HOOS (Hip disability and Osteoarthritis Outcome Score)

The Hip Disability and Osteoarthritis Outcome Score was developed to capture the full spectrum of hip-related impairment in patients with or without confirmed osteoarthritis. Its 40 items are organized into five subscales: Pain (10 items), Symptoms including stiffness (5 items), Activities of Daily Living (17 items), Sport and Recreation (4 items), and Hip-Related Quality of Life (4 items). Each item uses a five-point Likert response ranging from no problem to extreme problem; raw subscale scores are normalized so that 100 represents no symptoms and 0 represents the worst possible state. The instrument embeds the full WOMAC Osteoarthritis Index, allowing WOMAC scores to be extracted from the same administration. Test-retest reproducibility is high (ICC >0.78), and administration takes roughly 10–15 minutes.

Shorter variants exist for settings where respondent burden is a concern. The HOOS, JR (Joint Replacement) compresses the instrument to 6 items and is the version specifically endorsed by the American Academy of Orthopaedic Surgeons and the American Academy of Hip and Knee Surgeons for post-total-hip-arthroplasty (THA) monitoring, including for Centers for Medicare & Medicaid Services (CMS) value-based reporting. The HOOS-12 offers an intermediate 12-item format that yields three domain-specific scores and a summary score, validated in moderate-to-severe OA patients undergoing total hip replacement. LOINC code 72092-0 identifies the full HOOS panel in structured data environments.

The instrument is best interpreted alongside complementary measures. Professional guidelines recommend pairing HOOS with tools such as the modified Harris Hip Score or the Numeric Pain Rating Scale when a fuller clinical picture is needed. Minimum clinically important difference (MCID) values for HOOS, JR range from roughly 7–10 points by distribution-based methods and up to 18 points by anchor-based methods at one- to two-year follow-up, and these thresholds shift across time points within the same cohort—a nuance that matters when auditing post-operative improvement benchmarks.

CMS quality-reporting programs and value-based care contracts require documented patient-reported outcome measures (PROMs) around joint replacement episodes. Submitting HOOS, JR scores at the appropriate pre- and post-operative intervals satisfies that requirement; failure to capture or link scores to the correct encounter can trigger compliance gaps, prevent quality bonus payments under MIPS/MACRA, or cause claim-level denials when payers audit for bundled-payment episode documentation. Selecting the wrong HOOS variant—for instance, applying the full 40-item HOOS where HOOS, JR is contractually specified—can invalidate the score for regulatory purposes even if the data were collected.