Which Oxford Knee Score level represents a satisfactory symptom state after undergoing a total knee replacement?

Abstract

Background and purpose — Meaningful interpretation
of postoperative Oxford Knee Score (OKS) levels is challenging.
We established Patient Acceptable Symptoms State
(PASS) and Treatment Failure (TF) values for the OKS in
patients undergoing primary total knee replacement (TKR)
in Denmark.

Patients and methods — Data from patients undergoing
primary TKR between February 2015 and January 2019
was extracted from the arthroplasty registry at the Copenhagen
University Hospital, Hvidovre in Denmark. Data
included 3, 12, and 24 months postoperative responses to the
OKS and 2 anchor questions asking whether they considered
their symptom state to be satisfactory, and if not, whether
they considered the treatment to have failed. PASS and TF
threshold values were calculated using the adjusted predictive
modeling method. Non-parametric bootstrapping was
used to derive 95% confidence intervals (CI).

Results — Complete 3, 12, and 24 months postoperative
data was obtained for 187 of 209 (89%), 884 of 915 (97%),
and 575 of 586 (98%) patients, with median ages from 68 to
70 years (59 to 64% female). 72%, 77%, and 79% considered
as having satisfactory symptoms, while 6%, 11%, and
11% considered the treatment to have failed, at 3, 12, and 24
months postoperatively, respectively. OKS PASS values (CI)
were 27 (26–28), 30 (29–31), and 30 (29–31) at 3, 12, and 24
months postoperatively. TF values were 27 (26–28) and 27
(26–29) at 12 and 24 months postoperatively.

Interpretation — The OKS PASS values can be used to
guide the interpretation of TKR outcome and support quality
assessment in institutional and national registries.