https://www.selleckchem.com/products/ei1.html MAIN OUTCOME MEASURES Infit and outfit statistics, item step difficulties, person ability parameters, category function, and item and test information functions. RESULTS Large ceiling effects were present in the KOOS and International Knee Documentation Committee subjective knee form. Of the 65 items examined in this study, 35 items showed poor measurement properties. Item step difficulty for the remaining 30 items ranged from -5.45 (least difficult) to 0.57 logits (most difficult). The 5-category response options did not function well. Measurement precision decreased significantly as ability score increased beyond 0.30 logits. CONCLUSIONS Despite their use in clinical practice, several items showed poor measurement properties. Future studies are needed to develop and evaluate novel items that are suitable for measuring knee-related function in high-functioning populations to ensure continuity of PROMs as individuals recover from injuries.This longitudinal study investigated monthly motor development and physical activity (PA) of infants with and without Down syndrome. Gross and fine motor skills (Bayley Scales of Infant Development-III) and PA (accelerometer) were assessed in 35 infants at eight time points during infancy. A multivariate mixed model identified time points when motor scores diverged between the groups. In infants with Down syndrome, bivariate correlations between monthly PA and motor changes were calculated, and multivariate analysis of variance probed the influence of early PA on motor-skill timing. indicate that differences in gross and fine motor skills first emerge at 2 and 4 months, respectively. In infants with Down syndrome, gross motor and PA changes between 4 and 6 months were positively correlated. Infants more active than the mean at 2 or 3 months achieved several prone and sitting skills earlier. These results highlight the adaptability of early infancy and the importance of early interventio