262
Because the KOOS/HOOS pain and function in ADL subscales are comprised
largely of the corresponding WOMAC subscales, clinicians should be aware that
overlap between the two subscales is still a consideration. Although the KOOS and
HOOS have an additional item relating to frequency of knee/hip pain, the pain sub-
scale is still predominantly related to pain during ADL.
For all KOOS and HOOS subscales in knee and hip OA, respectively, there is
confl icting evidence regarding test–retest reliability. Although all subscales are suf-
fi ciently reliable for use in groups, fi ndings are mixed for use in individual patients.
Clinicians can account for this when interpreting an individual patient’s KOOS
scores by ensuring that changes exceed the MDC. For an individual patient with
knee OA, the change in pain score should exceed 26.4, symptoms 21.2, ADL 23.8,
sport/recreation 49.1, and QOL 24.9, to be considered a real change in condition
[ 31 ]. For an individual patient with hip OA, clinicians can use values for the small-
est detectable difference (SDD) to decide whether changes in subscale scores repre-
sent real change in condition. This is 15.1 for pain, 10.5 for symptoms, 9.6 for ADL,
15.5 for sport/recreation, and 16.2 for QOL [ 32 ]. Clinicians should note that differ-
ences in methods used to calculate the MDC and SDD mean that these values should
not be compared.
The HOOS is responsive to improvements with pharmacological interventions
and total hip replacement in patients with hip OA, whereas the KOOS can detect
improvements with physical therapy and total knee replacement in patients with
knee OA. The responsiveness of the HOOS following physical therapy has not been
evaluated in a psychometric study. A large number of clinical trial reports, however,
fi nd signifi cant improvements from a multitude of treatments when evaluated by the
KOOS or HOOS. Floor effects associated with the sport/recreation subscales of the
HOOS and KOOS in patients with more severe OA mean that this subscale may not
be able to detect deterioration. However, it is also likely that this subscale is not
relevant for this whole patient population. Ceiling effects have not been detected in
patients with OA, but are possible after total joint replacement (Table 10.1 ).
KOOS Physical Function Short Form (KOOS-PS) and HOOS Physical
Function Short Form (HOOS-PS)
An Osteoarthritis Research Society International (OARSI)/OMERACT initiative,
the KOOS-PS and HOOS-PS were developed as measures of physical function for
people with knee and hip OA, respectively. Statistical analysis (Rasch analysis) was
used to select items from the ADL and sport/recreation subscales of the KOOS and
HOOS in order to provide a shorter, single measure of physical function. This was
aimed at reducing item redundancy detected in the WOMAC and HOOS function
subscales. Clinicians should be aware that the KOOS-PS and HOOS-PS do not
evaluate pain, symptoms, or hip/knee-related quality of life.
The KOOS-PS contains seven items, whereas the HOOS-PS contains fi ve items,
relating to function over the previous week. They are intended to be patient- completed,
taking approximately 2 min. Scoring can be performed in less than 5 min, with higher
N.J. Collins and E.M. Roos