Knee pain shows up in a lot of different spots, and the back of the knee is one of the more confusing ones to figure out on your own. It is a crowded area, tendons, a cushioning sac, blood vessels, and the back portion of the meniscus all sit close together, so pain there can come from more than one direction. We covered general knee pain causes in an earlier post, but pain specifically behind the knee deserves its own closer look.
What’s Back There, Anyway?
The back of the knee, known as the popliteal region, contains the hamstring tendons, the posterior horn of the meniscus, a fluid filled cushioning sac called a bursa, and the popliteal artery and vein, which are major blood vessels supplying the lower leg. Because there is a blood vessel involved, pain behind the knee is one of the few knee complaints where a circulation related cause always deserves consideration alongside the more common orthopedic ones.
Common Causes of Pain Behind the Knee
Baker’s cyst: This is one of the most frequent causes of pain and swelling behind the knee. According to Mayo Clinic, a Baker’s cyst forms when the knee produces excess joint fluid, often due to arthritis or a cartilage injury, and that fluid collects in a bursa at the back of the knee, creating a visible or palpable bulge along with stiffness and discomfort that tends to worsen with activity.
Meniscus tears: The meniscus has a posterior horn that sits toward the back of the joint, and according to Mayo Clinic, a tear here often causes pain, swelling, and a catching or locking sensation that can be felt more toward the back of the knee than the front or sides, especially with deep bending or twisting motions.
Hamstring tendinopathy: Overuse of the hamstring tendons, which attach near the back of the knee, can cause a persistent ache that builds gradually, often in runners, cyclists, or anyone who recently increased their activity level.
Muscle strain: A strained hamstring or calf muscle can refer pain to the back of the knee, particularly after a sudden, forceful movement during sports.
Osteoarthritis: General wear and tear in the knee joint can sometimes be felt more toward the back of the knee, especially when a Baker’s cyst develops as a secondary result of the arthritis itself.
When Pain Behind the Knee Could Be Circulation Related
This is the cause that is easy to overlook, and it is exactly why we wanted to write about this topic. A blood clot in the deep veins of the leg, called deep vein thrombosis or DVT, commonly causes pain, swelling, warmth, and redness in the calf, but it can also be felt behind the knee, since the popliteal vein runs directly through this area. According to Mayo Clinic, DVT can sometimes occur without obvious symptoms, which is part of why any new, unexplained swelling and pain in this area should not be dismissed as a simple muscle strain without at least considering it.
Less commonly, a popliteal artery aneurysm, a bulge in the artery wall behind the knee, can also cause pain or a pulsing sensation in this area. It is far less common than a Baker’s cyst or a meniscus issue, but because it involves the vascular system directly, it is exactly the kind of condition a vascular and interventional radiology team is well positioned to help evaluate.
Who Is More Likely to Develop a Blood Clot Behind the Knee
Certain factors raise the odds that new pain and swelling behind the knee is circulation related rather than orthopedic. Recent surgery, especially on the hip or knee, extended periods of sitting such as long flights or car rides, a history of previous blood clots, pregnancy, certain hormonal medications, smoking, and obesity all increase the risk of DVT. Age also plays a role, since the risk climbs steadily after age sixty. None of these factors mean a clot is definitely the cause of your symptoms, but if you fall into one of these categories, it is worth mentioning to whoever evaluates your knee pain so a vascular cause stays on the list.
How to Tell the Difference at Home
You cannot diagnose the exact cause of pain behind your knee without an exam and possibly imaging, but a few patterns can help you decide how quickly to get it checked out. Pain that came on gradually, worsens with bending or activity, and is accompanied by a visible bulge is more consistent with a Baker’s cyst or an orthopedic cause. Pain paired with new swelling, warmth, redness, or a feeling of tightness in the calf, especially if it appeared suddenly or you have recently been immobile for a long period, such as after surgery or a long flight, deserves prompt medical attention to rule out a blood clot.
When to Seek Care Right Away
Get evaluated quickly if you notice sudden swelling behind the knee or in the calf, skin that looks red or feels warm to the touch, pain that is worsening rather than improving, or any shortness of breath or chest pain along with leg symptoms, since that combination can signal a blood clot that has traveled to the lungs and requires emergency care.
How Doctors Diagnose the Cause
A physical exam usually starts with checking for swelling, tenderness, warmth, and range of motion in the knee. If a Baker’s cyst or meniscus tear is suspected, an ultrasound or MRI can confirm it and rule out other joint issues. If there is concern about a blood clot, an ultrasound of the leg veins is typically the first test used, since it is quick, painless, and highly effective at detecting DVT. Ruling out a vascular cause first is important, since the treatment approach for a blood clot is completely different from the approach for a cyst or tendon issue.
Treatment Options
Treatment depends entirely on the cause. A Baker’s cyst often improves once the underlying joint issue, such as arthritis, is treated, and the cyst itself can sometimes be drained if it is large or particularly uncomfortable. Meniscus tears and hamstring tendinopathy typically respond to rest, physical therapy, and activity modification, with surgery reserved for larger or persistent tears. If arthritis in the knee is driving ongoing pain, including pain that concentrates behind the joint, genicular artery embolization is a minimally invasive option we offer that targets the abnormal blood flow contributing to joint inflammation, often helping patients avoid or delay knee replacement surgery. For similar pain felt more toward the inside of the knee, our post on knee pain on the inside covers that presentation in more detail. If a blood clot is found, treatment usually involves blood thinning medication and close monitoring, and it should always be managed by a medical provider rather than at home.
Everyday Habits That Support Healthy Circulation and Joints
- Move regularly throughout the day, especially during long periods of sitting or travel
- Stay well hydrated, which supports healthy blood flow
- Stretch the hamstrings and calves regularly, particularly if you are active in sports that involve running or cycling
- Maintain a healthy weight to reduce pressure on the knee joint
- Wear compression stockings during long flights or car rides if you have risk factors for blood clots, such as a prior DVT or recent surgery
Frequently Asked Questions
Is a Baker’s cyst dangerous?
Usually not on its own, but a ruptured Baker’s cyst can cause symptoms that mimic a blood clot, including calf pain and swelling, so any sudden change should still be evaluated.
Can pain behind the knee go away on its own?
Mild cases related to overuse or a small Baker’s cyst sometimes improve with rest. Pain that is worsening, paired with swelling, or lasting more than a couple of weeks is worth having evaluated rather than waiting it out.
How do doctors rule out a blood clot versus a Baker’s cyst?
Both can cause swelling behind the knee or in the calf, so an ultrasound is typically used to look directly at the blood vessels and confirm or rule out a clot, since the two conditions require very different treatment.
Is pain behind the knee more serious than pain in the front of the knee?
Not necessarily, but because a major blood vessel runs through this region, providers tend to keep a vascular cause on the list of possibilities a little more readily than they would for pain in other parts of the knee.
If you are dealing with pain behind your knee, especially if it came with any swelling or warmth, it is worth getting it looked at rather than guessing. Contact our team so we can help figure out exactly what is going on and the best way to treat it.
