A study, published in the August journal of Phytotherapy Research, said Pycnogenol -- bark extract from the French maritime pine tree -- reduced overall knee osteoarthritis symptoms by 20.9 percent and lowered pain by 40.3 percent.

Researchers in Comenius University School of Medicine in Bratislava said 100 patients with stage I or II osteoarthritis were included in the study and were randomly allocated to either a Pycnogenol or a placebo. Patients were supplemented with 150 mg Pycnogenol or placebo per day for three months. They were allowed to continue taking pain medication prescribed before the study but had to record every pill taken.

The Western Ontario McMaster questionnaire for joint function was employed to rate the pain level, and obtain measures of joint stiffness and to what extent the arthritis affects participation in daily activities.