Overview
People with knee osteoarthritis may have similar levels of pain but very different abilities to walk, rise from a chair, and perform daily activities. This study aims to examine the factors associated with these differences in functional capacity among patients with similar knee pain severity.
Adults with radiographic knee osteoarthritis and an average knee pain level of 4-6 on a 0-10 scale will be included. During a single study visit, participants will complete questionnaires about physical function, central sensitization-related symptoms, and physical activity. They will also perform a 10-meter walk test, a 30-second chair stand test, and the Timed Up and Go test.
Self-reported physical function will be assessed using the function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index. Participants with better and poorer function will be compared, and the clinical factors independently associated with functional capacity will be examined. No treatment or intervention will be assigned as part of this study.
Description
Pain severity does not fully explain functional limitation in knee osteoarthritis. Patients with similar levels of knee pain may differ substantially in their ability to perform daily activities and physical tasks. This study will examine functional capacity within a group of patients whose pain severity is restricted to a similar moderate range.
In this study, "functional reserve" refers to the relative preservation of function among patients with comparable pain intensity. It is a study-specific operational concept rather than a separate validated measurement scale. Functional capacity will be evaluated using the function subscale of the Western Ontario and McMaster Universities Osteoarthritis Index. Higher scores indicate greater functional limitation.
The primary analysis will use the function score as a continuous variable in the full study sample. Multivariable linear regression will be used to examine whether demographic and clinical characteristics, radiographic disease severity, central sensitization-related symptom burden, and physical activity are independently associated with functional capacity.
An additional group-based analysis will compare participants in the lowest 25% and highest 25% of the function score distribution. The lowest quartile, representing less functional limitation, will be defined as the higher functional reserve group. The highest quartile, representing greater functional limitation, will be defined as the lower functional reserve group. These groups will be compared in terms of objective physical performance and relevant clinical characteristics. This approach will be used to explore why patients with similar pain severity may have markedly different levels of function.
Eligibility
Inclusion Criteria:
- Age 40-75 years
- Clinical and radiographic diagnosis of knee osteoarthritis
- Kellgren-Lawrence grade 2 or 3 knee osteoarthritis
- Knee pain lasting at least 3 months
- Average knee pain intensity during the previous week between 4 and 6 on a 0-10 visual analog scale
- Ability to provide written informed consent
Exclusion Criteria:
- Kellgren-Lawrence grade 1 or 4 knee osteoarthritis
- Inflammatory rheumatic disease
- History of knee surgery or intra-articular knee injection within the previous 6 months
- Neurological disease that substantially affects knee function
- Severe cardiopulmonary disease that prevents walking or performance testing
- Cognitive impairment that prevents participation in the assessment procedures
- For participants with bilateral knee osteoarthritis, assessments will be performed on the more painful knee.
