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vNonsurgical interventions, such as education, exercise therapy, diet, and pharma-
cological interventions, have small-to-moderate effects and are recommended as the
fi rst-line treatment for knee and hip OA. Those with end-stage knee or hip OA
typically undergo total joint replacement surgery.
The similarities in symptoms and functional impairments between knee and hip
OA are refl ected in the high degree of overlap between PROMs for the two condi-
tions. Some PROMs were developed with the intention to be used in either knee or
hip OA patients. Thus, we will consider PROMs for knee and hip OA together in
this chapter. These will be discussed under two headings: disease-specifi c PROMs,
which are intended for use in patients with OA, and intervention-specifi c PROMs,
which are intended for use in patients who are undergoing specifi c interventions for
OA. We have selected the most commonly used PROMs for knee and hip OA, with
a particular focus on those that have established measurement properties. Table 10.2
summarizes the characteristics of recommended PROMs for knee and hip OA,
whereas Table 10.1 provides a quick-reference guide regarding the evidence for
whether the PROMs satisfy the requirements of a “good” PROM for knee and hip
OA. All PROMs described in this section were developed with input from patients
with knee and/or hip OA, ensuring their content validity.
Patient-Reported Outcome Measures Specifi c for Hip and/or
Knee Osteoarthritis
Western Ontario and McMaster Universities Osteoarthritis Index
(WOMAC)
The WOMAC was developed for patients with knee or hip OA [ 16 ]. It comprises 24
items assessing pain, stiffness, and function in activities of daily living (ADL).
Patients respond to each item based on the previous 48 hours, which reduces recall
bias. WOMAC is available in a variety of formats (Likert scale and VAS) and has
been validated in paper, electronic (e.g., computer and smartphone), and telephone
versions [ 17 – 20 ]. This enhances its clinical use, especially for patients with com-
munication diffi culties. It takes less than 12 min for patients to complete, and 5 min
for clinicians to calculate the three subscale scores (manual/computer). For missing
items, the mean value of all answered items within the subscale should be entered
[ 21 ]. Subscale scores should not be calculated if two or more pain items, both stiff-
ness items, or four or more physical function items are missing [ 22 , 23 ]. Higher
scores represent worse outcome.
There are considerations regarding the content of WOMAC. There is a high
degree of overlap between the pain and ADL subscales [ 24 ]. This is likely due to the
nature of the pain questions, which ask about the severity of pain during particular
functional activities for which the corresponding diffi culty is the focus of the ADL
subscale (e.g., pain during walking). This suggests that the pain subscale should be
N.J. Collins and E.M. Roos