In humans the knee supports nearly the entire weight of the body. The knee functions as a living, self-maintaining, biologic transmission, the purpose of which is to accept and transfer biomechanical loads between the femur; or thigh bone which is the longest, most voluminous, and strongest bone of the body and forms part of the hip and part of the knee, tibia; or shin bone, patella; or kneecap which is a thick, triangular bone that articulates with the femur and covers and protects the front of the knee joint, and fibula; or calf bone. In short, our knees are hinge joints.
Menisci are cartilaginous/rubbery tissue within the knee joint which serve to protect the ends of the bones from rubbing on each other; acts as a shock absorber between the upper and lower leg bones and stabilizes the knee joint by evenly distributing the load across the knee. There are two menisci in each knee, the medial meniscus, the inner side of the knee and the lateral meniscus, the outer side of the knee. Either or both may be cracked, or torn, when the knee is forcefully rotated and/or bent.
In a typical minor tear, there may be slight pain and swelling at first. These symptoms usually go away in 2 to 3 weeks.
A typical moderate tear can cause pain at the side or center of the knee, depending on where the tear is located. Swelling increases gradually over 2 to 3 days. This may make the knee feel stiff and limit bending, but walking is usually possible. There's often sharp pain with twisting or squatting. These symptoms go away but tend to recur with minor twisting or overuse. In severe tears, pieces of the torn meniscus can dislocate into the joint space. This can make the knee catch, pop, or lock. You may not be able to straighten it. And the knee can feel "wobbly" or unstable, or give way without warning. It may swell and become stiff right after the injury, or over 2 to 3 days.
A physical examination is done to determine if a torn meniscus is the cause of your pain and to rule out other knee injuries. Your health professional will examine both knees and evaluate tenderness, range of motion, knee stability, and how the injury has affected your knee. X-rays are usually done. Your health professional may suggest that you follow up with an orthopedic surgeon for further testing. MRI is the best imaging modality available today for diagnosing soft-tissue injuries. While X-Ray and CT are excellent tools for detecting bone injuries, they have limited value for patients with severe ligament or meniscus damage.