Forgotten Joint Score Post Total Knee Arthroplasty and Its Correlation with the New Knee Society Score

Indian J Orthop. 2021 Jul 17;55(5):1175-1179. doi: 10.1007/s43465-021-00452-z. eCollection 2021 Oct.


Background/purpose: Forgotten Joint Score (FJS) is designed to asses patient recovery post Total Knee Arthroplasty (TKA) in a new dimension. It assess the ability to forget the operated joint as artificial during activities of daily living. New Knee Society Score (NKSS) is developed to encompass objective and subjective outcome as well as an assessment of patient expectation and satisfaction. Our purpose was (1) to determine FJS at 1 year post TKA in Indian Patients, and (2) to assess convergent validity between FJS and the NKSS. We hypothesised that FJS should strongly correlate with the Satisfaction (SS) and Knee perception(KPS) sub-component of NKSS.

Methods: We enrolled 181 patients who underwent primary TKA during an 8-month duration. They were prospectively followed up at 1-year review clinic when FJS and NKSS were administered. 169 patients completed the assessment forms and 13 patients were lost to follow-up. Statistical evaluation was done with Spearman correlation test.

Results: Mean FJS at 1 year was 66.6 ± 25.9 with 14% ceiling and 1% floor effects. There was a mild to moderate correlation of FJS with NKSS (p < 0.001, r = 0.47) and its sub-scores (p < 0.001; r = 0.43 and r = 0.44). There was a weak correlation of FJS with NKSS sub-components of SS and KPS (p < 0.001; r = 0.37 and 0.25, respectively).

Conclusion: Mean FJS at 1 year post TKA showed convergent validity with NKSS; however, the correlation was not strong enough to use them interchangeably. Hypothesis that FJS should strongly correlate with the NKSS sub-components of satisfaction and joint perception was refuted. We conclude, FJS provides unique evaluation in recovery post TKA, different from NKSS.

Level of evidence: Level III.

Keywords: Convergent validity; Forgotten Joint Score; Knee Arthroplasty; New Knee Society Score; Results.