LCL injury often causes pain and tenderness on the outside of the knee, especially after a side impact, awkward landing, or sudden change of direction. The lateral collateral ligament (LCL) helps resist “varus” force (the knee bowing outward) and supports stability during cutting, pivoting, and deceleration.

Although isolated LCL injuries are less common than some other ligament injuries, they still matter. They can occur alone or alongside other structures, including the posterolateral corner (PLC). For broader context, start with the knee ligament injury guide and the knee pain causes guide.

Next, keep in mind that “outer knee pain” does not always mean an LCL problem. Overuse issues like ITB syndrome or joint problems such as the superior tibiofibular joint (STFJ) can feel similar. A clear assessment helps you avoid the wrong rehab plan.

What causes an LCL injury?

LCL injuries most often happen when a force pushes the knee from the inside to the outside. That can occur during contact sport (a tackle or collision), a fall, or a misstep off a curb. Sometimes, the LCL also strains during twisting injuries when the foot stays planted and the knee rotates.

Common symptoms

• Pain, tenderness, or bruising on the outside of the knee
• Swelling (sometimes mild in isolated LCL sprains)
• A feeling the knee may “give way”, especially with cutting or downhill walking
• Pain with side-to-side movement, running, or stairs
• Difficulty trusting the knee in sport or quick direction changes

How serious is it? LCL injury grading

Clinicians often grade LCL injuries based on laxity and symptoms:

• Grade I (sprain): mild pain, minimal laxity, and often a quicker return to activity.
• Grade II (partial tear): more pain and tenderness, noticeable looseness, and a longer rehab phase.
• Grade III (complete tear): significant instability, and higher risk of combined injury (including PLC involvement).

Diagnosis and testing

A physiotherapist will ask about the mechanism of injury, then assess swelling, range of motion, strength, and stability. Tests such as the varus stress test can help assess lateral stability. Your clinician may recommend imaging if needed. For example, MRI can help clarify whether the injury is isolated or part of a multi-structure pattern.

External authority: Penn Medicine’s overview of LCL injury assessment and management is a useful general reference: Lateral collateral ligament (LCL) injury.

People also ask: can you walk on an LCL tear?

Many people can still walk with an LCL injury, particularly Grade I or mild Grade II sprains. However, walking does not confirm it is “minor”. If you feel instability, worsening swelling, or sharp lateral knee pain with direction change, you may need a more structured plan and activity changes to protect healing tissues.

Healing time and return to sport

Recovery depends on severity, associated injuries, and how well the knee tolerates load. Many Grade I injuries settle over a few weeks. Grade II injuries often need a longer rehab block. Grade III injuries may require orthopaedic input, particularly if instability persists or if there is suspected PLC or cruciate ligament involvement.

During rehab, your plan usually progresses from settling pain and swelling, to restoring motion, then rebuilding strength and control. Finally, sport-specific drills, deceleration, cutting, and confidence work guide return to training and competition. For broader guidance on training loads and return to sport planning, see Sports Physiotherapy Brisbane and sports injury physiotherapy.

Physiotherapy treatment for an LCL injury

Your treatment plan depends on the grade and your goals. A physiotherapist may recommend:

• Relative rest and activity modification to settle irritation
• Targeted strengthening (often hips, lateral chain, and knee stabilisers)
• Balance and agility drills to restore control
• Running progressions and change-of-direction retraining when appropriate
• Advice on bracing or taping if instability limits function

If you also have broader ligament involvement, your clinician may direct you to related education pages, such as PCL injury and general information on ligament tear recovery.

Preventing recurrence

Re-injury risk drops when strength, control, and sport capacity match your demands. Many people benefit from a plan that includes lateral strength, landing mechanics, deceleration control, and graded return to pivoting tasks. In addition, good footwear and training load management can reduce avoidable flare-ups.

What to do next

• If you have new instability, rapid swelling, or pain with twisting, book an assessment soon.
• If pain persists beyond 7–10 days, or you cannot trust the knee for daily tasks, get a clear diagnosis before pushing training.
• If your symptoms worsen with return to running or cutting, you may need a staged return-to-sport plan.

References

1. Haslhofer DJ, et al. Isolated clinically diagnosed grades 1–2 lateral collateral ligament injuries in elite athletes do not require surgery. Orthop J Sports Med. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC12669863/
2. Abu-Mukh A, et al. Exploring the posterolateral corner of the knee joint. 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC11899980/
3. LaPrade RF, et al. A contemporary international expert consensus statement on evaluation, diagnosis, treatment, and rehabilitation of posterolateral corner injuries. 2025. https://www.arthroscopyjournal.org/article/S0749-8063%2825%2900352-4/abstract