Pain and Body Function Limitations in Primary Knee Osteoarthritis: A Cross-sectional study on International Classification of Functioning, Disability and Health based Assessment

Background

The impact of knee Osteoarthritis (OA) on Quality of life (QoL) is profound. Individuals with knee OA often experience chronic joint pain, morning stiffness, and progressive difficulty in performing basic tasks such as walking, climbing stairs, and squatting. These limitations not only hinder physical mobility but also affect emotional well-being, social participation, and independence. Studies have shown that the severity of knee pain and functional disability are directly associated with lower scores on health-related QoL assessments, such as the Short Form-36.

The association between pain and function in knee OA is well-documented, integrating this relationship using the ICF framework offers a more holistic understanding. This approach may help bridge gaps in clinical assessment and promote individualized care strategies tailored to the specific functional challenges experienced by OA patients.

By using the ICF framework, the study will likely reveal how pain intensity affects not just mobility but also broader aspects of daily living and participation. It is anticipated that individuals reporting higher Numeric Pain Rating Scale (NPRS) scores will also show more limitations in ICF activity domains such as walking, stair-climbing, self-care, and social participation. The study will also provide ICF-based functional profiles that can help classify patients based on pain-disability patterns.

Primary Objective

To assess the relationship between pain intensity and body function limitations in individuals with knee osteoarthritis using the International Classification of Functioning, Disability and Health (ICF) framework.

Secondary Objective

To examine the association between radiographic severity (Kellgren-Lawrence grade), Pain and functional limitations (WOMAC).

Methodology

Type of study Cross-sectional Study

Duration of Study Two years

Study Population Patients of Primary Osteoarthritis Knee

Total Sample Size= Two hundred thirty nine

Inclusion Criteria

Age  more than fifty years

Symptoms of primary osteoarthritis knee with radiological evidence of OA knee

 Exclusion Criteria

Post-traumatic or post-operative knees

Neurological or rheumatologic comorbidities

Neuromuscular Disorders

Cognitive impairment

Refusal of consent to take part in study

Sampling Technique

Consecutive sampling will be employed to select study participants from patients attending the Outpatient Department (OPD) or In-patient Department (IPD) of Physical Medicine and Rehabilitation.

Study Plan

Patient will be recruited from department of Physical Medicine and Rehabilitation OPD/IPD. Study will be started only after getting approval from Institutional Ethical Committee. Patients will be evaluated for inclusion and exclusion criteria. Written and informed consent will be taken from all participants. All the data will be recorded in working proforma Patients will be evaluated using 3 Scales/questionnaires: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for functional assessment. Pain will be assessed using Numeric Pain Rating Scale (NPRS). Body Functions in ICF Core Set for Osteoarthritis (Comprehensive) for assessment of body functions.

Scales/Questionnaires

Numerical Pain rating Scale (NPRS): It is a commonly used, simple, and effective tool for assessing the intensity of pain experienced by an individual. Patients are asked to rate their pain intensity by selecting a number between 0 (no pain) and 10 that best describes their current pain experience. The scale is typically presented visually (on a line or as a series of numbers) or verbally, depending on the clinical context. The scale is valid, reliable and has internal consistency of 0.87.

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Scale: It is a widely validated, disease-specific instrument used to evaluate pain, stiffness, and functional limitation in individuals with knee and hip osteoarthritis (OA). It comprises 24 items divided into three subscales- pain (5 items), stiffness (2 items), and physical function (17 items). The WOMAC can be administered using Likert, Visual Analog Scale (VAS), or Numerical Rating Scale (NRS) formats, with higher scores indicating worse symptoms. WOMAC has demonstrated excellent psychometric properties in knee OA populations. The internal consistency is high, with Cronbach’s alpha ranging from 0.86 to 0.96 for its subscales, and test-retest reliability coefficients exceeding 0.80, confirming its stability over time. It has strong construct and content validity, with responsiveness to clinical changes, making it a preferred outcome measure in OA research and rehabilitation settings.

Body Functions in ICF Core Set for Osteoarthritis (Comprehensive): It is a standardized tool based on the WHO’s International Classification of Functioning, Disability and Health (ICF) framework. It includes key categories across body functions, activities, participation, and environmental factors relevant to individuals with osteoarthritis. This tool enables a comprehensive assessment of how OA affects daily life and social functioning. It has demonstrated strong content and construct validity, and studies show moderate to high inter-rater reliability when used by trained professionals. The brief format makes it suitable for clinical and research settings, supporting a holistic, patient-centered approach to OA assessment. It covers three major domains: Body Functions, Activities and Participation, and Environmental Factors. Body Function has 13 body function assessment, scores from 0 to 4, not specified and not applicable.

Statistical Analysis

Descriptive statistics will be used to summarize demographic variables and responses from the ICF Core Set for Osteoarthritis (Brief), including measures such as frequency, percentage, mean, and standard deviation as appropriate. To examine associations between categorical variables, the Chi-square test will be applied. ICF responses with not specified and not applicable will be not included in ICF based stats analysis. Correlation between pain intensity and body function limitations, will be analyzed using correlation analysis, either Pearson’s or Spearman’s correlation coefficient, depending on the distribution of the data. To identify whether pain levels can predict the degree of body function limitation, a regression analysis will be performed. For all statistical tests, a p-value of less than 0.05 will be considered statistically significant. All data will be analyzed using IBM SPSS Statistics software, version 29.