An MCL injury happens when a force strikes the outside of the knee. The MCL resists that force, thereby stretching and tearing its fibres. So what are the typical signs of a medial collateral ligament injury, and how do we treat it?
An MCL injury is a common cause of inner knee pain.
What is the medial collateral ligament?
The MCL is one of the four ligaments that stabilise the knee. It’s made of strong, fibrous tissue that resists movement. It runs from the end of the femur (thigh bone) to the top of the tibia (shin), and its main job is to stop the knee from opening up on the inside. A complete tear results in increased knee laxity.
A tear most often occurs at the top attachment to the femur. Sometimes it happens at the lower attachment to the tibia, and tears at the bottom take longer to heal.
How do we diagnose an MCL injury?
The MCL is one of the four ligaments that stabilise the knee. It’s made of strong, fibrous tissue that resists movement. It runs from the end of the femur (thigh bone) to the top of the tibia (shin), and its main job is to stop the knee from opening up on the inside. A complete tear results in increased knee laxity.
A tear most often occurs at the top attachment to the femur. Sometimes it happens at the lower attachment to the tibia, and tears at the bottom take longer to heal.
How do we diagnose an MCL injury?
A medial collateral ligament strain occurs on its own or alongside other ligament or cartilage injuries. The damage happens during sport — bending, turning, or twisting — or from a blow to the outside of the knee that stretches and tears the MCL.
Typical symptoms of an MCL injury include:
- Pain on the inside of the knee
- Localised swelling at the site of the tear
- A feeling of instability or buckling
- Restricted ability to bend or straighten the knee
We grade injuries by severity and how loose the knee is on examination: a grade 1 injury has no laxity; a grade 2 is a partial tear with some laxity; a grade 3 is a complete tear with significant laxity. In some cases, an MRI confirms the MCL damage and rules out injury to other ligaments (such as the ACL) or the meniscus.
MCL injury vs meniscal injury: how to tell
An MCL injury usually occurs at the top attachment to the femur, so pain and swelling are above the joint line. A medial meniscal tear causes pain at the medial joint line, below the MCL’s top attachment, and can cause general swelling, giving way, or locking. Telling them apart needs a careful examination by a specialist.
ACL vs MCL injury
An ACL injury is usually more traumatic and more painful than an MCL injury. People often hear a pop or feel a tear, with significant swelling throughout the knee, and examination shows ACL laxity on testing.
Treatment of an MCL injury
Treatment depends on the grade and severity.
We start simple: regular ice, ibuprofen tablets, and a compression sleeve. Bracing is used for grades 2 and 3 — a hinged or limited-motion brace protects the knee from side-to-side movement, and we sometimes restrict the range from 20 to 100 degrees to let the ligament heal. Braces are typically worn for 4–8 weeks, until stability and strength return. We then move on to mobility exercises to regain movement.
MCL injury exercises
Rehab focuses on strength and balance before a return to sport. Compound exercises such as weighted squats, lunges, deadlifts, incline leg press, and calf raises rebuild knee strength. In the later stages, we progressively add more demanding tasks — jogging, running, sprinting, and side-to-side movements — to reduce the risk of reinjury.
Frequently asked questions about MCL injury
How long does an MCL injury take to heal?
Return to sport depends on the grade: grade 1 takes 2–3 weeks, grade 2 takes 6–8 weeks, and grade 3 takes up to 12 weeks. Other injuries or the demands of your sport can shift these — footballers often take longer, as kicking and side-to-side movements load the MCL. A tear at the lower (tibial) attachment often takes about twice as long as the more common upper tear.
Is an MCL injection helpful?
We rarely use ultrasound-guided injections to help an MCL strain heal. Some doctors use PRP or dextrose, but there’s no evidence that an injection speeds recovery. If we do inject, we use a high-concentration PRP system such as Arthrex ACP Max.
What is Pellegrini-Stieda syndrome (MCL calcification)?
Pellegrini-Stieda syndrome is the calcification of the MCL during healing, with calcium deposits forming at its top attachment, seen on X-ray or ultrasound. People describe gradually worsening stiffness and pain during recovery. Treatment is usually ibuprofen and physiotherapy, sometimes with an ultrasound-guided cortisone injection to break up the calcium. See our full Pellegrini-Stieda lesion page for details.
Is surgery an option for an MCL injury?
Generally no. But surgeons may consider it for a high-grade MCL injury combined with another ligament injury (such as an ACL), a grade 3 tear in an elite athlete, or a tibial attachment tear in which the ligament displaces above the pes tendons (a Stieda injury).
Do we treat an LCL injury the same way?
An LCL injury occurs when the knee bends outward excessively due to trauma or a fall, and is graded like the MCL. Rehab is similar, but with differences: the bracing is set up differently, a grade 3 tear usually requires surgical repair or reconstruction, and LCL injuries are more often associated with other ligament or cartilage damage.
Final word from Sport Doctor London about MCL injury
An MCL injury is a common cause of inner knee pain after a blow or twist to the knee. Most cases settle well with bracing and a structured rehab programme, with surgery rarely needed. See a sports medicine doctor for accurate grading and a return-to-sport plan.
To book a knee assessment with Dr Masci in London, contact the team here or call +44 (0) 203 488 0350.
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