Pain behind the knee can make everyday movement uncomfortable. Walking, bending the leg, climbing stairs, or fully straightening the knee may all become difficult.
The cause is not always inside the knee joint itself. Pain may come from the muscles, tendons, cartilage, ligaments, nerves, or blood vessels around the area.
Other symptoms can offer important clues. Swelling, stiffness, instability, calf pain, numbness, or a lump behind the knee may point toward different causes.
Sudden pain accompanied by significant swelling, warmth, or calf tenderness should be evaluated promptly because circulation problems can sometimes cause similar symptoms.
People dealing with ongoing knee pain can explore personalized pain management in New Jersey at The Center for Regenerative Therapy and Pain Management.
Quick Answer: Why Does the Back of My Knee Hurt?
Pain behind the knee may be caused by:
- A Baker’s cyst
- Arthritis
- A muscle or tendon strain
- A meniscus injury
- A ligament injury
- Nerve irritation
- A blood clot
The location of the pain alone cannot confirm the cause. Doctors also consider when the pain began, what activities make it worse, whether there is swelling, and whether the knee locks, gives out, or feels numb.
Common Causes of Pain Behind the Knee
Baker’s Cyst
A Baker’s cyst is a fluid-filled swelling that develops behind the knee.
It often forms when another knee problem causes the joint to produce excess fluid. Arthritis and meniscus injuries are common underlying causes.
Symptoms may include:
- A lump or feeling of fullness behind the knee
- Tightness
- Pain when bending or straightening the leg
- Swelling that extends into the calf
A Baker’s cyst can sometimes rupture and cause pain, swelling, or bruising behind the knee and into the calf. These symptoms can resemble a blood clot, so prompt evaluation is important.
Arthritis
Arthritis can cause inflammation, stiffness, and excess fluid inside the knee joint.
Osteoarthritis may lead to:
- Aching
- Stiffness
- Swelling
- Reduced range of motion
- Pain during or after activity
The buildup of extra joint fluid may also contribute to the formation of a Baker’s cyst behind the knee.
Hamstring or Calf Strain
Several muscles and tendons cross the back of the knee. These tissues may become strained after sudden movement, overuse, or overstretching.
Common triggers include:
- Running
- Jumping
- Sudden acceleration
- Heavy lifting
- Overstretching
Pain may worsen when bending the knee, walking, pushing off the foot, or stretching the affected muscle.
Tendon Irritation
Tendons from the hamstring, calf, and popliteus muscles help control movement around the back of the knee.
Repeated strain or overuse can irritate these tendons.
Possible symptoms include:
- Localized tenderness
- Pain with repeated movement
- Stiffness after activity
- Discomfort when fully bending or straightening the knee
Tendon pain often develops gradually rather than after one obvious injury.
Meniscus Injury
The meniscus is a piece of cartilage that helps cushion and stabilize the knee.
A meniscus tear may develop after a sudden twisting movement or gradually through age-related wear.
Symptoms may include:
- Pain toward the back or side of the knee
- Swelling
- Catching
- Locking
- Difficulty fully straightening the knee
Meniscus injuries commonly produce swelling, instability, or locking and catching sensations. They may also increase joint fluid and contribute to Baker’s cyst formation.
Ligament Injury
Ligaments help keep the knee stable.
An injury may occur after:
- A sudden twist
- A fall
- A collision
- An awkward landing
- A forceful change in direction
Possible symptoms include immediate pain, swelling, instability, or a popping sensation at the time of injury.
The location and severity of symptoms depend on which ligament is affected.
Nerve-Related Pain
Pain behind the knee does not always begin in the knee.
A compressed or irritated nerve in the lower back, pelvis, or leg may cause pain that travels into the back of the knee.
Nerve-related symptoms may include:
- Burning
- Tingling
- Numbness
- Electric or shooting pain
- Pain extending into the calf or foot
Sciatica is one example of a nerve problem that may cause radiating pain through the back of the thigh, knee, calf, or foot.
Deep Vein Thrombosis
Deep vein thrombosis, or DVT, occurs when a blood clot forms in a deep vein.
A clot in the leg may cause:
- Pain behind the knee or in the calf
- Swelling
- Warmth
- Tenderness
- Red or discolored skin
DVT requires urgent medical evaluation because a clot can potentially travel to the lungs.
A Baker’s cyst and DVT may cause similar pain and swelling. It is not always possible to safely tell them apart based on symptoms alone.
What Symptoms May Point to the Cause?
The way the pain feels and the symptoms around it may help narrow down the possible cause.
Pain With a Lump or Fullness
A lump, pressure, or feeling of fullness behind the knee may suggest a Baker’s cyst.
The swelling may feel more noticeable when standing or fully straightening the leg.
Pain After Exercise or Injury
Pain that begins after exercise, twisting, impact, or a sudden increase in activity may involve a:
- Muscle
- Tendon
- Meniscus
- Ligament
Think about whether the pain began during a specific movement or developed gradually after repeated activity.
Pain With Locking or Catching
A knee that locks, catches, or becomes difficult to straighten may have a meniscus injury or another mechanical joint problem.
These symptoms are more concerning when they occur with swelling or instability.
Pain With Numbness or Tingling
Burning, numbness, tingling, or electric pain may point toward nerve irritation rather than an isolated knee-joint problem.
The pain may also travel from the lower back or thigh into the calf or foot.
Pain With Calf Swelling
Pain behind the knee with calf swelling may result from a ruptured Baker’s cyst or a blood clot.
Both can cause pain, swelling, and tenderness. Rather than trying to distinguish between them at home, seek prompt medical evaluation.
How Is Pain Behind the Knee Diagnosed?
Pain behind the knee can come from several different structures, so diagnosis usually begins with the pattern of symptoms rather than the location alone.
A doctor may look at how the pain started, what movements make it worse, and whether swelling, weakness, locking, or nerve symptoms are present.
Medical History
The medical history helps narrow down the most likely cause.
A doctor may ask about:
- When the pain began
- Whether there was a fall, twist, impact, or other injury
- Which activities make the pain worse
- Where swelling occurs
- Whether the knee locks, catches, or feels unstable
- Whether there is numbness or tingling
- Personal risk factors for blood clots
Blood clot risk factors may include recent surgery, prolonged immobility, certain medical conditions, or a previous history of clots.
Physical Examination
During the physical examination, the doctor may check:
- Swelling
- Tenderness
- Range of motion
- Muscle strength
- Knee stability
- Walking pattern
- Circulation
- Sensation
The knee may also be gently bent, straightened, or rotated to see which movements reproduce the pain.
Imaging and Testing
Testing depends on the symptoms and the likely cause.
Possible tests include:
- X-rays: May show arthritis, joint-space narrowing, or other bone changes.
- Ultrasound: May help identify a Baker’s cyst or evaluate blood flow when a clot is suspected.
- MRI: May show the meniscus, ligaments, tendons, cartilage, and other soft tissues.
- Blood clot testing: May be ordered when symptoms suggest deep vein thrombosis.
Not every patient needs every test. The evaluation should be based on the symptoms, examination findings, and level of concern.
How is Pain Behind the Knee Treated?
Treatment depends on what is causing the pain.
A muscle strain, arthritis flare, Baker’s cyst, nerve problem, and blood clot all require different approaches. That is why identifying the source is important before beginning treatment.
Rest and Activity Changes
Temporarily reducing activities that worsen the pain may give irritated tissues time to recover.
This may include avoiding:
- Deep knee bending
- Heavy lifting
- Running or jumping
- High-impact exercise
- Repeated twisting
Complete inactivity is not always helpful. When safe movement is possible, gentle activity may reduce stiffness and help maintain strength.
Physical Therapy
Physical therapy may help restore movement and improve support around the knee.
A treatment plan may focus on:
- Strengthening the muscles around the knee
- Improving flexibility
- Restoring range of motion
- Correcting movement patterns
- Improving balance and stability
The exercises should match the condition. A patient recovering from a strain may need a different program than someone managing arthritis or nerve-related pain.
Medication Management
Medication may help control pain or inflammation.
The right approach depends on the patient’s health, symptoms, current medications, and the underlying condition.
Medication should be used under appropriate medical guidance, especially for patients with other health conditions or those taking multiple prescriptions.
Targeted Injections
Targeted injections may be considered when arthritis or another inflammatory joint condition is contributing to the pain.
The type and location of the injection depend on the identified pain source.
Injections are not appropriate for every cause of pain behind the knee. They would not be used to treat problems such as a blood clot, and they may not be the right choice for every injury.
Treating the Underlying Condition
Long-term improvement often depends on treating the actual cause.
This may involve:
- Managing arthritis
- Treating a meniscus or ligament injury
- Addressing nerve irritation
- Managing a Baker’s cyst
- Treating a muscle or tendon injury
- Providing emergency care for a blood clot
A Baker’s cyst, for example, may improve when the underlying knee inflammation is properly managed.
When Should You See a Doctor?
Pain behind the knee should be evaluated when it does not improve or begins affecting normal movement.
Consider seeing a doctor when the pain:
- Lasts more than several days
- Keeps returning
- Causes swelling or stiffness
- Limits walking
- Prevents the knee from fully bending or straightening
- Causes locking or instability
- Develops after a significant injury
- Is accompanied by numbness or weakness
A medical evaluation is also important when the cause is unclear or basic care is not helping.
When is Pain Behind the Knee an Emergency?
Some symptoms require urgent medical attention.
Seek immediate care for:
- Sudden calf or leg swelling
- Warmth or redness
- Severe unexplained pain
- Shortness of breath
- Chest pain
- Inability to place weight on the leg
- A visibly deformed knee
- Sudden weakness or loss of sensation
Chest pain or difficulty breathing alongside leg swelling may indicate that a blood clot has traveled to the lungs. This is a medical emergency.
Sudden weakness, numbness, or loss of movement may also indicate a serious nerve or circulation problem.
Frequently Asked Questions About What Causes Pain Behind the Knee
Can Arthritis Cause Pain Behind the Knee?
Yes. Arthritis can cause inflammation, stiffness, and excess fluid inside the knee joint.
This may create pain or pressure behind the knee and may also contribute to the formation of a Baker’s cyst.
What Does a Baker’s Cyst Feel Like?
A Baker’s cyst may feel like a soft lump, pressure, fullness, or tightness behind the knee.
The sensation may become more noticeable when standing or fully straightening the leg.
Can a Pulled Muscle Cause Pain Behind the Knee?
Yes. A strain involving the hamstring, calf, or nearby tendons may cause pain behind the knee.
The pain may worsen when bending the leg, walking, running, or pushing off the foot.
Can Sciatica Cause Pain Behind the Knee?
Yes. Sciatic nerve irritation can cause pain that travels through the buttock, thigh, back of the knee, calf, or foot.
Nerve-related pain may feel burning, electric, sharp, numb, or tingly.
Should I Be Worried About Pain Behind the Knee?
Mild pain after activity may improve with rest and basic care.
Sudden pain, significant swelling, calf warmth, skin discoloration, chest pain, or difficulty breathing requires urgent medical evaluation.
Can a Pain Management Doctor Help?
A pain management doctor can evaluate persistent knee pain and help determine whether it is coming from the joint, surrounding tissues, or nearby nerves.
Depending on the cause, treatment may include:
- Activity guidance
- Physical therapy
- Medication management
- Targeted injections
- Treatment for nerve-related pain
The right plan should be based on the actual source of the symptoms.
Conclusion
Pain behind the knee may come from a Baker’s cyst, arthritis, a muscle or tendon injury, a meniscus problem, nerve irritation, or a circulation issue.
Because these conditions can cause similar symptoms, treatment depends on identifying the actual source of the pain.
Evaluation is especially important when symptoms persist, limit movement, cause swelling, or affect the ability to walk.
Contact The Center for Regenerative Therapy and Pain Management to discuss personalized pain treatments in New Jersey for ongoing knee pain.
