A lateral collateral injury is an injury to the lateral collateral ligament (LCL) in the knee joint. These may range from ligament strains, in which the connective fibers making up the ligament are overstretched, to a partial or complete tear, also known as a rupture. Symptoms of a lateral collateral injury are felt on the outside of the knee joint, where the ligament is located, and consist of pain and swelling at the injury site, discomfort under tension or during movement, tenderness upon palpation of the ligament, and knee instability and weakness.
Also known as the fibular collateral ligament as it is found on the same side as the fibula bone in the lower leg, the LCL is situated to the outside of the knee joint. It is considered an extracapsular ligament in that it is located outside of the joint capsule. Running vertically and slightly backward down the side of the knee, the LCL originates on the lateral epicondyle of the femur, the rounded bony protrusion at the base of the femur bone on the outside of the thigh, just above and to the outside of the knee. It then attaches to the lateral surface of the head of the fibula, just below and to the outside of the knee. This ligament is somewhat free-floating along the side of the knee, in that it is not connected along its length to any internal structures of the joint, and as such it is relatively vulnerable to a lateral collateral injury.
An LCL injury typically occurs in three ways. It can happen from a direct blow to the leg, specifically to the inside of the knee, as in contact sports. In soccer, for instance, a kick or collision that pushes the knee outward, thus stretching the LCL past its normal range, can lead to a strain or tear. Another cause of lateral collateral injury is a non-contact injury caused by a sudden movement, such as twisting or falling. These can happen among athletes, such as football players who make abrupt cutting motions, or among the elderly, who may be susceptible to joint injury upon falling. A final cause of LCL injury is from overuse over time, as in athletes who mildly overstretch the ligament during frequent, repetitive movements, which can lead to strains or gradual tearing.
Symptoms of these injuries can range from mild to acutely felt, depending on the severity of the injury. A mild ligament strain may present with some pain at the site, tenderness to the touch, and perhaps stiffness at the outside of the knee. On the other hand, an individual who has sustained a rupture will likely experience more severe pain, swelling, difficulty in moving the knee, stiffness, and, notably, a sense of instability at the joint as if the knee will give out. In addition, a rupture may lead to weakness or numbness in the foot, if the peroneal nerve located near the LCL and running down the outside of the leg to the foot is damaged by the lateral collateral injury.