Being physically active is healthy. Strong bones and muscles improve balance and coordination and help protect joints from injury. Whether you play competitive sports or walk or run for exercise, you understand the importance of healthy joints, especially weight-bearing joints like the knees. The knee is a hinge joint that consists of numerous ligaments, tendons, cartilage, bursae, bone, synovial membrane and muscles. All of these components work together to support the body during times of strenuous physical activity as well as simply standing.