Lateral Collateral Ligament (LCL) Injuries

Your knee depends on multiple structures to maintain stability while supporting your full body weight. Every time you change direction, twist, or land from a jump, it relies on a network of ligaments and tendons to keep everything aligned and moving smoothly.

Located on the outer (lateral) side of the knee, the lateral collateral ligament (LCL) runs like a cord along the outside of the knee to prevent the knee from bowing outward when pressure comes from the inside. Because the LCL works alongside other ligaments and tendons to stabilize the outer side of the knee when the body is in motion, an injury here can disrupt how those other structures function, impacting overall mechanics of the entire knee.

LCL injuries are less common than MCL tears, but they still happen – in athletes during contact sports, in falls, or from sudden twists or high-energy blows to the knee.

Mechanics of an LCL Injury

The LCL connects the lateral femoral epicondyle (outer lower side of the thigh bone) to the head of the fibula (outer upper side of the lower leg). Its job is to resist varus stress (a force applied to the inner knee that pushes it outward away from midline) and to help control how the knee rotates.

The LCL is also part of a group of tissues called the posterolateral corner (PLC). This region is a mix of ligaments and tendons, and when the LCL is injured, these surrounding structures often are, too; LCL tears are fairly uncommon on their own. In fact, true isolated LCL injuries make up less than 2% of knee-ligament cases.¹ They’re more likely to occur with injuries to the PLC, ACL (anterior cruciate ligament), or PCL (posterior cruciate ligament), which can make the knee feel unstable in multiple directions.

Most LCL injuries happen when the ligament is stretched or overloaded beyond what it can handle:

• A high-energy, direct blow to the inside of the knee can force the joint outward.
• A force that pushes the knee into a bow-legged position, even without a collision, can create enough varus stress to injure the LCL.
• Sudden hyperextension, forceful twisting, or non-contact twisting while the lower leg is in an awkward position can strain or tear the ligament.

How to Know the LCL is Injured

LCL injuries range from mild strains (Grade I) to complete tears (Grade III). Because the LCL sits on the outer side of the knee and works closely with other structures in the posterolateral corner, symptoms can sometimes overlap with injuries to nearby ligaments or tendons, making diagnosis more complex.

Most people notice pain along the outer knee, typically near the attachment sites at the fibular head or the lateral femoral epicondyle. Swelling, tenderness, and bruising may develop quickly, and the knee can feel unstable in every direction; some patients describe a sensation that the knee might give way outward or feel like it “collapses” when bearing weight. A telltale sign is the characteristic varus thrust gait, where the knee briefly bows outward with each step.

If your knee feels unstable, swelling is significant, you cannot walk normally, pain persists for more than a few days, or you suspect multiple structures are involved, seek medical evaluation promptly. Because outer-knee tenderness can mimic other conditions, including meniscus or fibular head injuries, a thorough exam and proper imaging are essential for an accurate diagnosis.

Until you can be evaluated by a clinician, the basics of first-aid include:

• The RICE Method
  • Rest: Avoid activities that worsen pain.
  • Ice: Apply in 10-minute intervals; do not leave ice or ice packs on the skin for longer than 15 to 20 minutes at a time.
  • Compression: Lightly wrap to reduce swelling, as long as it does not cause more pain.
  • Elevation: Keep the leg above heart level when possible, and support the joints with bolsters or pillows.
• NSAIDs: Anti-inflammatories such as ibuprofen can help with swelling and pain (if medically appropriate for you).

Diagnosis and Treatment of an LCL Injury

Diagnosis begins with a physical exam and medical history. Your clinician will ask about how the injury occurred and the symptoms you’re experiencing.

During the exam, several tests are used to assess LCL function and detect involvement of surrounding structures in the posterolateral corner (PLC). Physical assessments you might encounter include:

• Varus stress test: the most informative test for LCL stability
• Dial test: used to detect PLC involvement
• Posterolateral drawer test: checks for excessive backward and rotational shift
• External rotation recurvatum test: looks for abnormal hyperextension
• Range of motion measurements: help define a therapeutic baseline

Especially with more complex injuries, imaging can help determine severity and which other structures are involved:

• X-rays rule out fractures or bony avulsions.
• MRI is the gold standard for seeing the ligament fibers and associated structures.
• Musculoskeletal ultrasound can detect fiber thickening, disruption, or dynamic laxity.

Treatment is guided by the severity, or grade, of the injury.

Grade I injuries involve a mild stretch or microscopic tear with localized pain but no noticeable instability. Treatment is typically conservative, and patients are encouraged to follow basic first-aid principles: rest, ice, compression, or NSAIDs to reduce inflammation. A hinged knee brace can add support for a few weeks, and early-range-of-motion exercises can help maintain joint flexibility. Most people recover fully within a month, with minimal risk of long-term complications.

Grade II injuries are partial tears causing more pronounced pain, swelling, and some looseness in the joint that can be felt during an exam. Nonoperative management is typically effective if the injury is isolated (i.e., other structures aren’t involved). Patients may use crutches for a short period and a hinged knee brace for three to six weeks to stabilize the knee while healing. Physical therapy is a likely recommendation to restore motion, strengthen affected muscle groups, and improve neuromuscular control. Recovery generally takes 6 to 10 weeks, with return to full activity once the knee is stable, pain-free, and strength is comparable to the uninjured leg.

Grade III injuries are complete tears and almost always involve other structures in the PLC, causing significant instability and mechanical symptoms. These injuries are pronounced and limit the function of surrounding ligaments, which rely on the LCL for proper stabilization. Because the LCL does not heal reliably on its own, surgical repair or reconstruction is often recommended for Grade III injuries, especially when the tear is acute, involves bony avulsion, or results in persistent varus instability.

Postoperative care typically includes a knee immobilizer for six weeks, followed by structured physical therapy focusing on quadriceps strengthening and protecting the repair. Hamstring strengthening is usually delayed for several months to prevent stress on the reconstruction. Return to sports or high-demand activities can take four to six months, depending on the complexity of the injury and the presence of associated ligament damage.

Risk of re-injury is a concern when patients resume activity too soon or fail to abide by restrictions, neglect muscle strengthening or physical therapy protocols, or have undiagnosed PLC or cruciate ligament involvement. With an accurate evaluation and diagnosis by a skilled practitioner as close to the time of injury as possible, most LCL injuries heal well and patients can regain full function.

From awkward spills to sports accidents, the team at Premier Orthopaedic & Trauma Specialists is ready to get you back on your feet with expert assessment, individualized treatment, and comprehensive rehabilitation.

1. Yaras, R. J., O’Neill, N., Mabrouk, A., & Yaish, A. M. (2024, February 27). Lateral Collateral Ligament Knee Injuries. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK560847/.