Meniscal Injuries

The menisci, the medial (inner) and the lateral (outer), are two wedge-shaped fibrocartilaginous structures of the knee joint that have the paramount functions of supporting the load transmission between structures, providing shock absorption, and enhancing knee stability by improving the congruency of the joint itself. An interesting feature of menisci is that the outer parts are more vascularized than the inner parts, an aspect that becomes relevant in the management of these injuries. The most common meniscal injury mechanisms consist of a twisting motion performed with a semi-flexed knee, a frequent mechanism during high-intensity activities such as in multidirectional sports (e.g., soccer, basketball, skiing, etc.). Because of this mechanism (high-energy knee rotation), patients who are injured in this way tend to have associated injuries, especially to the knee ligaments, especially the anterior cruciate ligament and medial collateral ligament. Although less common, medial/lateral meniscus injury can also occur in forced knee flexion actions, when the patient rapidly bends the knees under load through a large movement (e.g., squat, landing from a fall, etc.). Although not the primary mechanism of injury, low-energy meniscal injuries are also possible, injuries that are most commonly reported in the elderly, where degenerative changes (e.g., osteoarthritis) or repeated stress over time (“wear and tear”) may have already contributed to reduced structural tolerance of the meniscus. Meniscus injuries tend to be classified according to their direction of injury (horizontal, longitudinal, radial, bucket-handle, flap, and complex injuries) and each has specific different implications for their management. Symptoms of a meniscus rupture can vary significantly among individuals depending on the mechanism of injury, the presence of associated injuries, and the type/location of the injury itself. Common symptoms include swelling, pain, clicking, and potential locking of the joint with associated inability to flex or extend the knee.