There's no good evidence for it. The hype is based on laboratory studies that suggest shark cartilage contains some health-promoting ingredients. But there's a great distance between chemical analysis in the test tube and real effects in human bodies. No one has shown that shark cartilage actually works in the treatment of diseases. And there's little regulation of the quality, source, or content of shark cartilage products on the market.
Research suggests that glucosamine can help osteoarthritis.
After three years, those who took glucosamine sulfate daily had significantly less pain, restriction of movement, and lost joint space than those who took placebos. But glucosamine is normally given to osteoarthritis patients in glucosamine sulfate capsules. In this form, glucosamine is easily absorbed by the body. By contrast, the molecules in shark cartilage are extremely large and difficult for the body to absorb. The subjects were monitored for 12 weeks.