263scores representing better function. All items must have a response in order to calcu-
late a total score (i.e., no missing items). The KOOS-PS and HOOS-PS are available
free of charge in a number of language versions ( http://www.koos.nu ).
The KOOS-PS and HOOS-PS provide short, quick measures of physical func-
tion, which reduces the likelihood of missing items. They do not have any fl oor or
ceiling effects, meaning that they can detect deterioration or improvement in a
patient’s condition. The KOOS-PS is responsive to physical therapy, pharmacologi-
cal interventions, and total knee replacement, whereas the HOOS-PS is responsive
to changes following pharmacological interventions and total hip replacement in
patients with hip OA. Responsiveness to other interventions is unknown.
Similar to the longer formats, a limitation of the physical function short forms is
their reliability for use in individual patients. Although both are suffi ciently reliable
for use in groups of patients, the HOOS-PS has confl icting fi ndings regarding test–
retest reliability in patients with hip OA, whereas the KOOS-PS does not demon-
strate adequate reliability for use in individual patients. Changes in an individual
patient’s KOOS-PS score of greater than 18.6 points represents a real change [ 31 ],
but this has not been determined for HOOS-PS.
Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP)
An OARSI/OMERACT initiative, the ICOAP was designed to comprehensively
capture the pain experience of patients across the spectrum of knee or hip OA [ 33 ].
Patient focus groups identifi ed two distinct types of OA pain: (1) constant aching
pain and (2) less frequent, more intense pain that is often unpredictable [ 25 ]. The
ICOAP evaluates the impact of intermittent and constant pain, with respect to inten-
sity, frequency, and effect on mood, sleep, and QOL. Unlike WOMAC and KOOS,
the ICOAP evaluates pain independent of physical function. It is intended to be used
in conjunction with a measure of physical function such as KOOS-PS or HOOS-PS.
The ICOAP was designed for administration by a clinician (in person or by tele-
phone), although it can be used in a patient-completed format. Patients respond to
each of the 11 items with respect to their pain over the previous week. There are
separate versions for knee and hip OA. It is easy for clinicians to score manually, by
summing the items for each subscale. If the patient marks outside the box, the clos-
est box is used, but if two boxes are marked, the item is considered missing. If one
or two items are missing, these are replaced with the mean score of all other items.
The patient’s response is considered invalid if three or more items are missing.
Scores are normalized to a score from 0 to 100, with higher scores indicating a
worse pain experience. Although the original publication suggested that a total
score could be calculated, subsequent statistical (Rasch) analysis indicated that, for
people with knee OA, the subscales should not be combined, and two individual
subscale scores should be calculated [ 34 ].
Developed as an OARSI/OMERACT initiative, the ICOAP has widespread
accessibility, being freely available on the OARSI website ( http://www.oarsi.org ). It has
been translated into at least 15 languages.
10 PROMs for Osteoarthritis