Hip disability and Osteoarthritis Outcome Score

Abstract

The Hip disability and Osteoarthritis Outcome Score (HOOS) is a widely utilized patient-reported outcome measure (PROM) specifically developed for the comprehensive evaluation of symptoms and functional limitations in individuals experiencing hip-related complaints, particularly those diagnosed with Osteoarthritis. This self-administered questionnaire consists of 40 items categorized across five distinct subscales: Symptoms (5 items), Pain (10 items), Activities of Daily Living (ADL) (17 items), Sport and Recreation Function (4 items), and Hip-related Quality of Life (4 items). The scoring mechanism employs a 5-point Likert scale (ranging from 0 to 4), where raw scores are converted to a 0–100 standardized score. A higher resulting score consistently reflects superior functional status and fewer reported problems or disabilities.

Keywords

HOOS, Hip disability, Osteoarthritis, Patient-Reported Outcome Measure (PROM), Functional limitations, Hip pain, Quality of life, Lower extremity, ADL.

Authors

Klässbo M (2003), de Groot IB, et al. (2007) (for the Dutch adaptation).

Purpose

The primary purpose of the HOOS is to provide a standardized, sensitive, and reliable instrument for assessing the impact of hip symptoms and disease progression, predominantly in the context of Osteoarthritis. It is designed to capture the patient’s subjective experience across multiple dimensions of function and well-being.

The scale is particularly valuable in clinical settings for monitoring patient progress over time, evaluating the effectiveness of conservative treatments (like physical therapy), and assessing outcomes following major surgical interventions, such as total hip replacement. By offering scores for five separate domains rather than a single global score, the HOOS enables clinicians and researchers to identify specific areas of functional impairment or improvement with precision.

Construct

The HOOS measures the complex, multidimensional construct of hip-related disability and functional status. It integrates physical limitations, pain perception, and the resulting impact on lifestyle and emotional health. The scale is rooted in the recognition that hip dysfunction affects various levels of activity, from basic self-care to high-demand sports.

The five measured domains represent the core components of the construct:

• Symptoms: Items focusing on mechanical symptoms such as joint stiffness, swelling, and grinding/clicking.
• Pain: Items assessing the severity and frequency of pain experienced during various routine and specific activities (e.g., twisting, sitting, weight-bearing).
• Activities of Daily Living (ADL): The largest subscale, evaluating difficulty performing essential, everyday tasks like walking, standing, rising from a seated position, and using stairs.
• Sport and Recreation Function: Items designed to assess the patient’s ability to engage in strenuous activities, running, jumping, and recreational exercises.
• Hip-related Quality of Life (QOL): Items addressing the psychological and social consequences of the hip condition, including frustration, loss of confidence, and limitations in lifestyle.

Validity

The HOOS demonstrates strong evidence of content and criterion validity. Content validity is established by ensuring that the items comprehensively cover the range of symptoms and functional limitations relevant to patients with hip pathology. The items were derived from patient interviews and refined through expert orthopedic consensus, ensuring clinical relevance.

Criterion validity has been confirmed through high correlations between HOOS subscales and scores from comparable legacy instruments, most notably the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Furthermore, the scale exhibits excellent construct validity, showing expected correlations with measures of general health (e.g., SF-36) and demonstrating the ability to differentiate between patient groups with varying degrees of hip disease severity.

Reliability

The HOOS possesses highly favorable reliability characteristics, crucial for its application in both research and clinical practice. Studies consistently report high internal consistency, typically measured by Cronbach’s alpha coefficients exceeding 0.80 for all five subscales. This indicates that the items within each domain are highly interrelated and measure the same underlying trait.

Additionally, test-retest reliability is strong, confirming the stability of the scores over short periods in patients whose clinical condition has not changed. This high reliability ensures that any significant score variation observed over time is likely attributable to genuine clinical change following treatment, rather than measurement error.

Factor Analysis

Factor analytical studies, including both exploratory and confirmatory techniques, generally support the intended five-factor structure of the HOOS. These analyses confirm that the 40 items cluster appropriately into the predetermined domains (Symptoms, Pain, ADL, Sport/Recreation, and QOL). While the five factors are distinct, they exhibit moderate to high inter-correlations, acknowledging the holistic nature of hip disability.

The validated factor structure underscores the importance of interpreting the HOOS as a multidimensional profile rather than a single, summative measure. This structure allows the scale to maintain high sensitivity to changes in specific functional areas, which is critical for outcome assessment following targeted interventions.

Instrument

Test Type: Psychometrics Scale / Patient-Reported Outcome Measure (PROM)

Format: Self-administered Questionnaire (40 items assessed via a 5-point Likert scale).

Language Available: Swedish (Original), Dutch, English, and numerous other officially validated translations globally.

Population Group: Patients suffering from hip pain or disability, particularly those diagnosed with Osteoarthritis or those pre- and post-operative for hip surgery.

Age Group: Adults and Elderly.

Population Details: Primarily used in orthopedic and physical therapy settings for individuals dealing with lower extremity functional impairment stemming from bone, joint, or cartilage disorders (Musculoskeletal system).

Test Methodology: Patients rate their perceived difficulty or frequency of symptoms over the past week using a 5-point Likert scale (0 to 4). Scores are then standardized to a 0–100 scale, where 100 represents the absence of symptoms and maximum function, and 0 represents extreme symptoms and disability.

Keywords

PROM, Musculoskeletal assessment, Functional outcome, Lower extremity disability, Hip replacement, Joint function, Psychometrics, Orthopedic assessment.

Authors

Author ORCID Identifier: N/A

Affiliation Email addresses: N/A

Correspondence Address: N/A (Refer to original publications by Klässbo M, 2003, and the official HOOS website for current licensing contact information)

Permissions & Fee and Test Year

The HOOS was originally developed and published in 2003 by Klässbo M. The Dutch adaptation, referenced in the source content, was validated in 2007 (de Groot et al.). The scale is widely available for clinical and non-commercial academic research use, often without charge, though specific licensing agreements may be required for commercial applications or large-scale systematic reviews. Users must consult the official licensing body or the original author group to confirm current permissions and any associated fees.

Reference’s

• Klässbo, M., Larsson, E., & Mannevik, E. (2003). Hip disability and Osteoarthritis Outcome Score (HOOS) validation of a Swedish version. BMC Musculoskeletal Disorders, 4(1), 16.
• de Groot, I. B., Reimus, T., & Favejee, M. M. (2007). The Dutch version of the Hip disability and Osteoarthritis Outcome Score (HOOS): Validation and reliability. Physical Therapy in Sport, 8(2), 78-83.
• The explanatory form for the instrument can be downloaded here: HOOS-form.pdf
• The original measurement instrument can be downloaded here: HOOS-meetinstr.pdf

Items of the Hip disability and Osteoarthritis Outcome Score

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way. The HOOS consists of 40 items divided into five domains:

• Symptomen (5 items)
• Pijn (10 items)
• ADL (17 items)
• Sport/Vrije tijd (4 items)
• Kwaliteit van leven (4 items)