The knee is an incredible joint. It can straighten and bend while supporting your body weight—or more if you're lifting weight—and handle the stress of athletic movements such as sprinting and jumping.
And it can do all of this smoothly and without pain thanks to the meniscus.
We talked to Dr. Christopher Kaeding, an orthopaedic surgeon specializing in sports medicine at The Ohio State University Wexner Medical Center, to learn more about the anatomy of the meniscus, injuries and treatment.
What is the Meniscus?
The meniscus is a C-shaped fibrocartilaginous pad—cartilage for short—found in each knee. Attached to the top of the tibia, it forms two small padded cups on the bottom of the knee so the tibia can smoothly hinge with the femur.
The meniscus helps absorb impact forces when you walk, run and land from a jump by more evenly distributing these forces across the knee.
"The two surfaces [of the bones] are running into each other and [the meniscus] makes them match up," says Kaeding. "When they match up better, there's a decrease in the peak contact force, so it helps spread out the load over a larger area in the knee joint."
The result is pain-free knee function through a full range of motion.
Without the meniscus, it would more difficult to move your knees, and the joints could lock in certain positions. Also, the femur and tibia would gradually grind against each other, causing significant pain.
What is a Meniscus Injury?
Most acute or sudden meniscus injuries occur when the knee is under load, bent and/or making some type of twisting motion such as when planting and cutting in sports like football, soccer, basketball and tennis. The meniscus is often torn along with ACL and MCL —an injury referred to as the "Unhappy Triad."
However, you don't need to be playing a high-speed or contact sport to experience a meniscus injury. The wrong movement in a poor position when performing simple tasks can result in an injury.
"You can tear a meniscus working in the garden or cleaning out the garage," says Kaeding. "It doesn't require a high-energy football collision to tear a meniscus."
The meniscus can also gradually degrade over time. Kaeding equates this type of injury to bending a paperclip over and over again. It will weaken and eventually break.
When the meniscus is torn, it leaves an unstable fragment in the knee. Symptoms include pain, swelling and impaired range of motion. Telltale signs of a meniscus injury are the knee getting stuck in certain positions and pain when standing up out of a seated position or walking up stairs. The amount of pain depends on the severity and location of the injury. You may experience minor discomfort and pain during certain knee movements, or significant knee pain that needs to be dealt with before you can resume normal activity.
"The symptoms can be from painful locking and something shifting in your knee and you can't fully straighten or bend it, or it could be sharp pain or achiness or soreness," says Kaeding.
It's not uncommon for athletes to play through a meniscus tear and address it at the end of the season if the injury isn't serious. However, some cases require surgery before an athlete can get back on the field.
Long-term, a meniscus injury that's not addressed can cause premature degeneration of the knee joint, because the cartilage no longer fully protects the surfaces of the femur and tibia.
"Having an unstable fragment in your knee can lead to damage of the white articular cartilage on the surface of the bone, and you can start having concerns about arthritis in the knee," Kaeding says.
Meniscus Injury Treatment
Treating a meniscus injury is tricky because there's little or no blood supply to the cartilage, which Kaeding says is similar to a fingernail. And it only gets worse with age. If it's a minor injury, rest and physical therapy usually do the trick. However, a significant tear will require surgery.
Common surgical repair involves stitching the damaged meniscus if the tear is near a blood supply. Most of the time, the damaged portion of the meniscus is trimmed off in a procedure called a meniscectomy. People often refer to this as "getting their knee cleaned up."
If there's significant damage or multiple tears, the meniscus is replaced with a meniscus from a cadaver. According to Kaeding, meniscal replacements have decent success rates; however, they're only performed on younger individuals.
For those in their 40s or older, Kaeding and his team are pioneering a plastic implant designed to replicate the function of the meniscus.
"We put this device in and hopefully we restore meniscal function, decrease contact forces, spread out the load of the knee and hope to give you less pain and decrease the progression of arthritis," he says.
Although promising, this device is still undergoing FDA trials. Hopefully it will prove successful, and help to revolutionize how we treat meniscal injuries.
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