Why Do I Have Pain Behind Knee Joint? Causes and Treatments

Any kind of leg pain is enough to make your day difficult. Whether standing, walking, turning, or sometimes even sitting, pain in the leg muscles and joints can make it hard to do your normal activities.

Pain behind knee joints can be especially debilitating. Your knee bends and straightens with every step. If something isn’t right with the joint, you’ll know it! It’s in your best interest to identify and treat behind-knee pain as soon as possible to prevent damage!

Let’s look at the anatomy of the knee and some conditions that can cause pain in knee joints.

The Anatomy of the Knee

Your knee is the largest and most complex hinge joint in the body. It’s supported by a network of connecting muscles, tendons, and ligaments. These all work together to allow the knee to move while providing stability as well.

Numerous synovial-filled sacs throughout the knee, known as bursa, help the knee to move smoothly. You also have cartilage—the medial and lateral menisci—that attaches in the back of the knee and acts as a shock absorber between the femur and tibia.

There’s also a series of nerves, veins, and an artery—popliteal—in the back of the knee that supply blood and oxygen to your lower leg and foot.

Due to the complex structure of the knee, the cause of your pain behind the knee can have a variety of causes.

What Can Cause Pain Behind the Knee?

Pain behind the knee—also known as posterior knee pain—can be tricky to diagnose due to the complexity of the joint. But there are telltale signs of various conditions to look out for.

Here are some of the most common reasons for pain behind the knee.

PCL Injury

The posterior cruciate ligament, or PCL, is a strong ligament in the knee that connects your femur—thigh bone—to your tibia—shin bone. Although it’s similar to the anterior cruciate ligament—ACL—the PCL ligament is bigger and stronger.

The PCL ligament works alongside the other ligaments in your knee to prevent your thigh and shin bones from moving out of place and to control your knee’s forward and backward motion.


The most common cause of a PCL injury is a direct blow to the knee while it’s bent. This can occur if you fall and land on your bent knee or if you’re involved in a car accident where your knees hit the dashboard.

You can also injure your PCL ligament if your knee overextends, either in a sudden movement or if you land awkwardly after jumping.


The symptoms of PCL injury can vary from mild to severe, depending on the extent of the injury. In some cases, you may not experience any symptoms at first after the initial injury.

However, in most cases, when you’ve injured your posterior cruciate ligament, you’ll experience pain in the knee joint, behind the knee, especially when you bend it. The back of the knee will be tender to the touch, and there will be mild to severe swelling.

It may feel as though your knee is unstable or that it will “give out”. You may find walking difficult, or the pain causes you to limp.


Treatment for a PCL injury will depend on the severity of the injury and whether any other muscles, ligaments, or tendons are also injured.

The best way to start treatment is to follow the PRICE principle:

  • Protect the knee from further injury by supporting it using a brace or splint
  • Rest your knee as much as you can
  • Ice the knee with the cold compress for 10 to 20 minutes every 2 to 4 hours
  • Compress the injured area with an elastic bandage
  • Elevate the knee above the level of your heart

Your doctor may recommend wearing a special knee brace to prevent your tibia bone from being pulled backward. Over-the-counter painkillers like ibuprofen or naproxen can help reduce swelling and pain.

Once the swelling has gone and you can put weight on your injured leg again, you can go for physical therapy. This will help to strengthen the leg muscle and ensure that you restore full function to your knee.

Your doctor may recommend surgery if:

  • The ligament or soft tissue in your knee has been torn or severely damaged
  • Your knee remains painful or feels unstable even with physical therapy

A Popliteal Cyst

A popliteal cyst, also known as a Baker’s cyst, is a fluid-filled sac—popliteal bursa—that develops inside a thin layer of tissue at the back of your knee.

At first, the cyst may not be noticeable and won’t cause any pain. But as fluid continues to build up, the cyst will get bigger and, in some cases, can get as large as a baseball.

The bulge of the cyst causes the surrounding soft tissue to shift, placing pressure on the tendons and the nerves in the back of the knee. This pressure can cause pain or a tingling sensation in the back of the knee.


A popliteal cyst is caused by inflammation. This could be due to an injury or an underlying condition that causes the knee to produce too much synovial fluid, leading to fluid accumulation in the popliteal bursa.

Some common conditions that can lead to a popliteal cyst developing are:

  • Arthritis—osteoarthritis and rheumatoid
  • Gout
  • Meniscus tear
  • An anterior cruciate ligament (ACL) tear


In the early stages, a popliteal cyst may not cause you any discomfort. You may not even know it’s there! But as the fluid continues to accumulate and the lump increases in size, you may experience pain in and behind your knee.

There will also be swelling behind your knee that can extend into your lower leg, and you may feel stiffness or tightness at the back of the knee. This can also make flexing your knee difficult and painful.

It’s important to seek medical treatment when the cyst becomes bigger, as it can place pressure on the surrounding veins, which can interfere with the blood flow of your leg. This can lead to you experiencing numbness and weakness alongside the pain and swelling.

Popliteal cysts can rupture. When this happens, you may feel a sharp pain in your knee along with weakness in the joint.


A popliteal cyst will sometimes go away without any treatment. However, it’s best to seek the advice of a doctor, as in some cases, the cyst can rupture or cut off blood flow.

Your doctor may recommend an ultrasound if the cyst is still small. It may require observation until it goes away on its own or grows.

If it’s large and obvious, the doctor may treat it with steroid injections or drain the cyst. You may also need to modify your activities—from high-impact to low-impact—to ensure that you don’t aggravate the knee.

It’s important to consider any potential underlying condition that may have caused the cyst. Rather than simply treating the symptoms, it’s important to treat the root cause to prevent the cyst from recurring.


Arthritis is a common cause of knee pain in people over 50, although it can also affect younger people.

Although there are over 100 different types of arthritis, the two most common types are osteoarthritis—wear and tear—and rheumatoid arthritis—an inflammatory autoimmune condition.

Both of these can lead to pain behind the knee. If you have osteoarthritis, the cartilage between the femur bone and the tibia begins to wear away, leaving the two bones to rub together. This causes inflammation of the surrounding tissues.

Rheumatoid arthritis is an autoimmune disease in which the body mistakenly attacks its own tissues. This causes pain in the joints throughout the body as the synovium—joint lining—is affected, and may include the knee joint.


Osteoarthritis is often caused by wear and tear as you age or after an injury in which the joint has been compromised.

The wear and tear on lower body joints can be accelerated if you’re overweight, have a job that includes manual labor, or do high-intensity exercise often, such as running.

It’s still unclear why rheumatoid arthritis develops. There may be a genetic risk. Arthritis is also more common in women than in men.


If you have arthritis in your knee, you will feel pain when you bear weight on the knee. The pain often increases when you’re active and eases when you rest the joint.

There may be stiffness in the knee when you move again after resting. You may also have swelling in the knee, or it could sometimes lock in position, creak or grind, or give way as you’re walking.

With osteoarthritis, there’s a chance that only one joint is affected, depending on the reason behind it. With rheumatoid arthritis, it’s likely that more joints than just the one will be painful.


Although there is no cure for arthritis, there are various steps you can take to improve your symptoms and protect your joints.

You should maintain a healthy weight to reduce pressure on the joints. Wearing well-cushioned shoes can also help to lower the amount of shock on your knee, and you should also make sure your shoes support your foot properly.

Light, low-impact exercise can strengthen the muscles around the painful joint and alleviate pain.

To manage the pain of arthritis on a daily basis, you can use a heat pack or an ice pack for 10 to 20 minutes, 3 to 4 times a day.

Over-the-counter NSAIDS like ibuprofen can also be helpful in reducing inflammation and pain in the joints.

Your doctor may suggest a steroid injection into the joint to relieve inflammation and pain. Alternatively, physiotherapy may help to lower pain and improve your range of movement.

Hamstring Injury

The hamstring is a set of three muscles—semitendinosus, semimembranosus, and biceps femoris—that run down the back of your thigh, above the knee. They help you to bend and straighten your knee as you walk or run.

If the biceps femoris muscle is injured, it can lead to pain behind the knee as the biceps femoris muscle connects behind the knee. Every step you take can cause extra strain, making the pain worse.


This kind of injury usually occurs when the muscle is stretched too far. In severe cases, the muscle can tear, but in most cases, it simply pulls.

Hamstring injuries are common in athletes who run or take part in sports with sudden movements or direction changes. Sprinters, runners, tennis players, soccer players, and basketball players are prone to hamstring injuries.


When the injury occurs, you’ll feel sharp pain either in the thigh, behind the knee, or in both areas. You may also notice swelling, bruising, and weakness in your hamstrings.

The pain in the thigh or behind the knee may increase when you bend your knee.


The best course of treatment for hamstring injuries is to rest the muscle. You should try to stay off your feet and avoid activity for a few days. Once you’ve rested for a few days, you can start doing gentle strengthening exercises.

You should stretch your hamstrings regularly to prevent this from happening again by keeping your muscles supple and flexible.

Sprained Ligament

The ligaments in the knee maintain the stability of the joint. They’re thick bands of fibrous tissue that connect bone to bone.

There are four important ligaments in the knee:

  • PCL—posterior cruciate ligament, connects the femur to the tibia at the back
  • ACL—anterior cruciate ligament, connects the femur to the tibia at the front
  • MCL—medial collateral ligament, connects the femur to the tibia on the outside of the knee
  • LCL—lateral collateral ligament, connects the femur to the fibula on the outside of the knee

When thy overstretch or tear, this is considered to be a sprained ligament. Pain behind the knee is often caused by the PCL becoming sprained, but it can also happen with other ligament sprains.


Ligament sprains usually happen by a sudden twisting motion to the knee. This could be as a result of a blow to the knee or by pivoting quickly during movement.


You may hear a loud pop or snap when the injury occurs, followed by sudden and severe pain in the knee. Your knee may swell up severely within the first 24 hours after the injury, and there may also be some bruising.

When the swelling subsides, your joint may also feel loose and unstable. You may not be able to place weight on the joint due to the instability, even if the pain isn’t too bad.


The best course of treatment is to rest your leg and wear a knee brace to help support the injured knee. You can ice your knee for 10 to 15 minutes at a time, 3 to 4 times a day, to relieve the pain.

Over-the-counter anti-inflammatory medication can help to reduce swelling and redness, as well as manage the pain.

In most cases, mild to moderate sprains will not require surgery. In cases where the ligament has snapped, your doctor may do reconstructive knee surgery.

Less Likely Causes

There could be many other causes behind knee pain, although those are the most common. However, two less common reasons that are worth mentioning include meniscus tears and DVT—deep vein thrombosis.

Meniscus Tear

The meniscus is a piece of cartilage in the knee that absorbs shock. It can be torn when your knee gets twisted suddenly. This is common in football, squash, and other sports with sudden direction changes.

You may hear a popping sound and experience pain as the injury occurs. It may also lead to the knee becoming locked, as a piece of the cartilage gets stuck in the joint.

As most of the meniscus has a poor blood supply, this may need surgery if the tear is severe enough. However, you can first try conservative treatments like RICE, NSAIDS, stretching and strengthening exercises, and resting from activity.

Deep Vein Thrombosis

DVT is when a blood clot forms deep inside the leg. This is a dangerous condition, as the blood clot can travel through the bloodstream to the lungs or heart, where it can cause cardiac arrest or a pulmonary embolism.

You’ll feel a pain deep inside the leg, especially when standing up from seated. There may also be swelling in the leg, redness, and unusual warmth. In advanced cases, you may experience leg ulcers.

Deep vein thrombosis could be caused by injury to the blood vessels or as a result of a condition affecting the way your blood clots.

You should see a doctor if you suspect that you may have DVT. It’s treated with blood thinners in the early stages, and the blood clot should break down on its own.

In more severe cases or with larger clots, the doctor will give you thrombolytics, which help to break the clot up faster.

Tips to Avoid Knee Injuries

Strengthening your knees can help to reduce the chance of developing a knee injury. Here’s what you can do to lower your chance of injury.

Strengthen the Supporting Muscles

Strengthening your quadriceps, hamstrings, and calf muscles will help the knee stay safer. When these muscles are strong, they hold the joint in place and make it less prone to being jarred out of place.

You should include leg-strengthening exercises in your weekly routine. Just 2 days a week of leg exercises will help to strengthen these muscles and protect your knee joints better.

  • Leg extensions
  • Squats (check your form)
  • Hamstring curls
  • Calf raises
  • Deadlifts (regular & Romanian)

Wear the Right Shoes

Choosing your shoes for knee pain carefully will help soften the shock’s impact on your feet and knees. This isn’t just a consideration for those who play sports—your feet need to be supported and cushioned no matter what you’re doing.

If you overpronate—roll your feet inwards—you need a stability shoe. You should also make sure there’s enough cushion in the midsole of the shoe to absorb shock as you walk or run and a thick rubber outsole to keep you safe from slips that could jar the knee.

Play Sports Carefully

Many types of knee pain are caused by injury during sports, so it’s worthwhile to ensure your form is correct whenever you do any sports.

Whether you’re a runner, a tennis player, or you enjoy walking, you should ensure that you’re doing it correctly to ensure that your joints stay aligned.

Ask a coach to help you correct any form problems you may have.

When Should You See a Doctor About Pain Behind the Knee

While most of these causes of pain behind knee joints can be treated at home, there are certain cases in which you should see a doctor.

  • Severe, unbearable pain that doesn’t ease with rest and medication
  • Severe swelling or bruising
  • Deformity of the knee joint
  • Symptoms that extend past the knee
  • If you don’t improve with conservative treatment
  • If you have underlying conditions that could interfere with healing
  • Signs of an infection, like a fever

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