Knee injuries are common. A lateral collateral ligament (LCL) sprain involves damage to tissues on the outer side of the knee. This article explains LCL sprains, their causes, symptoms, and treatment.
Understanding the LCL and a Sprain
The lateral collateral ligament (LCL), also known as the fibular collateral ligament, is a cord-like band located on the outer side of the knee joint. It connects the thigh bone (femur) to the smaller lower leg bone (fibula). The LCL’s primary function is to stabilize the knee by resisting excessive outward bending and sideways motion.
A “sprain” refers to a stretch or tear of a ligament. LCL sprains are categorized into three grades based on their severity. A Grade 1 sprain involves a mild overstretching of the ligament fibers without a significant tear, typically resulting in localized tenderness and pain. A Grade 2 sprain indicates a partial tear of the ligament, leading to more pronounced pain, swelling, and some instability in the knee. The most severe, a Grade 3 sprain, signifies a complete tear of the LCL, often causing significant pain, swelling, and marked knee instability.
How LCL Sprains Happen
LCL sprains typically result from specific forces applied to the knee joint. The most common mechanism involves a direct blow to the inside of the knee, which forces the knee to bend outwards (known as valgus stress). This outward force can stretch or tear the LCL beyond its normal capacity. Hyperextension of the knee, where the joint extends beyond its normal range of motion, can also cause an LCL injury.
Beyond direct impact, LCL sprains can occur during movements involving sudden changes in direction, twisting, or landing awkwardly from a jump. These types of injuries are frequently observed in sports that involve rapid pivoting, cutting, or high-velocity movements. Examples include contact sports like football and soccer, as well as activities such as basketball, skiing, hockey, tennis, gymnastics, and volleyball.
Identifying an LCL Sprain
Recognizing an LCL sprain often begins with specific symptoms experienced after an injury. Individuals commonly report pain on the outside of the knee, which can be accompanied by swelling, tenderness, and stiffness. Some might also describe a feeling that the knee could “give out” or is unstable, particularly with side-to-side movements. A popping sound at the moment of injury is also a reported symptom. If a nerve near the LCL is affected, there might be numbness or weakness extending into the foot and ankle.
A medical professional diagnoses an LCL sprain through a thorough physical examination and imaging studies. During the physical exam, the doctor will assess the knee for pain, swelling, and tenderness around the lateral joint line. A varus stress test, performed by applying an outward force to the knee while it is slightly bent, helps determine the degree of ligament laxity. To rule out fractures or other bone damage, X-rays may be ordered. An MRI confirms the extent of the LCL injury and identifies any other associated ligament or cartilage damage.
Treatment and Recovery
Treatment for an LCL sprain varies based on the injury’s severity. For mild to moderate sprains (Grade 1 and 2), conservative management is the initial approach. This often includes the RICE protocol: Rest, Ice, Compression, and Elevation. Resting the knee limits further injury, applying ice reduces pain and swelling, compression controls swelling, and elevating the leg minimizes it. Nonsteroidal anti-inflammatory drugs (NSAIDs) may be recommended to manage pain and inflammation.
A hinged knee brace may be used to provide stability and protect the joint while allowing some controlled movement during the healing process. Crutches can also be used to limit weight-bearing on the injured leg, especially in the initial stages. Physical therapy is important for recovery across all LCL sprain grades. Rehabilitation exercises focus on restoring the knee’s range of motion, strengthening the surrounding muscles, and improving stability.
For severe Grade 3 LCL sprains, particularly if other knee ligaments are also torn or if there is significant instability, surgical intervention may be considered, although it is less common for isolated LCL injuries. Surgical repair or reconstruction aims to restore the ligament’s integrity and knee stability.
Recovery timelines vary by grade. Mild sprains heal in 2-4 weeks, moderate in 8-12 weeks, and severe can take 8-12 weeks or longer, especially if surgery is performed. Full return to activities, particularly sports, depends on regaining complete strength, stability, and range of motion.