Development of a scale to assess performance following primary total knee arthroplasty

Quantitative assessment of postsurgical knee motion provides sensitive measurements, but results are technical and may not be meaningful to patients. Although several knee-specific instruments exist, no patient-reported outcome (PRO) measure correlates function with improved stability, motion, satisfaction, and confidence.

To address both the above limitations by developing a PRO measure to assess the phenomenon of a "normal" knee after primary total knee arthroplasty (TKA).

A draft conceptual model linking the impact of clinical mechanics to hypothesized functional outcomes was generated after a literature review of available assessment tools. Participants aged 18 to 80 years having undergone TKA within the past 10 to 18 months were identified and screened by clinical sites to participate in phase 1 focus groups or phase 2 in-depth interviews. Participants were asked to describe their TKA experiences, including how their knee feels now, followed by cognitive debriefing of Patient's Knee Implant Performance (PKIP) draft items.

Phase 1 results indicated that concepts of confidence, stability, and satisfaction in patients' replacement knee when performing certain activities were distinct and important in the patients' assessment of their TKA. Phase 2 efforts yielded a final version of the PKIP measure containing nine items assessing the broader concepts of stability, confidence, and satisfaction in association with activities. Presurgical and postsurgical versions of the measure were created.

Results of this qualitative study support use of the PKIP as a complementary PRO measure to assess performance after primary TKA. Psychometric evaluation of the PKIP is planned.