What can i do to increase my flexibility in my stiff knee?

Exercise plus more: Stiffness in the knee is a hallmark sign of arthritis, especially if it is worse after a long period of immobility (i.e. Long car ride). Moderate low impact exercises like walking generally can help. In addition, oral supplements like chondroitin and glucosamine plus injectable agents like hyaluronic acid have all shown to be effective in many people as well.