Cartilage injury is the most common source of knee pain. Over two million people in the U.S. suffer cartilage problems each year. The cause may be secondary to injury, or may develop gradually without trauma. Whatever the cause, areas of damaged cartilage may cause pain and at times swelling; both of which make it difficult to maintain an active lifestyle.
Dr. Mullen offers a full range of state-of-the-art treatment options for knee cartilage injuries. These include the latest minimally invasive and arthroscopic procedures. In some cases, not only will these procedures resolve pain and restore function, they may also delay the progression of arthritis.
The knee has the difficult task of transferring the load of the body, while at the same time having the freedom to allow rapid change of direction and speed. In addition to the obvious bending motion, the knee also rotates and slides. With certain activities, the knee is subjected to almost ten times the weight of the body.
The Knee Joint
The knee joint is made up of three bones, two different types of cartilage, and four major ligaments. The three bones in the knee are:
Femur (thigh bone)
At the knee joint there are two separate prominences called condyles. The inner prominence is called the medial femoral condyle (MFC). The outer prominence is the lateral femoral condyle (LFC).
Tibia (shin bone)
The top of the tibia is called the tibial plateau. Each side is slightly cup shaped to provide an area for the femoral condyles to fit into. These are the medial and lateral tibial plateaus.
Patella (knee cap)
The patella rides in a shallow groove over the front part of the femur called the trochlea. The ends of these bones inside the joint are covered by articular cartilage.
The synovial lining of any joint is the tissue that defines the perimeter of the joint. It can be referred to as the "capsule" of a joint, surrounding all other intra-articular joint structures. The synovium is comprised of highly-innervated cells that produce oily joint fluid that keeps a joint naturally lubricated.
Articular cartilage is a firm glistening white substance. It is made up of collagen and special sponge-like molecules called proteoglycans. The articular cartilage is maintained by living cartilage cells called chondrocytes. With normal joint fluid, the surface is more slippery than water or ice. This allows the knee joint to move smoothly with very little friction.
Meniscal cartilage is the other type of cartilage in the knee. These C-shaped pads are located between the thigh bone (femoral condyles) and shin bone (tibial plateaus). There is one meniscus on each side of the knee.
The medial meniscus resides on the inner aspect and lateral meniscus on the outer side. These menisci are attached to the tibial plateaus. They serve as shock absorbers for the articular cartilage and transfer joint force. They accomplish this by distributing joint forces over a larger area of the joint, transferring force from the curved femoral condyles to the flatter tibial plateaus.
Injury to either type of cartilage can upset the normal loading of the joint. This "injury” is not limited to trauma; it may occur with normal daily activities. Once the delicate balance of the knee is upset, the resulting abnormal loads then lead to "overload damage." Over time, initially small defects in the articular cartilage, or tears in the meniscal cartilage can progress. This gradual deterioration can lead to degenerative joint disease. (Osteoarthritis)
Ligaments are rope-like structures that connect two bones. There are four main ligaments in the knee: two inner cruciate (cross) and two outer collateral (side) ligaments. Ligaments connect a bone to another bone, and are not connected to any muscle. The main function of the knee ligaments is to stabilize the knee joint and to protect the articular cartilage and menisci from injury.
If a ligament connects a bone to a bone, a tendon is a structure that connects a muscle to a bone. Tendons are mostly extra-capsular, or outside the lining of the knee. Ligaments provide what is called "static stability" to a joint because they cannot be lengthened or shortened by movement. Tendons however provide "dynamic stability" because when a patient flexes or relaxes a muscle, the tendon that connects that muscle to the bone can tighten or loosen to change the position of the bones and their relationship to each other at a joint.