Physiology and Functions of Meniscus Cartilage
Meniscus is Important to Stability and Health of the Knee
The tibiofemoral joint is the primary joint of the knee and is made up of the femur and the tibia. Because this articulation has less surface to surface contact than a ball and socket type of joint (shoulder or hip), this joint has extensive connective tissue structures to enhance its stability.
Anatomy of the Knee
Because the tibiofemoral joint has less surface contact, the joint has four strong ligaments that help provide stability to the joint. These ligaments include the medial collateral ligament (medial side of the knee), the lateral collateral ligament (lateral side of the knee), and the anterior and posterior cruciate ligaments (crosses inside of the knee). Each ligament plays an important role in stabilizing the knee from outside forces.
Deep within the knee and resting on the top of the tibia (tibial plateau) are two meniscus cartilage (medial and lateral). The meniscus cartilage is a dense type of connective tissue designed to absorb and distribute the compressive load of the body from the femur to the tibia.
Functions of the Meniscus
The meniscus also plays an important role in distributing joint nutrition and lubrication within the joint. When non weight bearing, the meniscus acts like a sponge and absorbs nutrients and synovial fluid. When weight bearing, the meniscus is compressed distributing the nutrients and synovial fluid throughout the inside of the knee.
Another purpose of the meniscus is to protect the femur and tibia from direct bone to bone contact. If the meniscus has been damaged and been removed rather than repaired, the femur then rests directly on the tibia. This can damage the hyaline cartilage on the ends of the femur and/or tibia and lead to degenerative changes.
The medial and lateral meniscus are shaped slightly different, but both play a significant role in assisting the ligaments in stabilizing the knee. The structures are thicker on the outside progressively getting thinner towards the inside. This outside thickness helps the femur to stabilize on the tibial plateau. If the meniscus is torn and not repaired, stability is compromised leaving the individual at risk for further injury to the stabilizing ligaments.
The medial meniscus is more at risk for injury because the deepest layer of the medial collateral ligament is actually attached to the meniscus. If there is enough force to tear the medial collateral ligament, then the medial meniscus may be torn as well.
Meniscus Tears
There are a number of different types of tears and locations of tears that can occur to the meniscus. The location and size of the tear will determine if the individual needs surgery to repair the meniscus, surgery to remove pieces of the meniscus, or if the meniscus might be able to heal on its own.
Injuries to the outside portion of the meniscus have the best potential for healing on their own. This is because the meniscus has a better blood supply to the outside portion than the inside. A small tear to the outside of the meniscus has the potential of healing itself. However, larger tears across the length or the width of the meniscus will need to be repaired.
Indicators for surgery include:
- locking (knee feels stuck in one place)
- inability to walk without pain,
- significant joint line pain
- inability to perform daily tasks.
Repairing the meniscus is critical to the future health of the knee. A healthy and functioning meniscus is key to protecting the hyaline cartilage on the ends of the tibia and femur, providing joint nutrition, and enhancing stability.
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