Pain on the outer side of the knee is usually related to meniscal tears, injuries to the collateral ligaments,
and even to arthritis. Ligament injury
causes pain to worsen on walking, bending
and stretching the knee. Meniscii too if torn or injured, result in joint instability—that is you are not confident the knee joint will take your weight. Often the person feels a popping sensation on moving the joint. Pain worsens on walking.