It is known that osteoarthritis of the knee causes pain and also leads to some extent of disability. Previously, the chemical compound capsaicin has been tried as an ingredient in creams to relieve pain due to knee arthritis. High doses of this lead to burning and irritation of the skin over the knees. This study evaluated lower concentrations of this compound and found that levels as low as 0.00125 percent capsaicin, when applied over the knee in a gel, was an “effective treatment in mildly to moderately painful” osteoarthritis of the knees and caused fewer and milder side effects than higher concentrations of this chemical.
When osteoarthritis affects the knee joints, it leads to pain and also to some joint immobility and disability. As a cause of disability, it is estimated that osteoarthritis ranks fourth among females and eighth among males worldwide. Of all joint disorders, knee joint osteoarthritis causes maximum disability. Also, most medicines available for knee arthritis, including pain-killers, have severe side effects like heartburn and kidney damage. Capsaicin is a compound derived from chili peppers. Some studies have shown that it serves to control the pain in an arthritic knee when applied as a gel over the knee. Gels that have been tried are usually 0.075 to 0.05 percent in concentration and often lead to burning and irritation on the skin of the knee. This study was conducted to see if a lower concentration (0.0125 percent) of capsaicin gel could be used successfully in treating knee osteoarthritis without skin irritation and other side effects.
For this study, a total of 100 female sufferers of knee osteoarthritis, aged 44 to 82 years, with moderate pain were included.
The patients were not informed about the therapy that they received. They were given similar-looking gels to apply. Half got the capsaicin 0.0125 percent gel and the rest applied a placebo. They applied the gel three times a day for four weeks. Then after a one-week break, the treatment for the patients of the two groups was reversed without their knowledge for another four weeks.
At the end of each period, the levels of pain and disability of the patients were noted.
Results showed that pain and disability was significantly reduced when patients used the capsaicin gel compared to when they used the placebo.
Joint stiffness due to arthritis and the ability to use the joint improved with capsaicin significantly compared to the placebo.
It was seen that 67 percent of the tested patients complained of a burning feeling over the skin of the knee joint after application of the gel. However, none of the patients withdrew from the study due to intolerance of this sensation.
The authors of this study agree that it showed that users of the gel had more skin irritation compared to the placebo gel users. They add that, in spite of this side effect, none of the patients felt compelled to leave the study at any point. The authors also agree that this study found only female participants and the results may differ in men. They suggest future studies to explore the efficacy of capsaicin 0.0125 percent gel in men with knee osteoarthritis.
The study researchers concluded that applying 0.0125% concentration capsaicin-containing gel over the knee three times a day for four consecutive weeks gives more pain relief when compared to a placebo. Given the increasing number of people who suffer from knee osteoarthritis and the side effects of many pain relievers, this is welcome news. Capsaicin-containing gel has previously been found to be effective, but has never been very popular due to the side effects of local irritation of the skin. This study shows that capsaicin in a much lower concentration can also act effectively. Although this dose also causes some burning, it is better tolerated and no patient needs to discontinue therapy due to the discomfort.
For More Information:
A Low Dose of Capsaicin in Gel Helps to Control Pain in Knee Osteoarthritis Patients
Journal of the Medical Association of Thailand, 2010
By Weerachai Kosuwon, MD; Winai Sirichatiwapee, MD
From the Khon Kaen University, Khon Kaen, Thailand