Updated: Jul 12
An MCL sprain – an injury to the medial collateral ligament, on the inside of your knee – can be caused by a sudden impact to the leg, or it can develop over time due to the way you walk or run. This article explains how the MCL sprain treatment will depend on how the injury happened, as well as what the symptoms are and what the expected recovery times are. Remember, if you need more help with an injury, you're welcome to consult one of our physios online via video call.
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We’ve also made a video about this:
Anatomy of the medial collateral ligament
In spite of the singular “ligament” in the name, the MCL consists of three parts, and one of them has been discovered only relatively recently!
These ligament parts are on the inside of your knee, and they attach the bottom end of your thigh bone (femur) to the top end of your shin bone (tibia). Their job is to prevent the inner part of your knee joint from separating as you move.
When I studied physiotherapy about twenty years ago, we knew about the superficial MCL (sMCL in Picture A) and the deep MCL (the only ligament in Picture B). Since then, they have also discovered the posterior oblique part of the ligament (POL in Picture A).
Causes of MCL sprains
MCL sprains are caused by forces that want to make the knee collapse inwards and that are stronger than what the MCL can handle. It can be a sudden force or something more ongoing that sets in over time.
Sudden MCL sprains
These are typically caused by an impact to the outside of the leg that forces the knee joint inwards, causing an MCL sprain.
A sudden MCL sprain could also happen without an impact to the leg, for example if you step off the pavement awkwardly or step in a hole.
Overuse MCL sprains
These happen when there is something about the way you walk and/or run that causes the inside of the knee to take more strain than it is meant to, instead of having the forces of walking and running distributed more “fairly” throughout the whole joint.
The most common examples are when you don’t have good stability around your pelvis due to weak gluteal muscles or when your foot collapses inwards too much (over-pronation). In both cases, this can cause your knee to turn in excessively and increase the strain on the MCL.
For runners and walkers, the pain from this overuse type of MCL sprain develops slowly over time.
It is quite important to understand what has caused an overuse MCL sprain, because you should address these causes during your rehab.
MCL sprain grades
Grade 1 is a very minor sprain. You will usually have some pain but the knee will be stable.
Grade 2 means that a substantial number of fibres have been torn. You will have more pain and your knee will be a little less stable.
Grade 3 means that the ligament is fully ruptured. Interestingly, Grade 3 tears are often less painful than Grade 2 ones, but your knee will be a lot less stable.
MCL sprain symptoms
You feel a sudden, sharp pain on the inside of your knee while doing an activity.
Depending on how severe your sprain is, you may struggle to fully bend or straighten your knee.
The pain is located over the inner part of the knee and, when pressing on the MCL, you can find a painful portion in the ligament.
Activities that cause your knee to turn in or gap on the inner part usually cause pain, e.g. walking on uneven terrain or soft sand, walking in unstable or too flexible shoes, or twisting around while your feet are planted.
You may notice a bit of swelling over the inner part of your knee joint, in the area of the ligament. Isolated MCL sprains don’t cause much swelling. If your knee swells significantly, you’ve likely also injured something else inside your knee, e.g. your meniscus.
If you’ve torn a significant part of your MCL, your knee may feel unstable when you walk.
Overuse MCL sprains
The pain usually develops gradually over time and you’re not aware of any specific moment when you injured your knee.
The pain is also located over the inner joint line, and you can find a painful area in the MCL when you press on it with your fingers.
You may be able to fully bend and straighten your knee without any pain.
Your pain will be aggravated by activities that increase the strain on the MCL, e.g. walking on uneven terrain or in unsupportive or too flexible shoes.
MCL sprain recovery time
Fortunately, the MCL has a really good blood supply, especially the superficial part, so it heals quite quickly for a ligament.
The recovery time for mild MCL sprains is about four to six weeks. Moderate to severe MCL injuries take about 12 weeks to fully rehabilitate.
However, like I explained earlier, an MCL injury sometimes goes hand-in-hand with an injury to the ACL and/or the meniscus. In these cases, the rehab time will be longer.
Another possible complication is bone bruising. This can happen if your injury was due to a sudden impact that also squashed the bottom end of the femur and the top end of the tibia together. Bruised bone takes longer to heal than ligaments – anything from two to four months.
So, you may still have pain in the inner part of your knee even though the MCL has healed. This is why it could be useful to get a scan if you're not recovering as expected, as it might explain why your pain is persisting for longer than expected.
Does an MCL tear require surgery?
No, the research shows that even Grade 3 MCL tears do really well with conservative management, i.e. the right combination of rest and protection (to allow the MCL to repair) and rehab exercises to strengthen the MCL and leg muscles that support it.
It is only in very specific cases that surgery may be required, like when the MCL has pulled away from the bone (avulsion fracture) and the muscles come between the two ends of the torn MCL.
We've made a short video about this:
Conservative treatment for MCL sprains
Type of treatment depends on the cause of the MCL sprain
The treatment approach for an MCL sprain should be informed by the cause and severity of your injury.
In the case of an overuse sprain, the focus will be as much on strengthening the body area that was the cause of the sprain (e.g. weak glutes) to prevent it from happening again as it will be on rehab for the MCL itself.
In the case of an acute MCL tear, on the other hand, the focus will be much more on protecting the knee and getting the MCL to heal. Issues such as hip stability would be secondary, because that is usually not what caused the injury.
Braces for MCL sprains
You may benefit from wearing a brace when you have an MCL sprain. Grade 1 sprains usually don’t require a brace, as long as you avoid activities that place strain on the MCL.
More serious Grade 2 and definitely Grade 3 tears require braces that limit the side-to-side movement of the knee but allows your knee to bend and straighten. We have a detailed article explaining what type of brace is best for MCL sprains, and when and for how long to wear them.
MCL sprain rehab exercises
A well-rounded rehab plan for an MCL sprain should include exercises that:
Restore the full range of motion in your knee.
Strengthen your core, glutes, and lower leg muscles – this improves the stability in your leg and reduces the strain on the MCL.
Challenge and develop your position sense and balance – these also improve your stability and control.
Strengthen the muscles that directly control your knee joint, e.g. quads and hamstrings.
The exercises should:
Never be forced into pain.
Start with stable, double-leg exercises (see examples below). They provide strength and help you develop good movement patterns in positions that don’t place much strain on the MCL.
Be progressed to single-leg exercises that challenge your balance but maintain stable, straight lines. These exercises increase the work on the MCL but not excessively.
Be progressed to include movements that challenge your knee in all directions and require more skill and control e.g. lunges into all directions.
Include sport-specific exercises during the later stage of rehab, e.g. hopping and jumping or changing direction, if that is required by your sport.
Slowly ease you back into your sport in the final stage of rehab. Your knee won’t yet have the full strength and endurance to cope with a full training session or competition; it’s important to build up to it over several weeks.
How quickly you can progress through these exercises will depend on the severity of your injury. Your physiotherapist will guide you and help you test when you’re ready to safely move on to the next stage.
Example of a range-of-motion exercise: Lying on your back and slowly bending and straightening you leg. Don't force it. Just go to where it feels comfortable.
Example of double-leg exercises: Squats and bridges
Examples of exercises that challenge your balance: Single leg balance, single leg squat, and single leg deadlifts.
Examples of exercises that challenge your knee in all directions: Balancing on unstable surface and lunges into all directions.
How do you know if your MCL is healed?
We usually consider an MCL as healed when a patient can perform the following activities without experiencing pain or swelling during or in the 24 hours after:
Move their knee fully into all directions
Someone can push on the outside of your knee, trying to gap the inner joint, without it hurting or making your joint move more than your uninjured one
Do exercises like lunges into all directions and at speed
Walk and run on uneven surfaces.
You should always gradually ease back into your sport to allow your MCL to regain its final level of strength. Your physio can help to guide you on this.
How we can help
Need more help with your injury? You’re welcome to consult one of the team at SIP online via video call for an assessment of your injury and a tailored treatment plan.
We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine. But at Sports Injury Physio we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.