The meniscus is a C-shaped piece of tough, rubbery cartilage that sits between your thighbone and shinbone, acting as a cushion and shock absorber in your knee joint. You actually have two in each knee: one on the inner side (the medial meniscus) and one on the outer side (the lateral meniscus). Together, they carry a remarkable amount of your body weight, stabilize the joint, and protect the smooth cartilage coating your bones from wearing down. Understanding what the meniscus does helps explain why injuries to it are so common and why they matter for long-term knee health.
Shape, Size, and Position
The two menisci look similar at a glance, but they differ in meaningful ways. The medial meniscus on the inner side of the knee is generally described as C-shaped, while the lateral meniscus on the outer side is more O-shaped, forming a tighter circle. Despite these shape differences, their volumes are nearly identical, each roughly 2.4 milliliters of tissue. The medial meniscus is slightly thicker, with a maximum thickness around 7.7 mm compared to 7.2 mm for the lateral.
Where they sit on the shinbone (the tibial plateau) also differs. The lateral meniscus covers about 59% of the outer tibial surface, while the medial meniscus covers only about 50% of the inner surface. That means more bare bone is exposed on the inner side of your knee, which partly explains why medial meniscus injuries tend to cause more problems over time.
What the Meniscus Actually Does
The meniscus is not just padding. It distributes weight across the knee joint so that force doesn’t concentrate on a single point of bone. The medial meniscus bears roughly 50% of the load on the inner compartment of the knee, and the lateral meniscus handles about 70% of the load on the outer side. Without this load-spreading function, the smooth cartilage on the ends of your bones would break down much faster.
Beyond load distribution, the menisci help stabilize the knee during twisting and pivoting movements. They also assist with joint lubrication by helping spread synovial fluid, the natural lubricant inside the joint, across the cartilage surfaces. When part of the meniscus is damaged or removed, all of these functions are compromised to some degree.
Blood Supply and Healing Zones
One of the most important things about the meniscus is that it has very limited blood supply, and this directly affects whether a tear can heal. Doctors divide the meniscus into three zones based on blood flow. The outer edge, closest to the joint capsule, has good blood supply and is called the “red-red zone.” The middle section, where blood supply starts to thin out, is the “red-white zone.” The inner portion, closest to the center of the knee, has almost no blood supply at all and is called the “white-white zone.”
Tears in the red-red zone have the best chance of healing, either on their own or with surgical repair, because blood delivers the oxygen and nutrients tissue needs to mend itself. Tears in the white-white zone heal poorly, which is why many inner tears end up being trimmed rather than repaired.
How Meniscus Tears Happen
Meniscus tears fall into several categories depending on their shape and direction. Longitudinal tears run along the length of the meniscus, parallel to its outer edge. When a longitudinal tear extends far enough, the torn flap can fold into the center of the joint like the handle of a bucket, earning it the name “bucket-handle tear.” These are often traumatic and frequently occur alongside anterior cruciate ligament (ACL) injuries.
Radial tears cut from the inner edge outward toward the periphery. These are graded by how far they extend: a tear reaching less than 50% of the meniscus width is mild, while a complete radial tear extends all the way to the outer rim and disrupts the meniscus’s ability to distribute load. Flap tears involve a combination of a radial tear with a loose piece of tissue that can catch in the joint during movement.
In younger people, meniscus tears typically result from a specific injury, often a hard twist or pivot during sports. In people over 40, tears are more commonly degenerative, developing gradually as the tissue weakens with age and use.
Symptoms of a Torn Meniscus
The hallmark symptoms of a meniscus tear are pain along the joint line (the seam where your thighbone meets your shinbone), swelling that develops over several hours, and a restricted range of motion. Many people describe a catching or clicking sensation when bending and straightening the knee. In more severe tears, particularly bucket-handle tears, the knee can lock in a bent position because the displaced tissue physically blocks full extension.
Some people also feel like their knee might give way beneath them, especially during twisting movements or when walking on uneven ground. With degenerative tears, symptoms can be more subtle: a nagging ache that worsens with squatting, kneeling, or climbing stairs, sometimes without any obvious triggering injury.
How Meniscus Tears Are Diagnosed
Doctors use a combination of physical examination and imaging to diagnose meniscus tears. During the exam, several hands-on tests help provoke symptoms. The McMurray test involves rotating and extending the knee while feeling for a click at the joint line. The Apley test compresses and then distracts the joint while the knee is bent, checking whether compression causes more pain than distraction (which points to the meniscus rather than ligaments). Additional tests like the Childress “duck waddle” test load the back portion of the meniscus by having you walk in a deep squat.
No single physical test is definitive. Individual tests have accuracy rates between about 48% and 63%. When doctors combine several tests together, sensitivity improves to around 89%, meaning the tests are good at detecting tears when they exist, but specificity remains low (around 30-42%), meaning they sometimes suggest a tear that isn’t there. For this reason, MRI is typically used to confirm the diagnosis and pinpoint the tear’s location and type.
Treatment: Repair vs. Removal
Treatment depends on where the tear is, how large it is, and how symptomatic it is. Small, stable tears in the outer (red-red) zone may heal with rest, physical therapy, and activity modification alone. When surgery is needed, there are two main approaches: meniscus repair, which stitches the torn tissue back together, and meniscectomy, which trims away the damaged portion.
Repair preserves the meniscus and produces better long-term outcomes. Patients who undergo meniscus repair score significantly higher on nearly all measures of knee function compared to those who have a meniscectomy. The trade-off is a longer recovery and a higher reoperation rate: about 20.7% of repairs require a second procedure, compared to 3.9% of meniscectomies. But the long-term picture favors repair. At 10 years, about 17% of meniscectomy patients develop secondary osteoarthritis compared to 10% of repair patients, and the associated need for knee replacements makes meniscectomy more expensive over a decade ($31,528 vs. $22,590).
Recovery Timelines
After a meniscectomy (trimming), recovery is relatively quick. Most people can drive within one to three days and return to normal activities within a few weeks. Physical therapy focuses on regaining strength and range of motion, and many people feel close to normal within four to six weeks.
Meniscus repair requires more patience. You’ll typically use crutches for two to four weeks and wear a knee brace for about six weeks. Physical therapy starts immediately but progresses more gradually to protect the healing tissue. Most people are out of the brace by six to eight weeks, and full recovery takes six to nine months depending on activity level. Driving is usually possible two to three weeks after surgery on the right knee, or one to two weeks after left knee surgery.
Why the Meniscus Matters Long-Term
The link between meniscus damage and osteoarthritis is strong and well documented. When the meniscus can no longer distribute load properly, the cartilage on the bone surfaces takes more direct impact with every step, accelerating wear. In one study, 100% of knees with osteoarthritis had at least one meniscus problem, and medial meniscus tears were found in over 70% of osteoarthritic knees compared to just 3% of knees without arthritis. Higher body weight compounds the issue, as increased loading on a compromised meniscus speeds up cartilage destruction.
The relationship goes both ways. Osteoarthritis can cause the meniscus to degenerate, and meniscal degeneration can accelerate arthritis. This cycle is one reason preserving as much meniscus tissue as possible during treatment is considered so important. Even in people over 50 without any arthritis symptoms, roughly a third already have some form of meniscus pathology on imaging, a reminder that not every meniscus change requires intervention, but that the tissue plays a central role in keeping your knee healthy for decades.