Pain on the inside of the knee after a knock or an awkward twist is often a sign of an injury to the medial collateral ligament, or MCL. It can make the knee feel sore, swollen and, at times, a little unstable, which is unsettling. The reassuring part is that most MCL injuries settle well with the right approach.
The medial collateral ligament is a strong band on the inside of the knee that connects the thigh bone to the shin bone, and it helps stop the knee from buckling inwards. An MCL injury happens when a force pushes the knee inwards further than the ligament can tolerate, so the ligament is overstretched, or partly or fully torn.1
This article explains what an MCL injury is, how it happens, how it is graded, how it is assessed, and how it is treated, along with when it is worth being seen in person.
The Short Version
An MCL injury affects the ligament on the inside of the knee. It usually happens in a one-off incident, such as a knock to the outside of the knee or an awkward twist or landing. It is graded 1 to 3 by how stable the knee is when tested. Most isolated MCL injuries, including many complete tears, recover well without surgery through protected movement, a brace where it is needed, and progressive strengthening. Surgery is mainly considered when other ligaments are also injured. See someone promptly if the knee locks, cannot take weight, or feels severely unstable.
Dealing with inner-knee pain or a knee that feels unstable? A proper assessment can work out what is driving it and the best way forward.
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Chat on WhatsAppWhat Is an MCL Injury?
The medial collateral ligament runs along the inside of the knee and helps keep it stable, stopping it from buckling inwards when you walk, run or turn. An MCL injury means this ligament has been overstretched, or partly or fully torn.
MCL injuries are usually caused by a one-off event rather than something that builds up slowly. A hit to the outside of the knee, an awkward twist or a bad landing can push the knee inwards and strain the ligament. This is common in contact and pivoting sports, but it can also happen in a fall or a misstep.1
Common Signs and Symptoms
You may notice some or all of these:
- Pain on the inside of the knee, especially with movement or putting weight through the leg.
- Swelling around the knee, which may come on soon after the injury.
- Tenderness when you press on the inner side of the knee.
- A feeling that the knee is loose or wobbly, or that it might give way.
- Pain or stiffness when bending or straightening the knee.
- Sometimes a “pop” felt at the moment of injury, and bruising over the following day or two.
How Bad Can an MCL Injury Be?
MCL injuries are graded by how stable the knee is when it is tested:1
- Grade 1, mild sprain: a small number of ligament fibres are injured, but the knee remains stable when tested. There is usually tenderness on the inside of the knee and little swelling.
- Grade 2, partial tear: more fibres are torn and the knee may be slightly loose when tested. Pain, swelling and difficulty with turning or stairs are usually more noticeable.
- Grade 3, complete tear: the ligament is fully torn and the knee is clearly loose when tested. It may feel unstable, and putting weight through the leg can be difficult at first.
Milder MCL injuries often settle over several weeks. More significant tears usually take longer, particularly when another ligament or the meniscus was also injured. Progress is judged by improvements in pain, swelling, movement, knee stability and function rather than one exact deadline.
What Other Conditions Could It Be?
Medial Meniscus Tear
A tear of the cartilage inside the knee, often from a twist. Like an MCL injury it can cause inner-knee pain and swelling, but it more often causes catching, clicking or a sense of the knee getting stuck.
Anterior Cruciate Ligament (ACL) Tear
Often from a sudden stop, pivot or awkward landing, an ACL tear tends to cause a pop, rapid swelling and a marked feeling of the knee giving way. An ACL and an MCL injury can happen at the same time, which changes the management, so both are checked during an assessment.5
Patellofemoral Pain Syndrome
A dull ache around the front or inside of the knee that usually builds up over time with running, squatting or prolonged sitting. Unlike an MCL injury, it is not linked to a single incident and does not cause the knee to feel unstable.
Pes Anserine Bursitis
Irritation of a small fluid-filled sac just below the inner knee, causing pain and tenderness a little lower than the MCL, usually without the knee feeling unstable.
Medial Plica Syndrome
Irritation of a small fold of tissue inside the knee, which can cause clicking, catching and inner-knee pain with movement, usually without the swelling or instability of a ligament injury.
Common Mistakes When Managing an MCL Injury
Pushing Straight Back into Aggravating Loads
Returning to cutting, pivoting or sideways stress too soon tends to keep the knee irritated. Easing those loads early, while keeping the knee moving within comfortable limits, gives it a better chance to settle.
Resting Completely and Avoiding All Movement
Complete rest can leave the knee stiff and the surrounding muscles weaker. Gentle, protected movement early on is usually better than doing nothing, with loading built up gradually.
Returning to Sport Before the Knee Is Ready
Going back to sport before strength, control and confidence have returned can flare the knee or lead to another injury. A gradual, monitored return works better than a fixed date on the calendar.
What to Expect During Recovery
Most isolated MCL injuries recover well. Early on, it helps to reduce activities that place sideways stress on the knee while keeping it moving within comfortable limits. Strengthening and balance work are then progressed as pain, swelling and stability improve. An assessment is useful when the knee remains unstable, symptoms are not improving, or you are unsure when to increase activity.2
When to Have Your Knee Checked in Person
Most MCL injuries can be managed well, but a few situations are worth checking in person.
Have the knee assessed promptly after a significant injury if:
- it is physically locked and will not straighten
- you cannot put weight on the leg
- it feels severely unstable
- or it becomes very swollen quickly
Arrange an assessment if:
- the knee repeatedly gives way
- pain on the inside of the knee is limiting walking or stairs
- movement remains restricted
- or symptoms are not improving with sensible activity changes
When Are Scans Needed?
An MCL injury is usually identified from what happened, where the knee hurts and how stable it is during an examination. A scan is not always needed. An MRI may be used to show the ligament injury more clearly and to check for damage to the ACL, meniscus or other parts of the knee. An X-ray may be used when a fracture needs to be ruled out. Scan findings are interpreted alongside your symptoms and examination.4
Is Surgery Needed?
Most isolated MCL tears are treated without surgery. An orthopaedic opinion may be needed when other ligaments are also injured,5 the torn ligament has moved out of position, or the knee remains clearly unstable after rehabilitation.6 A complete tear by itself does not automatically mean that surgery is needed.
Treatment Options
Treatment is individualised and guided by your assessment. Protected early movement, load management and progressive strengthening are the core, and the options below are used alongside them to keep you comfortable and moving.
Exercise and Load Management
This is the cornerstone. Progressive strengthening, balance work and a gradual return to activity help rebuild strength, control and confidence around the recovering knee.3
Bracing
A hinged knee brace is often helpful for a more significant MCL tear. It protects the inside of the knee from sideways stress while still allowing safe, controlled movement. Whether you need one, and how long you wear it, depends on how stable the knee is and whether anything else was injured.2
Myofascial Release
This can ease discomfort in tight or sensitive muscles around the knee and make movement and exercise more comfortable.
Orthopaedic Manual Therapy
Hands-on treatment can provide short-term relief of stiffness and help the knee move more comfortably alongside rehabilitation.
Laser Therapy
I may use laser as a modest extra for comfort during rehabilitation. It does not replace exercise and progressive loading.
Dry Needling
This may ease muscle-related discomfort around the knee and make movement more comfortable for some people.
Taping and Strapping
These can provide temporary support and comfort while strength and activity are gradually rebuilt.
Frequently Asked Questions
Do I need surgery for an MCL tear?
Most isolated MCL tears do not need surgery, including many complete tears. Surgery is mainly considered when other ligaments are also injured, the torn ligament has moved out of position, or significant instability remains after rehabilitation.
Should I wear a brace?
A hinged brace is often helpful for a more significant tear, to protect the knee while allowing safe movement. Milder strains may not need one. Your assessment guides this.
Can I keep walking or training?
Usually within comfortable limits, and often with early protected movement rather than complete rest. Sideways stress, cutting and pivoting are eased at first and reintroduced gradually.
How long does it take?
It varies with the grade, any other injuries and your goals. Milder injuries often settle over several weeks; more significant tears take longer. Progress is judged by pain, swelling, movement, stability and function rather than a fixed timeline.
Will my knee be stable again?
Most people rebuild a stable and confident knee with appropriate protection, strengthening and control work. If the knee continues to give way, it should be reassessed to check whether another structure was injured.
Conclusion
An MCL injury does not have to keep you from the activities you value. Most isolated injuries recover well with protected early movement, a brace where it is needed, and progressive strengthening. Recovery takes time and varies from person to person, but steady progress is a realistic goal with a clear plan. If inner-knee pain or instability is holding you back, an assessment can work out what is going on and set the next steps.
Ready to take the next step? Book a session at Daniel da Cruz Physiotherapy in Sandton.
About the Author
Daniel da Cruz is a physiotherapist in Sandton, registered with the HPCSA. He holds a Bachelor of Physiotherapy (BPhysT) from the University of Pretoria and works with active people managing knee and lower-limb pain, including ligament injuries such as MCL tears, using assessment, graded exercise and hands-on treatment. He combines evidence-based rehabilitation with practical advice to help people move more comfortably and return to the activities they value.
References
- Naqvi U, Sherman AL. Medial Collateral Ligament Knee Injury. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2023 Jul 17. https://www.ncbi.nlm.nih.gov/books/NBK431095/ ↩
- Svantesson E, Piussi R, Weissglas E, Karlsson J, et al. Shedding light on the non-operative treatment of the forgotten side of the knee: rehabilitation of medial collateral ligament injuries – a systematic review. BMJ Open Sport & Exercise Medicine. 2024;10(2):e001750. https://doi.org/10.1136/bmjsem-2023-001750 ↩
- Roberts SB, Brown OS, Beattie N, Brown GSC, Maempel JF, White T. Systematic review of randomised controlled trials for interventions to treat injuries to the medial ligaments of the knee. The Surgeon. 2021;19(2):111–118. https://doi.org/10.1016/j.surge.2020.03.003 ↩
- Meyer P, Reiter A, Akoto R, Bouillon B. Imaging of the medial collateral ligament of the knee: a systematic review. Archives of Orthopaedic and Trauma Surgery. 2022;142(12):3721–3736. https://doi.org/10.1007/s00402-021-04200-8 ↩
- Grant JA, Tannenbaum E, Miller BS, Bedi A. Treatment of combined complete tears of the anterior cruciate and medial collateral ligaments. Arthroscopy. 2012;28(1):110–122. https://doi.org/10.1016/j.arthro.2011.08.293 ↩
- DeLong JM, Waterman BR. Surgical repair of medial collateral ligament and posteromedial corner injuries of the knee: a systematic review. Arthroscopy. 2015;31(11):2249–2255.e5. https://doi.org/10.1016/j.arthro.2015.05.010 ↩
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