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KOOS Scoring

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KOOS Scoring. August 2012.

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
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

KOOS Scoring. August 2012.

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−
™??   ™???   ™ ? ™? × ™?

4. SPORT/REC 100−
™??   ™???   ™? ? ™? × ™?
=  𝐾𝑂𝑂𝑆  𝑆𝑝𝑜𝑟𝑡/𝑅𝑒𝑐

5. QOL 100−
™??   ™???   ™ ? ™ × ™?

KOOS Scoring. August 2012.

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).