To translate and validate the Kujala Anterior Knee Pain Scale (AKPS) in patients who have undergone total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) and evaluate the internal consistency, construct validity and ceiling or floor effect.
After standard forward and backward translation was performed, 302 patients who have received a TKA or UKA filled out the AKPS together with Hospital for Special Surgery (HSS) patella score, visual analogue score (VAS) for pain, the Oxford 12-item questionnaire and the SF-36 at follow-up. The internal consistency was tested using Cronbach's α coefficient. The construct validity was assessed using Spearman's rank correlation (R) to test for correlations between the AKPS and VAS HSS, HSS patella score, VAS month, Oxford 12-item questionnaire and SF-36 subscales. Ceiling or floor effects are given in percentage of patients giving a maximum or minimum score.
The internal reliability of the AKPS is acceptable with a Cronbach's α of 0.81 in patients after TKA or UKA. A high correlation was found between the AKPS and the Oxford 12-item questionnaire (R = 0.81). Moderate correlations were found with the VAS month (R = 0.63), HSS patella score (R = 0.51) and SF-36 subscales physical functioning (R = 0.59), role-physical (R = 0.59), bodily pain (R = 0.57). Other correlations were poor, therefore indicating a good convergent and divergent validity. Ceiling effects were observed for the HSS patella score (31 %), VAS HSS (51 %), VAS pain (19 %), SF36-RP (46 %), SF36-RE (80 %) and SF36-BP (24 %). No ceiling or floor effect was found for the AKPS, Oxford 12-item and the other SF36 domains.
The AKPS appears to be reliable and valid in patients after knee arthroplasty, with no ceiling and floor effects, and can be used to assess anterior knee pain in patient who underwent joint replacement surgery.