261Knee Injury and Osteoarthritis Outcome Score (KOOS) and Hip Disability
and Osteoarthritis Outcome Score (HOOS)
The KOOS ( Appendix 1 ) and HOOS were de veloped as extensions of the WOMAC
3.0 and intended for use in adults of all ages, from young adults with joint injury that
may lead to OA, to elderly patients with OA. Dimensions of function in sport/recre-
ation activities and knee/hip-related QOL were added to the WOMAC domains of
pain and function in ADL. In addition, the pain subscale was extended to incorporate
pain frequency (KOOS/HOOS), and pain when bending (KOOS/HOOS), extending
(KOOS/HOOS), twisting on knee (KOOS), and when walking on hard surfaces and
uneven surface (HOOS). The stiffness subscale was expanded to incorporate other
joint-specifi c symptoms, for example, range of motion (KOOS/HOOS), grinding/
clicking (KOOS/HOOS), catching (KOOS), and swelling (KOOS). Both the KOOS
and HOOS contain the original WOMAC 3.0 version in its entirety.
The KOOS contains 42 items, while the HOOS contains 40 items. Patients
respond to each item based on their knee/hip condition over the previous week, on
5-point Likert scales. Both are intended to be patient-completed, and paper and
electronic versions have been validated [ 29 ]. Completion time for patients is typi-
cally 10–15 min. Scoring can be performed in 2–3 min using a scoring spreadsheet
(freely available at http://www.koos.nu ). Higher scores represent better outcome. The
KOOS and HOOS are intended to be scored as fi ve individual subscales, and the use
of one aggregate score is discouraged [ 30 ]. Clinicians should be aware that only
50 % of items are required to formulate a subscale score. This means that items that
are not relevant for particular patients can be left out as required (e.g., patients who
do not have a bathtub can leave out ADL item 13, which relates to problems getting
in and out of the bath). If more than 50 % of items are missing, a subscale score
should not be calculated.
The HOOS and KOOS are freely available ( http://www.koos.nu ), and have no fees asso-
ciated with their use. The Website also provides multiple language versions of each
PROM. This enhances their accessibility for clinical use. Although associated with
longer completion times, the HOOS and KOOS provide information of fi ve dimen-
sions deemed important to patients, compared to other PROMs that evaluate fewer
dimensions or give one aggregated score for a more general outcome such as “knee
function” (where items including pain, other symptoms and diffi culty with ADL
function may be included). The latter case may make clinical interpretation more dif-
fi cult. Users should balance patient burden alongside information provided.
In contrast to WOMAC, the HOOS and KOOS have content validity for younger
adults who are more physically active. This is represented in the sport/recreation
function subscale. Importantly, the use of both functional scales (ADL and sport/
recreation) in younger patients with hip/knee problems allows clinicians to track
their function over time, from immediately post-injury to the onset and progression
of OA development. For example, the KOOS can be used to monitor patients who
have sustained ACL or meniscal injuries. However, clinicians should keep in mind
that the sport/recreation subscale may not be appropriate for older patients with
more severe hip or knee osteoarthritis who are unable or unwilling to participate in
more vigorous physical activity.
10 PROMs for Osteoarthritis