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Study of Diclofenac compared to Placebo for Pain Relief in Adults with Knee Osteoarthritis

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on knee osteoarthritis, a condition that causes pain and stiffness in the knee joint. The research examines how well diclofenac, a pain-relieving medication, works compared to placebo in treating knee pain. The purpose is to evaluate how a special communication approach affects the way patients report their knee pain during treatment.

The study medication comes in the form of gastro-resistant tablets. Participants will receive either diclofenac tablets or placebo tablets that look identical but contain no active medicine. The treatment period lasts for 5 weeks, during which patients take their assigned medication daily.

Throughout the study, researchers will track changes in knee pain and physical function using various measurements. They will assess how well patients can walk and how their pain levels change from the beginning to the end of the study. The research team will also monitor how patients respond to both the active medication and placebo treatment.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

Step 1
Initial assessment
Your participation begins with a screening visit where your knee pain will be evaluated using the KOOS pain questionnaire
An x-ray of your knee will be taken to confirm knee osteoarthritis severity
Your height and weight will be measured to calculate your Body Mass Index (BMI)
Step 2
Baseline measurements
Your knee pain will be assessed again using the KOOS pain questionnaire
You will complete a 40-meter walk test to measure your walking ability
Additional pain measurements will be taken, including pressure pain threshold and pain response tests
Step 3
Treatment period
You will receive either Diclofenac 50 mg tablets or placebo tablets
The placebo tablets contain no active medicine, only inactive ingredients (lactose and starch)
The tablets should be taken by mouth
Neither you nor the study staff will know which treatment you are receiving
Step 4
Final assessment
At the end of the study, your knee pain will be evaluated again using the KOOS questionnaire
The 40-meter walk test will be repeated
Pain measurements will be taken again to compare with your initial results
Your daily function and knee-related symptoms will be assessed

Who can join the trial?

7 criteria

Must sign an Informed Consent Form (ICF) to participate in the study
Must be able to attend all study visits and follow all study rules about allowed medications
Must be between 40 and 85 years old when signing the consent form
Must have a Body Mass Index (BMI) less than 45 kg/m² (BMI is a measure of body fat based on height and weight)
Must have experienced knee pain on most days for at least 3 months before the screening visit
Must score at least 40 out of 100 on the KOOS pain questionnaire (a survey that measures knee pain) during both screening and baseline visits
Must have X-ray evidence of knee arthritis with a Kellgren-Lawrence grade of 2 or higher in at least one knee joint (this scale measures the severity of arthritis changes in the knee on X-rays)

Who cannot join the trial?

15 criteria

History of previous knee surgery or joint replacement in the affected knee
Presence of other types of arthritis (joint inflammation) besides osteoarthritis
Current participation in other clinical trials
Use of strong pain medications (opioids) in the past 3 months
Severe mental health conditions that could affect pain reporting
Pregnancy or planning to become pregnant during the study period
Severe knee injury or trauma within the past 6 months
Presence of other medical conditions that could affect knee pain assessment
History of substance abuse or dependency
Fibromyalgia (chronic condition causing widespread pain) or other chronic pain conditions
Unable to follow study instructions or complete questionnaires independently
Current infection or inflammation in the knee joint
Use of intra-articular injections (injections directly into the knee joint) within the past 3 months
Planned knee surgery during the study period
Severe obesity that significantly impacts knee function

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Verified sites

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Sanos A/S
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Gandrup, Denmark

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Investigated drugs

Diclofenac is a non-steroidal anti-inflammatory medication (NSAID) commonly used to treat pain and inflammation. It works by reducing substances in the body that cause pain and swelling. In this trial, it is being studied for its effectiveness in treating knee pain in people with osteoarthritis. This medication can be taken orally or applied directly to the skin over the painful joint.

Diclofenac Sodium

What is already known about the treatment

Diclofenac
A commonly prescribed non-steroidal anti-inflammatory drug (NSAID) that is available in various forms including tablets, topical gels, and injections, primarily used for treating osteoarthritis and other painful inflammatory conditions. It works by blocking specific enzymes (COX-1 and COX-2) that produce prostaglandins, substances in the body responsible for inflammation, pain, and fever. This medication belongs to the NSAID pharmacological class and has been well-established in medical practice for decades, with extensive clinical evidence supporting its effectiveness in managing joint pain and inflammation, particularly in conditions like knee osteoarthritis.
Placebo
A therapeutically inactive substance or treatment designed to simulate medication, typically used in clinical trials as a control to test the effectiveness of active medications. In clinical studies, placebos help researchers determine the true effect of the investigational drug by comparing outcomes between patients who receive the active medication versus those who receive the placebo, while neither the researchers nor the patients know which treatment each participant is receiving during the study period.

Investigated diseases

Knee Osteoarthritis - A degenerative joint condition that affects the knee, where the protective cartilage that cushions the ends of bones gradually wears down over time. The disease typically develops slowly and causes the joint to become painful and stiff. As the condition progresses, the smooth surface of the cartilage becomes rough and thin, and the protective space between the bones decreases. The body responds by growing new bone tissue around the joint, leading to bone spurs. Joint fluid may increase, causing swelling and reducing mobility in the knee joint.