Table 1. American College of Rheumatology criteria for classification of hip osteoarthritis²¹.

Test Cluster 1

Pain reported in the hip

<115 degrees hip flexion range of motion (ROM)

<15 degrees hip internal rotation ROM

Test Cluster 2

Pain with hip internal rotation ROM

<60 minutes of morning stiffness

>50 years of age

Note: All three findings from either test cluster must be present in order for subject to meet clinical criteria for hip OA as defined by Altman et al.²¹