Home-Based Quadriceps Isometric Exercise for Knee Osteoarthritis Pain

This study is a prospective randomized 4×2 factorial pilot trial conducted in community-dwelling older adults with symptomatic knee osteoarthritis. The purpose is to evaluate the feasibility, safety, and preliminary effectiveness of a brief home-based quadriceps isometric exercise program for short-term pain reduction, and to explore whether topical cannabidiol (CBD), arnica, or their combination modify the exercise response.

Participants are randomly assigned to one of four topical treatment groups (placebo, CBD, arnica, or CBD + arnica) and stratified to either an exercise or no-exercise condition, resulting in eight factorial subgroups. Randomization is computer-generated with allocation concealment using sequentially numbered opaque sealed envelopes.

The intervention period lasts 28 days. Participants allocated to the exercise condition perform daily quadriceps isometric contractions at home consisting of three sets of 10-second near-maximal voluntary contractions with rest intervals, requiring approximately 6 minutes per day. Topical formulations are applied twice daily to the affected knee. Adherence is monitored using daily logs.

The primary outcome is change in knee pain intensity measured using a Visual Analog Scale (VAS) at day 28. Secondary outcomes include feasibility indicators (adherence and retention), safety (adverse events), and exploratory changes in anthropometric and body composition measures.

Analyses are exploratory and include factorial ANCOVA adjusted for baseline values to estimate main effects of exercise and topical treatment, as well as interaction effects. Effect sizes are calculated to aid clinical interpretation.

As a pilot study, results are intended to inform the design and sample size estimation of future adequately powered randomized controlled trials evaluating low-cost, home-based rehabilitation strategies for older adults with knee osteoarthritis.

Inclusion criteria

• Adults aged 65 years or older

Clinical diagnosis of chronic knee osteoarthritis according to American College of Rheumatology criteria

Knee pain for ≥3 months

Baseline knee pain intensity ≥4 on a 10-cm Visual Analog Scale (VAS)

Ability to walk independently with or without assistive devices

Ability to understand study procedures and provide written informed consent

Exclusion criteria

• Recent knee surgery or intra-articular injection within the last 3 months

Planned knee surgery during the study period

Severe neurological or cardiovascular conditions limiting exercise participation

Skin lesions or hypersensitivity to topical formulations

Current use of topical analgesics on the target knee

Cognitive impairment preventing adherence to the protocol

Participation in another clinical trial within the last 30 days