PCA. Two factors were related to tibiofemoral rotation (TFR) category. The other two factors were related to proposed categories patellar lateral glide (PLG) and tibiofemoral hypomobility (TFHypo).ConclusionThe results provided evidence for the construct validity of three (TFR, PLG, and TFHypo) of the seven categories proposed by MSI classification. In addition TFR was subcategorized into two groups which were named as tibial lateral rotation (TLR) and femoral adduction/medial rotation (FAdd/MR) in the present study.