You’re chasing your kids around the yard when suddenly you feel a “pop” in your knee. Or you’re playing basketball and twist your body (and knee) too quickly while your feet are on the ground. The pain comes immediately, and not long after, your knee becomes swollen and stiff. And when you bend it, it feels as if something is “catching,” especially if you twist or squat. Your doctor refers you to an orthopaedist, who in turn, diagnoses the problem: a torn meniscus.

Meniscus tears are among the most common knee injuries, and though they occur more often in men, they can affect people of any age and sex. Fortunately, treatments are available for meniscus injuries. They include both conservative, nonsurgical therapies, as well as several types of surgeries.

“Treatment for meniscus tears should be individualized to each patient and be based on the patient’s age, activity level, and the overall condition of the articular cartilage in the knee joint, whether a patient has underlying arthritis or not,” says Christina Allen, MD, chief of Yale Medicine Orthopaedics & Rehabilitation Sports Medicine and head team physician for Yale Athletics.  

There are two menisci (the plural of meniscus) in each knee—one on the lateral (outer) side of the knee, and one on the medial (inner) side. Each meniscus is a thin, “c”-shaped disc of rubbery tissue made of cartilage that is attached to the top of the tibia, or shinbone. The meniscus sits between the tibia and the end of the femur (thighbone), where it functions as a shock absorber between these bones and also contributes to the stability of the knee.

The meniscus is one of two types of cartilage in the knee joint. The other is called articular cartilage, which covers the ends of the tibia, femur bone, and kneecap (patella).

In young, healthy people, meniscus tears often happen as a result of an injury in which the knee rotates or twists while the foot is planted. This kind of injury is known as an acute meniscus tear. It frequently occurs when playing sports such as soccer, football, and basketball that involve pivoting and sharp changes of direction.  

Meniscus tears can also occur when a leg is struck with force while the foot is planted or when lifting a heavy weight. In some cases, meniscus tears are accompanied by injuries to the articular cartilage or ligaments in the knee, such as the anterior cruciate ligament (ACL) and/or the medial collateral ligament (MCL).

In middle-aged and older people, meniscus injuries tend to be degenerative meniscus tears. As people age, the cartilage in the knee, including the meniscus, begins to wear down. As a result, the meniscus becomes more susceptible to injury. Degenerative meniscus tears may occur from everyday activities that do not entail a lot of physical twisting of the knee, such as squatting, planting the foot and turning, or even climbing stairs.

Meniscus tears can occur in various parts of the meniscus and can vary in severity. The majority of meniscal injuries occur in the medial (inner) meniscus, though injuries can also involve the lateral (outer) meniscus.

Depending on its severity, a torn meniscus can cause a variety of symptoms, including the following:

• Knee pain, which may worsen when twisting or bending the knee or squatting
• Swelling overnight following the initial injury
• A “popping” sensation at the time of injury
• Knee-locking, in which the leg cannot fully straighten
• A sensation that the knee is “catching” or "popping" when bending
• The knee “gives out” or feels somewhat unstable
• Stiffness

In some cases, meniscal tears do not produce any symptoms.  

To diagnose meniscus injuries, doctors assess the patient’s medical history, perform a physical exam, and run diagnostic tests.

As an initial step, doctors typically collect information about the patient’s injury history, asking about knee pain and other symptoms, recent physical activity, and whether the patient can point to a specific acute knee injury that initiated symptoms.

During the physical exam, the doctor will check the knee for swelling, pain, and tenderness. The doctor will bend and flex the knee to evaluate range of motion, assess knee ligament stability, and feel for "clicking" or "popping" with meniscus tear tests. He or she may observe the patient’s gait and ask the patient to perform a squat, a “duck walk,” or to stand on the affected leg and twist on it, which may reproduce the meniscus tear symptoms.

In most cases, the doctor will also order an X-ray of the patient’s knee. Sometimes, doctors will order a magnetic resonance imaging (MRI) study to detect injuries and determine the extent of the meniscal damage.

In some cases, diagnosis of a meniscus tear requires arthroscopy, a minimally invasive surgical procedure in which a surgeon makes one or two small incisions on the knee, then inserts an arthroscope (a tiny pencil-sized tube equipped with a camera) and surgical instruments into the knee. The camera captures a video of the inside of the knee, allowing the surgeon to examine structures and tissues, including the meniscus.

In general, with proper treatment and rehabilitation, people who experience meniscus tears, especially older patients, are often able to go back to their normal activities. Still, meniscus tears may increase the risk of developing osteoarthritis, and if left untreated, they can worsen over time.  

However, although meniscectomy is likely to remove pain and "catching" symptoms in an active patient, there is no guarantee that they will not develop osteoarthritis over time due to the loss of some of the shock-absorbing property of the meniscus due to partial removal.

“At Yale Sports Medicine, our surgeons will assess each patient’s history, activity level, knee injury, and activity goals in order to advise them on an individualized treatment plan. Our goal is to treat the patient—not their MRI—and to suggest the best treatment option to allow them to return to their desired activity level while aiming to protect their long-term knee health in the best way possible,” says Dr. Allen. “Whether this means recommending non-operative treatment with physical therapy and cortisone injection, performing a meniscus trimming or repair, or surgically inserting a meniscus transplant of the medial or lateral meniscus, our Sports Medicine surgeons have the skills and expertise to advise and treat patients with these goals in mind.”