The meniscus is a C-shaped piece of cartilage that functions as a shock absorber and stabilizer within the knee joint; the lateral meniscus sits on the outer side of the knee. A torn lateral meniscus is often confusing because the damage is internal, making the outward appearance subtle or delayed. Tears frequently occur from twisting movements or sudden impact, varying widely depending on the severity and whether other structures were injured. This information provides a general understanding of the injury’s signs, but it is not a substitute for a professional medical diagnosis.
Visible Signs of a Lateral Meniscus Tear
The most common outward sign of a lateral meniscus tear is swelling, though its appearance can be deceptive. Swelling usually develops gradually over several hours to a couple of days following the injury, unlike the instant swelling seen with severe ligament tears. This fluid accumulation may make the knee joint look generally puffy and feel stiff.
The swelling may localize more prominently over the outer (lateral) joint line. This localized puffiness occurs where the damaged cartilage fragment irritates the joint lining. The knee may also feel warm to the touch and appear slightly red due to the underlying inflammatory response.
Bruising is often absent or minimal with an isolated meniscus tear. The meniscus has a limited blood supply, so a tear does not always cause blood to leak into surrounding tissues. Significant bruising often suggests that other structures, such as ligaments or bone, were also injured during the initial trauma.
Subjective Symptoms That Accompany the Injury
Subjective symptoms are typically more telling than mild visible signs. A sharp, localized pain along the lateral joint line is a hallmark symptom of a lateral meniscus tear. This pain often intensifies when the knee is twisted, rotated, or forced into a deep squatting position.
The most indicative symptoms are mechanical, resulting from the torn cartilage interfering with normal joint movement. These include sensations of clicking, popping, or catching within the knee joint during motion. A severe tear, such as a “bucket-handle” tear, can cause the knee to “lock,” meaning the inability to fully straighten the leg because the torn fragment physically obstructs the joint.
The person may also report instability, where the knee feels weak or prone to “giving way” during activities like pivoting or walking on uneven ground. This buckling sensation occurs because the damaged cartilage affects the joint’s stability and proprioception (the body’s sense of joint position). Limited ability to fully bend or straighten the leg, often accompanied by stiffness, further restricts everyday movements.
Immediate Steps Following a Knee Injury
Following a suspected lateral meniscus tear, the immediate priority is to prevent further damage and manage initial symptoms using the RICE principle. Rest and protect the knee by avoiding weight-bearing, twisting, or pivoting movements. Consider using crutches if walking causes pain.
Apply Ice to the outer knee for 15 to 20 minutes every couple of hours, using a thin cloth between the ice and skin. Gentle Compression, such as an elastic bandage, helps minimize swelling, but avoid wrapping so tightly that it causes numbness. Elevating the leg above the heart level while resting also helps control fluid accumulation.
Over-the-counter anti-inflammatory medications may manage pain and swelling, but discuss any medication regimen with a healthcare provider first. These measures provide temporary relief and support while waiting for a professional medical evaluation, and are not a substitute for a definitive diagnosis or long-term treatment plan.
Confirming the Diagnosis
Confirming a lateral meniscus tear requires a professional evaluation, as external signs overlap with other knee conditions. A healthcare professional begins with a physical examination, focusing on reproducing mechanical symptoms. Tenderness along the lateral joint line is a sensitive indicator of a tear in that area.
Specific physical tests, such as the McMurray or Thessaly tests, are performed to isolate the meniscus. These maneuvers involve flexing, rotating, and extending the knee while applying pressure. A positive result is indicated by a painful click or pop.
Imaging studies are used to confirm the diagnosis. X-rays are often performed first to check for associated bone fractures or arthritis, but cartilage does not show up on them. Magnetic Resonance Imaging (MRI) is the definitive tool for visualizing the meniscus and surrounding soft tissues. An MRI accurately shows the location, size, and type of the tear, providing necessary detail for a precise diagnosis.