KOOS Scoring. August 2012.

1

KOOS Scoring 2012

A change in how to manage missing items was introduced in 2012. Previously, 2

missing items were allowed in each subscale. From 2012, at least 50% of the items

should be responded to. This change is reflected in the updated Excel scoring file

formulae available from www.koos.nu. The differences in subscale level are outlined

in the following table:

Number of items needed

for calculation of

subscale score (2012

rule for missing items)

Number of items needed

for calculation of

subscale score (1998 rule

for missing items)

Pain 5 7

Symptoms 4 5

ADL 9 15

Sport/Rec 3 3

QOL 2 2

KOOS Scoring instructions

Assign the following scores to the boxes:

None Mild Moderate Severe Extreme

0 1 2 3 4

Each subscale score is calculated independently. Calculate the mean score of the

individual items of each subscale and divide by 4 (the highest possible score for a

single answer option). Traditionally in orthopedics, 100 indicates no problems and 0

indicates extreme problems. The normalized score is transformed to meet this

standard.

Missing data: If a mark is placed outside a box, the closest box is chosen. If two

boxes are marked, that which indicates the more severe problem is chosen.

As long as at least 50% of the subscale items are answered for each subscale, a

mean score can be calculated. If more than 50% of the subscale items are omitted,

the response is considered invalid and no subscale score should be calculated. For

the subscale Pain, this means that 5 items must be answered; for Symptoms, 4

items; for ADL, 9 items; for Sport/Rec, 3 items; and for QOL, 2 items must be

answered in order to calculate a subscale score. Subscale scores are independent

and can be reported for any number of the individual subscales, i.e. if a particular

subscale is not considered valid (for example, the subscale Sport/Rec 2 weeks after

total knee replacement), the results from the other subscale can be reported at this

time-point.

KOOS Scoring. August 2012.

2

KOOS Excel scoring files

Excel spreadsheets with formulae to calculate the five subscale scores are available

from www.koos.nu. If, for any reason, you prefer to use your own spreadsheets, the

Excel formulae are given below.

Excel formulation: When the raw data have been entered in the order the items

occur in the KOOS questionnaires available from koos.nu, these Excel formulations

can be copied and pasted directly into an English version of an Excel spreadsheet to

automatically calculate the five subscore scales. Please note that it has been

assumed that the items in the subscale symptoms appear first in the questionnaire.

KOOS Pain: =100-AVERAGE(I2:Q2)/4*100

KOOS Symptoms: =100-AVERAGE(B2:H2)/4*100

KOOS ADL: =100-AVERAGE(R2:AH2)/4*100

KOOS Sport/Rec: =100-AVERAGE(AI2:AM2)/4*100

KOOS QOL: =100-AVERAGE(AN2:AQ2)/4*100

KOOS Manual Score calculation

The slightly updated version of the formulae (presented above and used from August

2012 in the spreadsheets available from www.koos.nu) does not need any manual

imputation: Apply the mean of the observed items within the subscale (e.g. KOOS

Pain), divide by 4, and multiply by 100; when this number is then subtracted from

100, you have the KOOS subscale estimate for that particular cross-sectional

assessment of the individual patient. For manual calculations, please use the

formulae provided below for each subscale:

1. PAIN 100−

™?? ™??? ™ ? ™ × ™?

?

= 𝐾𝑂𝑂𝑆 𝑃𝑎𝑖𝑛

2. SYMPTOMS 100−

™?? ™??? ™ ? ™ × ™?

?

= 𝐾𝑂𝑂𝑆 𝑆𝑦𝑚𝑝𝑡𝑜𝑚𝑠

3. ADL 100−

™?? ™??? ™ ? ™? × ™?

?

= 𝐾𝑂𝑂𝑆 𝐴𝐷𝐿

4. SPORT/REC 100−

™?? ™??? ™? ? ™? × ™?

?

= 𝐾𝑂𝑂𝑆 𝑆𝑝𝑜𝑟𝑡/𝑅𝑒𝑐

5. QOL 100−

™?? ™??? ™ ? ™ × ™?

?

= 𝐾𝑂𝑂𝑆 𝑄𝑂𝐿

KOOS Scoring. August 2012.

3

WOMAC - How to score from the KOOS

Assign scores from 0 to 4 to the boxes as shown above. To get original WOMAC

Scores, sum the item scores for each subscale. If you prefer percentage scores

in accordance with the KOOS, use the formula provided below to convert the

original WOMAC scores.

Transformed scale = 100 - actual raw score x 100

maximum score

WOMAC subscores Original score = sum of

the following items

Maximum score

Pain P5-P9 20

Stiffness S6-S7 8

Function A1-A17 68

KOOS Profile

To visualize differences in the five different KOOS subscores and change between

different administrations of the KOOS (e.g. pre-treatment to post-treatment), KOOS

Profiles can be plotted. The example from Nilsdotter et al. [17] shows KOOS profiles

prior to and at three time points following total knee replacement (TKR).