Bone bruising in the knee can be caused by a sudden trauma, such as twisting or a severe impact to the knee, or it can develop over time due to repetitive low impacts – for example in endurance running. Sports physio Maryke Louw explains what the best treatment is in both cases and gives some pointers on whether you can continue running with a bone bruise in your knee. 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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First, I should point out that this article is about bone bruises in the knee associated with activity, sport, or trauma; it's not about bone bruises associated with osteoarthritis or osteoporosis. Those types of bone bruise have different causes, and the advice in this article does not apply to them.
What is a bone bruise?
Bone bruising’s medical names are oedema, bone marrow oedema, and contusion of the bone.
It’s the same as a bruise you would get under your skin, except that it is in a part of a bone. So, there was an impact or several impacts on the bone, and now blood and other fluids have accumulated there. There may also be pain and swelling, same as with a bruise under the skin.
What causes bone bruises in the knee?
Trauma
The most common cause of bone bruising in the knee is obviously trauma. So, it's anything where you've had a sudden twist in or impact on the knee joint. The knee and ankle are the joints that typically suffer bone bruises this way.
In the knee, bone bruises typically go hand-in-hand with injuries to the anterior cruciate (ACL) ligament, which usually involve a sharp twist of the knee. Injuries to the medial collateral ligament (MCL) and to the meniscus often also cause bone bruises.
Repetitive low impact
However, you can also get a bone bruise to the knee without a once-off impact. This happens mostly due to activities that involve high-volume, low-intensity impact on the knee joints, such as running or dancing.
Marathon runners with bone bruising in their knees have been studied comprehensively. First, it should be noted that not everyone who trains for and runs marathons will get bone bruising in their knees. And interestingly, they found that, in some cases, bone bruising can actually get better during marathon training.
The people in the white lab coats speculate that this type of bone bruising develops in some cases because some people's running style cause a repetitive impact in a certain part of the knee. The terrain or shoes might also play a role, e.g. if you constantly run on a severe camber or in worn-out shoes.
Bone bruise symptoms and diagnosis
The only symptom is pain in the knee. But how do you know that this is pain caused by a bone bruise and not something else? The only sure-fire way to diagnose a bone bruise is by doing a scan, typically an MRI scan.
However, many people never know that they have or had bone bruising in the knee, because often there is no pain. In some research studies where they took scans of athletes’ knees before and after a season, many of them had developed bone bruises during the season but didn’t complain of pain or other symptoms.
Effect on recovery
When you have suffered a knee bone bruise due to trauma, such as injuring your ACL, the bone bruise may or may not affect how long it will take you to recover from the main injury.
In some ACL injury cases, pain from bone bruising can delay the patient’s being able to fully straighten their knee, which will influence how quickly the rehab of their ACL can progress.
The research suggests that bone bruising doesn’t seem to affect long-term ACL recovery or return to sport. So, when you look at the rehabbed ACL a few years down the line, it’s the same as a rehabbed ACL where there was no bone bruise.
However, if the cartilage that covers the bone around the bone bruise is also injured, it might affect your long-term recovery.
The scientists are not sure yet whether there is a specific volume or area of bone bruising that might have a bigger effect on recovery than others.
How to treat bone bruises in the knee
It’s quite simple (but admittedly not always easy): Keep active and move your knee as much as you want to but without aggravating your pain.
This is the basic approach for most joint injuries in any case, so it would slot in well with any rehab you might have to do for a main trauma knee injury such as an ACL or MCL tear at the same time.
1. Respect the pain
It is normal and expected to have some pain while you move and exercise with an injury. The aim is to stay as active as possible without making the injury worse, and pain can be a useful tool for monitoring this.
You wouldn't constantly be prodding a bruise on your arm and expect it to heal. So, firstly, don’t force any movements that cause the pain in your knee to increase significantly. Don't push into pain – respect it. If it hurts to extend your knee fully, work in the pain-free range and just move it gently.
And then, as the bone bruising heals, you can increase how far you move your knee.
The same goes for standing, walking, and running. Limit your weightbearing activities to what you can do with nothing more than mild discomfort. So, if it hurts to walk for 30 minutes, shorten your walks for the time being. Or if having to stand for lengthy periods at work is an issue, see if you can perch on a stool instead.
So, the realistic aim is to not increase the pain significantly rather than to be pain-free.
2. Keep moving your knee
The pursuit of not increasing your pain doesn’t mean that you should do nothing with your knee. Movement increases your circulation and is greatly beneficial for healing.
That's why it's important to do your rehab (in the case of a concurrent knee injury) and to do other activities as much as you can, as long as you respect the pain levels.
Healing time for knee bone bruises
Bone bruises are slow healers, and they usually take a few months to resolve. Healing times vary too much from person to person to provide more specific timelines; it depends on factors such as the severity and how it was caused.
Can I run with a bone bruise in my knee?
The research provides no clear answers here, and expert opinion is divided. Some clinicians advise that you avoid impact sports until the bruise has recovered, while others recommend tailoring your activities to the symptoms.
Like I mentioned above, there are researched cases of marathon runners whose knee bone bruising actually got better during marathon training. Others picked up bone bruises in the knee during training; some of those had healed six months later (while still training) and others hadn’t.
In some cases, it might be that it’s not whether you run, but how and where you run. As mentioned earlier, bone bruising in the knee might be caused by your running style or the terrain you run on, so this might also influence how fast your bone bruising heals if you continue running with it. Your type of running shoes might also be a factor.
From what I've read, I recommend that you use your common sense and let your symptoms guide you. If running does increase your knee pain (and there’s no other injury to blame for it), I would stay away from it for a while (or ease up so there’s no increased pain) and rather choose lower-impact activities such as cycling or swimming.
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 or at least 10 years' experience in the field. 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.
About the Author
Maryke Louw is a chartered physiotherapist with more than 20 years' experience and a Master’s Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.