While the term “strain” is sometimes used loosely to describe any mild injury, the meniscus itself is a fibrocartilaginous structure that does not strain in the same way a muscle or tendon does. The more accurate and medically accepted term for an injury to the meniscus is a “tear” or “rupture.” Strains involve the overstretching or tearing of muscle or tendon fibers, whereas meniscal injuries involve a disruption in the cartilage tissue. This article will clarify the fundamental difference in terminology and explain the mechanics and treatment of actual meniscal injuries.
The Meniscus Role in Knee Stability
The knee joint contains two menisci: the C-shaped medial meniscus on the inside of the knee and the more circular lateral meniscus on the outside. These structures are composed primarily of fibrocartilage, a tough, rubbery tissue that provides both flexibility and strength. They are positioned between the rounded bottom of the thigh bone (femur) and the flat top of the shin bone (tibia).
The menisci serve multiple functions, acting like specialized gaskets within the joint. Their wedge shape helps to increase the contact area between the two bones, which is primary for distributing the forces applied to the knee. This load distribution function is substantial, as the menisci transmit 50% to 90% of the total axial load across the knee joint during weight-bearing activities. They also act as shock absorbers, dampening impact forces. They contribute significantly to the stability of the knee. When this structure is compromised, the forces on the articular cartilage increase, which can lead to long-term joint wear and potential osteoarthritis.
Understanding Meniscal Tears Versus Strains
A “strain” refers to damage in a musculotendinous unit, which is tissue designed to stretch and contract. The meniscus, being fibrocartilage, is not contractile and is instead damaged by mechanical tearing forces that exceed its tensile strength. Therefore, injuries to this tissue are accurately classified as tears, which range from small fraying to complete ruptures.
The shape and direction of the tear determine its classification. Common types include radial, horizontal, and longitudinal tears. A severe form of a longitudinal tear is the “bucket-handle” tear, where a segment of the cartilage flips into the joint space, often causing mechanical symptoms.
The healing potential of a meniscal tear is directly related to its location and blood supply. The outer third of the meniscus, known as the “red-red zone,” receives a blood supply from the capsule and has the highest capacity for healing. The inner two-thirds, or “white-white zone,” is largely avascular. Tears in this area have a very low potential for spontaneous healing because the necessary blood cells and nutrients cannot reach the injury site.
Identifying Symptoms and Injury Mechanisms
Meniscal injuries can occur acutely from a single traumatic event or develop gradually due to chronic degeneration. Acute tears often happen during sports that involve sudden, forceful twisting or pivoting motions while the foot is firmly planted on the ground. This mechanism traps the meniscus between the femur and tibia, causing it to rip.
In older adults, degenerative tears are more common, resulting from cumulative wear and tear over time. These can sometimes occur with minimal trauma, such as simply standing up from a squatting position or an awkward twist. The cartilage weakens with age, making it susceptible to tearing under normal loads.
Symptoms typically include localized pain along the joint line, which is the space between the bones where the meniscus sits. A patient may recall a distinct “pop” at the time of injury, followed by swelling that can develop over several hours. A hallmark sign of a mechanically significant tear is “locking,” where a torn fragment of cartilage physically blocks the knee from fully straightening or bending, or a sensation of “catching” during movement.
Pathways for Diagnosis and Recovery
Following a suspected meniscal injury, initial self-care involves following the RICE protocol: Rest, Ice, Compression, and Elevation. Rest means avoiding activities that aggravate the knee, and using crutches may be recommended to take pressure off the joint. Applying ice for about 20 minutes several times a day helps to reduce pain and swelling.
A medical professional will perform a physical examination, checking for tenderness along the joint line and testing the knee’s range of motion. Specific maneuvers, like the McMurray test, involve flexing, extending, and rotating the knee to reproduce a painful clicking or clunking sensation, which can indicate a tear. X-rays are typically ordered to rule out associated bone fractures. Because the meniscus is soft tissue, a Magnetic Resonance Imaging (MRI) scan is the most definitive imaging tool for diagnosing the location and type of tear.
Treatment paths are determined by the tear’s size, location, and the patient’s symptoms. Many minor tears, especially degenerative ones or those in the vascular outer zone, are managed conservatively with physical therapy and time. Physical therapy focuses on restoring full mobility and strengthening the muscles surrounding the knee joint. If symptoms like persistent pain, instability, or mechanical locking continue, surgical options are considered. These options include meniscal repair for tears in the vascular zone or partial meniscectomy, which removes only the unstable, torn fragment.