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There are many possible causes of pain in the back of the knee. Some are common and less serious, while others require more immediate medical attention.

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The knee is a complex joint, and it takes a lot of impact from even simple everyday activities. People can often reduce or prevent knee damage by avoiding impact and strain on the joint.

Treatment for pain in the back of the knee will vary greatly depending on the cause.

It is important to work closely with a doctor to diagnose pain in the back of the knee, as some causes require long-term treatment to heal completely.

Some possible causes of pain in the back of the knee include the following.

Leg cramps

Cramps occur when muscles become too tight. This tightness may be because the muscle is doing too much work without being stretched. If it is stretched and still cramps, the muscle may simply be overused.

Overuse syndrome can affect different areas of the knee. With this condition, a person might also feel a cramp in the thigh or calf near the knee.

The sensation resembles a sudden, painful spasm of the muscle. The pain may last for seconds or minutes and can range from uncomfortable to severe.

Some other possible reasons for leg cramp include:

  • dehydration
  • infections, such as tetanus
  • liver disease
  • excess toxins in the blood
  • nerve problems

Pregnant people may also experience leg cramps as a normal effect of pregnancy.

Some people who often experience leg cramps may find relief through regularly stretching their calves. Also, they can try shortening their stride to put less strain on the knee and surrounding muscles.

Baker’s cyst

A Baker’s cyst is a pocket of fluid that builds up in the back of the knee, leading to pain and swelling.

Baker’s cysts may not be noticeable at first, as small cysts do not typically cause pain. However, as the cyst grows, it may shift the surrounding muscles or put pressure on the tendons and nerves, causing pain.

Baker’s cysts may grow to about the size of a table tennis ball. People with Baker’s cysts often feel pressure in the back of the knee, which may cause a tingling sensation if the cyst is affecting a nerve.

In most cases, Baker’s cysts are not a cause for concern, but treatment can relieve the symptoms.

Osteoarthritis

Osteoarthritis is a condition that wears down the cartilage of the joints over time. This condition can easily cause pain in the back of the knee.

People with osteoarthritis in the knee may experience other symptoms, such as loss of motion or difficulty bending the knee. Inflammation in the joint may make it stiff and painful. A person may also feel this discomfort in other places around the knee.

Other forms of arthritis that could be causing the pain include autoimmune conditions such as lupus and rheumatoid arthritis.

Runner’s knee

Runner’s knee refers to the wearing down of the cartilage in the knee joint. When the cartilage is gone, the bones of the knee rub together. Typically, this causes a dull, aching pain behind the knee.

Some other symptoms of runner’s knee include:

  • the knee giving out or buckling randomly
  • weakness in the knee and leg
  • restricted movement in the leg and knee
  • a crackling or grinding feeling when the knee bends

Hamstring injury

A hamstring injury is a tear or strain in one or more of the muscles in the back of the thigh. These muscles include:

  • the biceps femoris
  • the semitendinosus
  • the semimembranosus

A hamstring strain happens if the muscle pulls too far. It may tear completely from being pulled too much, and this can take months to heal fully.

Hamstring injuries may be more common in athletes who run fast and in bursts, such as those who play basketball, tennis, or football.

Meniscus tears

The meniscus is a piece of cartilage on either side of the knee. Twisting motions while squatting or bending the leg may tear this cartilage. Many people hear a pop when they tear their meniscus.

The pain from a meniscus tear may not show up at first but typically worsens over the next couple of days.

Meniscus tears often cause other symptoms, including:

  • loss of knee motion
  • weakness and fatigue in the knee and leg
  • swelling around the knee
  • the knee giving out or locking up when used

Surgery may be necessary if a meniscus tear is severe and does not heal on its own.

Anterior cruciate ligament injuries

The anterior cruciate ligament (ACL) is a band of tissue that runs through the front of the knee joint, connecting the bones and helping keep the knee joint stable.

ACL strains often happen due to sudden stops or changes in direction. Similarly to meniscus tears, a strain in the ACL may cause a popping sound, followed by pain and swelling.

A torn ACL is a well-known, serious injury, often side-lining an athlete for a long time. Torn ACLs usually require reconstructive surgery.

Posterior cruciate ligament injuries

The posterior cruciate ligament (PCL) plays a similar role to the ACL, though it is less likely to become injured than the ACL.

PCL injuries may happen during traumatic events, such as falling directly onto the knee from a height or being in a vehicle accident. With enough force, the ligament may tear completely.

PCL injuries cause symptoms such as:

  • knee pain
  • stiffness in the knee if bending
  • difficulty walking
  • swelling in the knee

Completely resting the knee may help a PCL strain heal. However, a severe PCL injury may require surgery.

Deep vein thrombosis

A thrombosis is a blood clot, and a deep vein thrombosis (DVT) occurs when a clot happens in the veins deep within the leg.

Many people who have a DVT feel more pain when they stand up. However, some may feel pain in their leg and knee at most times.

Some other symptoms of DVT may include:

  • skin that is red or warm to the touch
  • swelling in the area
  • fatigue in the affected leg
  • prominently visible surface veins

Risk factors for DVT can include carrying excess weight, being older, and smoking. People who lead sedentary lives may also be likely to experience DVT.

DVT needs medication and care, as it can become more serious if the clot breaks loose into the bloodstream.

It is always a good idea to be sure that the muscles around the knee — especially the quads, calves, and hamstrings — are stretched properly. This may not protect against some of the traumatic causes of knee pain, but it could help the muscles respond better to activity.

Doctors often recommend the RICE treatment when an injury first occurs to help decrease pain and swelling. RICE stands for:

  • Resting (the leg)
  • Icing (the knee)
  • Compressing (the area with an elastic bandage)
  • Elevating (the injured leg)

In many cases, the RICE treatment may help reduce pain and swelling. However, Dr. Gabe Mirkin — who first coined the term in 1978 — has since stated that ice treatments can delay recovery from injury. People should consult a doctor or physical therapist about what treatment is right for them.

Taking nonsteroidal anti-inflammatory drugs (NSAIDs) is another way to ease pain and swelling while the knee is recovering. Some NSAIDs, such as ibuprofen, are available for purchase online.

In some cases, a doctor may recommend steroid injections to reduce symptoms.

With more serious injuries, doctors may use an MRI scan or a CT scan to obtain a complete image of the area. They might then suggest treatments that include physical therapy or surgery, depending on the severity.

Pain at the back of the knee may sometimes be a symptom of a serious issue. Anyone who is experiencing severe symptoms or symptoms that last for longer than a few days should contact a doctor.

Following a doctor’s treatment plan may give the injury the best chance to heal correctly and prevent any complications.