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Validation of the KOOS, JR: A Short-form Knee Arthroplasty Outcomes Survey - PubMed

Validation of the KOOS, JR: A Short-form Knee Arthroplasty Outcomes Survey

Stephen Lyman et al. Clin Orthop Relat Res. 2016 Jun.

Abstract

Background: Medicare is rapidly moving toward using patient-reported outcome measures (PROMs) for outcomes assessment and justification of orthopaedic and other procedures. Numerous measures have been developed to study knee osteoarthritis (OA); however, many of these surveys are long, disruptive to clinic flow, and result in incomplete data capture and/or low followup rates. The Knee injury and Osteoarthritis Outcome (KOOS) physical function short-form (KOOS-PS), while shorter, ignores pain, which is a primary concern of patients with advanced knee OA.

Questions/purposes: Our objective was to derive and validate a short-form survey focused on the patient with end-stage knee OA undergoing TKA.

Methods: Using our hospital's knee replacement registry, we retrospectively identified 2291 patients with knee OA who underwent primary unilateral TKA and had completed preoperative and 2-year postoperative PROMs. We assessed 30 items from the 42-item KOOS that were quantitatively most difficult for patients to perform before TKA and qualitatively most relevant to patients with end-stage knee OA. Rasch analysis identified the KOOS, JR, a seven-item instrument, representing a single dimension, which we define as "knee health" because it reflects aspects of pain, symptom severity, and activities of daily living (ADL) including movements or activities that are directly relevant and difficult for patients with advanced knee OA. We assessed the internal consistency, external validity (versus KOOS and WOMAC domains), responsiveness, and floor and ceiling effects of the KOOS, JR. External validation was performed using calculated KOOS, JR scores in collaboration with a nationally representative joint replacement registry, the Function and Outcomes Research for Comparative Effectiveness in Total Joint Replacement (FORCE-TJR).

Results: Internal consistency for the KOOS, JR was high (Person Separation Index, 0.84; and 0.85 [FORCE]), external validity against other validated knee surveys was excellent (Spearman correlation coefficient, ρ 0.54-0.91), particularly for the KOOS pain (ρ 0.89 [95% CI, 0.88-0.91] Hospital for Special Surgery [HSS]; and 0.91 [95% CI, 0.90-0.93] [FORCE]) and KOOS ADL (ρ 0.87 [95% CI, 0.85-0.88] [HSS]; and 0.84 [95% CI, 0.81-0.87] [FORCE]). The KOOS, JR responsiveness (standardized response means, 1.79 [95% CI, 1.70-1.88] [HSS]; and 1.70 [95% CI, 1.54-1.86] [FORCE]) was high and floor 0.4-1.2%) and ceiling (18.8-21.8%) effects were favorable.

Conclusions: The new short knee PROM, the KOOS, JR, provides a single score representing "knee health" as it combines pain, symptoms, and functional limitations in a single score. This short-form PROM is patient-relevant and efficient.

Level of evidence: Level III, diagnostic study.

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Figures

Fig. 1
Fig. 1

The person-ability and item difficulty are shown. The horizontal line represents the measure of the variable in linear log units. The top bar graph locates each patient’s ability, with ability increasing from right to left. The bottom graph locates each item’s relative difficulty for this validation sample, with difficulty increasing from right to left. The numbers represent the thresholds between response categories. For data to adhere to the Rasch model, threshold points are correctly ordered, indicating patients have no difficulty consistently discriminating between response categories. KOOS, JR- 1 (Symptom) How severe is your knee joint stiffness after first wakening in the morning?; KOOS, JR- 2 (Pain) Twisting/pivoting on your knee; KOOS, JR- 3 (Pain) Straightening knee fully; KOOS, JR- 4 (Pain) Going up or down stairs; KOOS, JR- 5 (Pain) Standing upright; KOOS, JR- 6 (ADL) Rising from sitting; KOOS, JR- 7 (ADL) Bending to floor/pick up an object.

Fig. 2
Fig. 2

The standardized response means of knee replacement outcomes measures at preoperative baseline and 2 years after surgery are shown. KOOS-PS = KOOS physical function short-form; QOL = quality of life; ADL = activities of daily living; HSS = Hospital for Special Surgery; FORCE = Function and Outcomes Research for Comparative Effectiveness; SRM = standardized response mean.

Fig. 3
Fig. 3

A comparison of external validity of the KOOS, JR against nine other patient-reported outcome measures using the Spearman correlation coefficient is shown. HSS = Hospital for Special Surgery; FORCE = Function and Outcomes Research for Comparative Effectiveness; ADL = activities of daily living; QOL = quality of life; KOOS-PS = KOOS physical function short-form.

Fig. 4A–B
Fig. 4A–B

(A) Floor and (B) ceiling effects for 10 patient-reported outcome measures are shown. HSS = Hospital for Special Surgery; FORCE = Function and Outcomes Research for Comparative Effectiveness; ADL = activities of daily living; QOL = quality of life; KOOS-PS = KOOS physical function short-form.

Fig. 5A–B
Fig. 5A–B

The contour maps show the KOOS-pain domain versus the (A) KOOS, JR at baseline and (B) the change in score from baseline to 2 years after  THA. A scatterplot overlays a contour plot based on bivariate kernel density estimation. A bandwidth multiplier of one was used for each kernel density estimate. Areas of high density correspond to areas where there are many overlapping points. The scatterplot shows the positive correlation between the KOOS, JR (x-axis) and the KOOS pain domain (y-axis) at baseline and the change between baseline and 2-year followup.

Fig. 6A–B
Fig. 6A–B

The contour maps show the KOOS-ADL domain versus the (A) KOOS, JR at baseline and (B) the change in score from baseline to and 2 years after THA. In the figure, a scatterplot overlays a contour plot based on bivariate kernel density estimation. A bandwidth multiplier of one was used for each kernel density estimate. Areas of high density correspond to areas where there are many overlapping points. The scatterplot shows the positive correlation between the KOOS, JR (x-axis) and the KOOS ADL domain (y-axis) at baseline and the change between baseline and 2-year followup. ADL = activities of daily living.

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