Meniscus Injury

A meniscus tear is one of the most common knee injuries, affecting athletes and older adults alike. This injury occurs when the tough, rubbery cartilage that cushions your knee becomes torn, causing pain, swelling, and difficulty moving your knee normally.

Table of contents

• What Is a Meniscus Injury?
• Understanding Knee Anatomy and Meniscus Function
• Types of Meniscus Tears
• What Causes Meniscus Tears?
• Signs and Symptoms
• How Doctors Diagnose Meniscus Tears
• Treatment Options
• Possible Complications

What Is a Meniscus Injury?

A meniscus injury is damage to the tough cartilage inside your knee joint. This injury typically involves a tear in the meniscus, which is a piece of rubbery tissue that acts as a cushion between the bones in your knee^[1]. The tear can happen suddenly during physical activity or develop gradually over time as the cartilage wears down.

Meniscus tears are extremely common, affecting approximately 61 out of every 100,000 people in the United States^[2]. When people talk about torn cartilage in the knee, they are usually referring to a torn meniscus^[3].

Understanding Knee Anatomy and Meniscus Function

• Knee joint
• Femur (thighbone)
• Tibia (shinbone)
• Patella (kneecap)

Your knee joint is formed where two bones meet: the femur (thighbone) and the tibia (shinbone). The kneecap, called the patella, sits in front of the joint to provide protection^[3].

Each knee contains two C-shaped pieces of cartilage called menisci. These wedge-shaped structures sit between your thighbone and shinbone, acting as shock absorbers for your knee^[1]. The meniscus provides cushioning for your bones and knee joint, helping to transmit weight from one bone to another and playing an important role in knee stability^[3].

The meniscus is made of fibrocartilage, a tough and rubbery type of tissue^[3]. One important characteristic of the meniscus is that it has very limited blood supply. Blood vessels only reach the outer portion of the meniscus, while the inner portion receives nutrients by diffusion alone. Because of this poor blood supply, tears of the meniscus usually do not heal on their own^[6].

Types of Meniscus Tears

Each knee joint has two menisci. A medial meniscus tear affects the cartilage on the inside of your knee, while a lateral meniscus tear affects the cartilage on the outside of your knee^[2].

Meniscus tears are classified by how they look and where they occur in the meniscus. Common types of tears include bucket handle tears, flap tears, radial tears, and degenerative tears^[3]. The type and location of the tear affects which treatment approach will work best.

What Causes Meniscus Tears?

The meniscus can tear from sudden injury or as the result of gradual changes that happen over time. There are two main types of meniscus tears based on how they occur: traumatic tears and degenerative tears^[3].

Traumatic tears often happen during sports activities. Any activity that causes you to forcefully twist or rotate your knee, especially when putting your full weight on it, can lead to a torn meniscus^[1]. These tears can occur through either a contact or non-contact injury, such as a pivoting or cutting movement^[3]. The tear frequently occurs while playing sports when your knee twists while your foot stays planted on the ground^[2].

People who play sports that involve sudden, twisting movements—like tennis, soccer, basketball, or football—are most likely to tear a meniscus. Playing contact sports also increases your risk, as getting hit or tackled can make you twist your knee, tearing the cartilage^[2].

Degenerative tears are more common in older people. As people age, they are more likely to have degenerative meniscus tears because aged, worn tissue is more prone to tears^[3]. The cartilage in your knees wears down and gets weaker over time, and this thinner cartilage can tear more easily^[2]. People whose cartilage wears down due to age or arthritis (a breakdown of cartilage in the joints) can tear a meniscus from a motion as simple as stepping on an uneven surface or an awkward twist when getting up from a chair^[2][3].

Sports-related meniscus injuries often occur along with other knee injuries, such as tears of the anterior cruciate ligament (ACL)^[3].

Signs and Symptoms

You might feel a pop when you tear the meniscus. Most people can still walk on their injured knee, and many athletes are able to keep playing with a tear^[3]. At first, you might be able to bear weight on your injured leg, but your knee will start to swell and become more and more painful over the span of a few days^[2].

If you’ve torn your meniscus, it might take 24 hours or more for pain and swelling to begin, especially if the tear is small^[1]. Over 2 to 3 days, however, the knee will gradually become stiffer and more swollen^[3].

The most common symptoms of a meniscus tear include:

• A popping sensation at the time of injury
• Pain, especially when twisting or rotating your knee^[1]
• Knee pain or stiffness^[2]
• Swelling around your knee^[1]
• Difficulty straightening your knee fully or being unable to fully bend or straighten your leg^[1][2]
• Feeling as though your knee is locked in place when you try to move it^[1]
• Catching or locking of your knee^[3]
• The sensation of your knee giving way beneath you^[2][3]
• Inability to move your knee through its full range of motion^[3]

Contact your doctor if your knee is painful or swollen, or if you can’t move your knee in the usual ways^[1].

How Doctors Diagnose Meniscus Tears

A torn meniscus often can be identified during a physical exam^[7]. Your healthcare provider will physically examine your knee, looking for signs of swelling. After discussing your symptoms and medical history, your doctor will examine your knee and check for tenderness along the joint line where the meniscus sits, which often indicates a tear^[2][3].

Your doctor might move your knee and leg into different positions, watch you walk, and ask you to squat to help pinpoint the cause of your signs and symptoms^[7]. They’ll test your range of motion using specific tests like the McMurray test or Thessaly test^[2].

One of the main tests for meniscus tears is the McMurray test. Your doctor will bend your knee, then straighten and rotate it. This movement can produce a clicking sound or sensation if you have a meniscus tear^[3].

You may also get imaging tests to assess the damage:

• X-rays: Because a torn meniscus is made of cartilage, it won’t show up on X-rays. However, X-rays can help rule out other problems with the knee that cause similar symptoms, such as fractures or arthritis^[7][6].
• Magnetic resonance imaging (MRI): This uses a strong magnetic field to produce detailed images of both hard and soft tissues within your knee. It’s the best imaging study to detect a torn meniscus^[7]. Meniscus is shown on an MRI as a series of slices that resemble black triangles, and tears appear as an area of white signal through the meniscus tissue^[6].
• Arthroscopy: In some cases, your doctor might use an instrument known as an arthroscope to examine the inside of your knee. The arthroscope is inserted through a tiny incision near your knee and contains a light and a small camera, which transmits an enlarged image of the inside of your knee onto a monitor^[7][2].

Treatment Options

Treatment for a torn meniscus often begins conservatively, depending on the type, size, and location of your tear^[7]. Some tears may feel better on their own with home care and rehabilitation, while others may require surgery^[5].

Non-Surgical Treatment

Tears associated with arthritis often improve over time with treatment of the arthritis, so surgery usually isn’t indicated. Many other tears that aren’t associated with locking or a block to knee motion will become less painful over time, so they also don’t require surgery^[7].

Initial treatment often includes:

• Rest: Avoid activities that aggravate your knee pain, especially any activity that causes you to twist, rotate, or pivot your knee. If your pain is severe, using crutches can take pressure off your knee and promote healing^[7].
• Ice: Ice can reduce knee pain and swelling. Put ice or a cold pack on your knee for 10 to 20 minutes at a time, trying to do this every 1 to 2 hours for the next 3 days or until the swelling goes down^[7].
• Compression: Wrap a bandage around your knee or wear a knee support^[5].
• Elevation: Prop up the sore leg on a pillow, trying to keep your leg above the level of your heart to help reduce swelling^[5].
• Pain medication: Anti-inflammatory medications, both non-steroidal and steroids, can be very effective in decreasing inflammation and pain. Other pain relievers, such as paracetamol, may also be helpful^[5].
• Physical therapy: Rehabilitation exercises to strengthen the muscles around the joint can be very helpful. A structured physical therapy program may be recommended to help reduce pain and improve movement and strength in the knee^[5][9].

There is evidence suggesting that degenerative tears in older patients without mechanical symptoms can be effectively treated non-operatively with a structured physical therapy program as a first line^[9].

Other non-surgical options may include injections. The most common type is a corticosteroid injection, which decreases inflammation and can be very helpful in controlling pain^[17].

Surgical Treatment

Because of the poor healing capacity of the meniscus, most symptomatic meniscus tears caused by trauma require arthroscopic surgical treatment^[6]. If the damage is severe, you may need arthroscopy surgery to repair or remove the damaged cartilage^[5].

Surgical instruments can be inserted through the arthroscope or through additional small incisions in your knee to trim or repair the tear^[7]. Meniscus surgery often falls into two categories: repair or removal^[17].

At the time of surgery, your surgeon will make a determination of whether or not the meniscus tear is repairable. Complex tears and degenerative tears are usually not amenable to repair and are treated with arthroscopic partial meniscectomy (removal of the torn piece)^[6]. Partial meniscectomy is suitable for symptomatic tears not amenable to repair and can still preserve meniscal function, especially when the peripheral meniscal rim is intact^[9].

Meniscal repair is more suitable in younger patients with reducible tears that are peripheral (nearer the capsular attachment) and horizontal or longitudinal in nature. Meniscal repair shows 80% success at 2 years^[9]. However, careful patient selection and repair technique is required with good compliance to post-operative rehabilitation, which often consists of bracing and non-weight bearing for 4-6 weeks^[9].

All efforts are made to preserve as much meniscus tissue as possible, as the meniscus functions primarily as a shock absorber and helps to protect the cartilage of the knee^[6].

Possible Complications

If your meniscus tear doesn’t heal properly, you may have continued pain and discomfort in your knee. Meniscus injury can also speed up the wear and tear on your knee joint, increasing your risk for osteoarthritis^[2]. Even if these patients later require meniscectomy, they will still achieve similar functional outcomes than if they had initially been treated surgically^[9].