Back of knee pain can come from several different structures packed into a relatively small area. Muscles and tendons from the thigh and calf cross behind the knee, important ligaments stabilize the joint, cartilage sits inside it, and blood vessels and nerves pass through the same region.
That means pain behind the knee can feel similar even when the causes are very different.
A tight ache after exercise might come from a hamstring or calf strain. Pain with catching or locking can suggest a meniscus problem. A soft lump or pressure sensation may be a Baker’s cyst. Pain and stiffness after sitting can occur with knee arthritis. And sudden calf swelling, warmth, or discoloration requires a very different level of attention because a blood clot needs to be considered.
At Mount Prospect Health Centre in Newark, NJ, persistent knee symptoms are evaluated according to how the pain began, where it is located, which movements trigger it, whether swelling or instability is present, and how the problem affects walking and daily activity.
What Is Back of Knee Pain?
Healthcare professionals sometimes call pain in this area posterior knee pain.
The posterior knee is the region between the lower hamstring muscles and upper calf where your knee creases when you bend your leg. Pain here may feel aching, tight, sharp, pinching, burning, or like pressure behind the joint. Some people notice a visible or palpable lump.
The symptom pattern can provide useful clues.
| Symptom Pattern | Possible Causes to Consider |
| Pain after sprinting, lifting or sudden acceleration | Hamstring or calf muscle/tendon injury |
| Pain or pressure with a lump behind the knee | Baker’s cyst |
| Pain when bending or twisting with catching/locking | Meniscus injury |
| Pain after dashboard impact or force to a bent knee | PCL injury |
| Stiffness after sitting that eases somewhat with movement | Osteoarthritis |
| Pain with running, especially downhill | Posterior tendon/popliteus irritation |
| Pain with swelling, warmth or redness in one calf | DVT must be ruled out |
| Posterior pain without clear knee findings plus back/hip symptoms | Referred pain may be possible |
No single symptom confirms a diagnosis. The pattern simply helps determine which structures deserve closer examination.
1. Hamstring Strain or Hamstring Tendon Pain Behind the Knee
Your hamstrings run along the back of your thigh and cross toward the knee through several tendons.
A sudden sprint, acceleration, slip, forceful stretch, heavy exercise session, or repetitive loading can injure these muscles or irritate their tendons.
Hamstring tendon pain behind the knee may feel like:
Pain toward the inner or outer back portion of the knee, tenderness along the tendon, tightness through the back of the thigh, pain when bending the knee against resistance, or discomfort while walking quickly or running.
An acute hamstring strain is more likely to begin suddenly during activity. Tendinopathy more often develops gradually after repeated loading.
A sports-medicine review of posterior knee pain identifies hamstring injuries and tendinopathy among important musculotendinous causes.
2. Calf or Gastrocnemius Strain
The gastrocnemius—the large superficial calf muscle—crosses the knee joint before continuing into the Achilles tendon.
That means an upper-calf injury can be felt close enough to the knee that it seems as though the pain is coming directly from behind the joint.
A calf strain may occur during:
Running, jumping, pushing forcefully off the ground, sudden changes in direction, or overstretching the leg.
The discomfort often increases when pushing through the foot, climbing stairs, walking quickly, or stretching the calf.
Cleveland Clinic and INTEGRIS both include calf or leg muscle injuries among musculoskeletal explanations for posterior knee symptoms.
However, new calf pain combined with significant swelling, warmth, or skin-color change should not automatically be diagnosed as a muscle strain, because similar symptoms can occur with deep vein thrombosis.
3. Baker’s Cyst
A Baker’s cyst, also called a popliteal cyst, is one of the best-known causes of pain or fullness behind the knee.
It is a fluid-filled swelling that develops when excess synovial fluid from the knee joint collects toward the back of the knee.
Baker’s cysts are commonly associated with another knee problem, such as:
Osteoarthritis, rheumatoid arthritis, meniscus injury, or other conditions that increase joint inflammation and fluid production.
What Does Baker’s Cyst Knee Pain Feel Like?
Some Baker’s cysts cause no symptoms.
When symptoms are present, you may notice a soft lump, pressure behind the knee, tightness, aching, stiffness, or difficulty completely bending or straightening the knee.
Symptoms can become more noticeable after prolonged standing, walking, or activity.
Why Does a Baker’s Cyst Hurt When Straightening the Knee?
A larger cyst occupies space behind the joint.
As the knee reaches full extension or deep flexion, surrounding tissues can become compressed or tensioned, creating a feeling of tightness or pain.
That is why a Baker’s cyst can contribute to knee pain when straightening the leg as well as difficulty fully bending it.
Can a Baker’s Cyst Burst?
Yes.
A ruptured Baker’s cyst can allow fluid to move down into the calf, producing sudden pain, swelling, warmth, bruising, or discoloration.
The important problem is that those symptoms can resemble a blood clot. NHS and MedlinePlus specifically advise medical evaluation because a ruptured cyst and DVT can be difficult to distinguish based on symptoms alone.
4. Meniscus Tear
Each knee contains two menisci—crescent-shaped pieces of cartilage that help distribute force between the thighbone and shinbone.
A meniscus can tear after a twisting injury, a pivot during sports, a fall, or gradually through degenerative changes.
Depending on the location of the tear, symptoms can be felt toward the back of the knee.
Clues may include:
Pain when bending deeply, pain during twisting or pivoting, swelling, a clicking sensation, catching, or a feeling that the knee is locking.
Bupa specifically notes that meniscal injuries can cause posterior knee pain during bending or twisting. AAOS notes that meniscal tears commonly cause pain, swelling and limited movement and that mechanical symptoms can be important in treatment decisions.
What Does a Locked Knee Mean?
A true locked knee means you physically cannot completely straighten or bend the joint—not simply that it hurts to do so.
A displaced meniscal tear is one possible cause.
Persistent locking deserves evaluation because mechanical blockage inside the joint may require different treatment than uncomplicated muscle soreness.
5. Posterior Cruciate Ligament Injury
The posterior cruciate ligament, or PCL, sits deep inside the knee and helps prevent the shinbone from moving too far backward relative to the thighbone.
A classic PCL injury can occur when the front of a bent knee receives a strong blow.
One common example is a knee striking the dashboard during a motor vehicle collision. Contact sports and falls onto a bent knee can also injure the PCL.
Possible symptoms include posterior knee pain, swelling, difficulty walking, instability, or discomfort when descending stairs or walking downhill.
PCL injuries may occur together with damage to other knee structures, so traumatic posterior knee pain deserves a more complete ligament examination.
6. Knee Osteoarthritis
Osteoarthritis can cause pain throughout the knee, including the posterior region.
It develops as cartilage and other joint structures change over time and becomes more common with increasing age.
Typical symptoms can include:
Aching with weight-bearing, reduced mobility, swelling, stiffness, and discomfort after the knee has remained still.
Why Does My Knee Hurt After Sitting?
Knee pain after sitting can occur with osteoarthritis because the joint may stiffen during periods of rest.
A person may feel particularly stiff when getting out of a chair, standing after driving, or taking the first few steps after sitting for an extended period.
The stiffness may ease somewhat after moving around.
Bupa describes this “stiff after rest, easier after moving” pattern in knee osteoarthritis.
However, pain after sitting is not specific enough to diagnose arthritis by itself.
7. Popliteus and Other Posterior Tendon Overuse
A small muscle called the popliteus lies deep at the back of the knee and helps control rotation of the lower leg during movement.
It is much less familiar than the hamstrings, but it can contribute to posterolateral knee pain—pain toward the outer back portion of the joint.
Popliteus problems can occur after trauma or repetitive stress. Running downhill may be particularly provocative in some cases.
Sports-medicine literature identifies three important muscle-tendon groups around the posterior knee:
The hamstrings, gastrocnemius and popliteus.
Because popliteus symptoms overlap with meniscus, ligament and other posterior knee problems, it is difficult to confidently self-diagnose.
8. Inflammatory Arthritis or Other Joint Inflammation
Not every case of posterior knee pain is caused by wear-and-tear arthritis.
Inflammatory conditions such as rheumatoid arthritis can cause the knee lining to become inflamed and produce swelling, stiffness, warmth and excess joint fluid.
Joint inflammation may also promote the development of a Baker’s cyst.
Other inflammatory conditions—including gout or, less commonly, joint infection—can also cause substantial knee pain.
A hot, markedly swollen joint with fever or feeling systemically ill deserves timely medical evaluation because septic arthritis is a serious condition.
Could Pain Behind the Knee Come From Your Back or Hip?
Yes.
Pain location does not always identify the actual source.
A review of posterior knee pain recommends examining the lumbar spine and hips because hip pathology, lumbar-facet problems, sacroiliac-region dysfunction and nerve-root irritation can sometimes produce referred pain around the posterior knee.
A referred or neurological source becomes more relevant if posterior knee pain occurs with:
Back pain, buttock pain, tingling, numbness, burning, muscle weakness, or symptoms traveling farther down the leg.
If the knee examination does not explain the symptoms, evaluating the hip and lumbar spine can be important.
Back of Knee Pain When Bending: What Does It Suggest?
Back of knee pain when bending has several possible explanations.
A Baker’s cyst can feel compressed during deeper flexion. A posterior meniscus tear may hurt during bending or twisting. Hamstring or calf injuries can be painful when those tissues change length or contract. Arthritis may make deeper movement generally uncomfortable.
One useful distinction is whether the pain feels like pressure/fullness versus a sharp mechanical catch.
Pressure with a visible lump makes a cyst more plausible.
Sharp pain with twisting, clicking or locking makes meniscal injury more important to consider.
Neither pattern is diagnostic on its own.
Why Does the Back of My Knee Hurt When I Straighten My Leg?
Pain during full extension can occur when a swollen or irritated structure behind the knee becomes tensioned or compressed.
Possible causes include a Baker’s cyst, hamstring or calf tendon irritation, joint inflammation, or meniscal problems.
If you physically cannot straighten the knee rather than simply experiencing pain while doing it, seek an evaluation—especially when locking followed a twisting injury.
Pain Behind the Knee After Running
Runners can develop posterior knee symptoms from several tissues.
Hamstrings, the upper gastrocnemius and the popliteus all cross or act around the posterior knee.
Useful clues include when the symptoms appear.
Pain following sprinting or sudden acceleration may point more toward a hamstring injury.
Upper calf pain following a forceful push-off may involve the gastrocnemius.
Posterolateral discomfort aggravated by downhill running can sometimes involve the popliteus.
Repeatedly continuing the activity through worsening pain can turn a relatively minor overload problem into a more persistent issue.
The Important Exception: Could Pain Behind the Knee Be a Blood Clot?
Most posterior knee pain is musculoskeletal.
But deep vein thrombosis (DVT) must be taken seriously because a blood clot in a deep leg vein can travel to the lungs.
DVT can produce one-sided leg or calf pain, swelling, tenderness, warmth, redness or other skin-color change. Some DVTs produce no obvious symptoms at all.
Risk can be higher after surgery, prolonged immobility or long-distance travel, during pregnancy and postpartum periods, with certain cancers or clotting conditions, and with some estrogen-containing medications.
For authoritative information on warning signs and risk factors, see the CDC guide to blood clots and venous thromboembolism.
When Posterior Knee or Calf Symptoms Need Urgent Attention
| Symptom | Appropriate Response |
| New one-sided calf/leg swelling, warmth, redness or unexplained tenderness | Seek prompt medical assessment for possible DVT |
| Sudden shortness of breath, chest pain, rapid breathing, fainting or coughing blood | Call 911 / seek emergency care for possible pulmonary embolism |
| Hot, very swollen knee with fever | Prompt medical evaluation |
| Knee deformity after significant trauma | Urgent evaluation |
| Inability to bear weight after major injury | Prompt evaluation |
| New persistent numbness, marked weakness or a cold/pale foot | Urgent medical assessment |
A pulmonary embolism can be life-threatening. Mayo Clinic identifies sudden shortness of breath, chest pain, fainting, rapid breathing or pulse, and coughing blood among emergency warning signs.
When Does Back of Knee Pain Need a Non-Emergency Evaluation?
An evaluation is appropriate when symptoms continue beyond a short period, repeatedly return, or begin interfering with normal function.
Particularly useful reasons to get the knee examined include one persistent lump behind the knee, recurrent swelling, repeated catching or locking, instability or buckling, inability to fully bend or straighten the knee, pain following a significant injury, pain that changes how you walk, or symptoms that are progressively worsening.
Cleveland Clinic recommends medical evaluation when posterior knee pain limits movement or routine activity, persists for more than a few days, or is associated with a visible lump, warmth, swelling or fever.
How Is Posterior Knee Pain Diagnosed?
A useful diagnosis usually begins with the story of the pain.
A clinician may ask whether symptoms started suddenly or gradually, whether there was twisting or direct trauma, which activities aggravate the knee, whether you have noticed swelling, whether it locks or gives way, and whether symptoms extend into the calf or farther up the leg.
The examination can evaluate range of motion, joint-line tenderness, swelling, ligament stability, hamstring and calf strength, tendon tenderness, walking pattern, and neurological or vascular findings when relevant.
Do You Need Imaging?
Not always.
The best imaging test depends on the suspected cause.
X-rays can help evaluate arthritis, fractures and other bony problems.
MRI is useful for detailed assessment of structures such as the menisci, ligaments and other soft tissues.
Ultrasound may help identify a Baker’s cyst and is commonly used to evaluate suspected DVT.
Bupa notes that ultrasound may be recommended when a Baker’s cyst is suspected, while MRI may be used for ligament or other internal knee injuries.
The goal is not simply to order as many scans as possible. It is to choose the test that answers the clinical question raised by the history and examination.
What Can You Do at Home for Mild Pain Behind the Knee?
For a minor, clearly activity-related musculoskeletal problem without warning signs, temporarily modifying the activity that triggers pain may be reasonable.
Cold application may help acute soreness or swelling when used with a protective layer between the cold pack and skin.
Gentle, comfortable movement is usually preferable to repeatedly forcing the knee through sharp pain.
Avoid aggressive massage directly over unexplained swelling behind the knee until a clot or vascular problem has been ruled out.
Over-the-counter pain medicine may be appropriate for some people, but medicines such as NSAIDs have potential risks and interactions, so individual medical history matters.
Most importantly, home care should not be used to delay assessment of significant swelling, locking, instability, trauma or possible DVT.
Treatment Depends on the Cause
There is no single knee pain treatment that is appropriate for every form of posterior knee pain.
A hamstring tendon problem requires different rehabilitation from a meniscus tear.
A Baker’s cyst is often managed by addressing the underlying knee condition that is producing excess fluid. Mayo Clinic notes that arthritis and cartilage injuries commonly contribute to Baker’s cyst formation.
Meniscus tears may be treated nonsurgically in many cases, particularly when mechanical locking or major functional problems are absent. AAOS includes physical therapy among nonsurgical treatment options for selected meniscus tears.
Muscle and tendon injuries may involve activity modification followed by progressive flexibility, strength and return to activity.
Arthritis management may include appropriately selected exercise, strength work, activity modification, weight management when relevant and other conservative treatments.
A suspected blood clot requires medical—not musculoskeletal—treatment.
That diagnostic distinction is why persistent posterior knee pain should not simply be labeled “tight hamstrings.”
How Rehabilitation Can Help Posterior Knee Pain
Once serious and structural causes have been appropriately evaluated, rehabilitation may help address common musculoskeletal contributors.
Depending on the condition, treatment can focus on restoring knee motion, strengthening the hamstrings and quadriceps, improving calf and hip strength, rebuilding walking tolerance, improving balance and gradually returning to work, exercise or sports.
AAOS notes that strengthening the muscles around the knee helps support the joint and that flexibility work can help restore range of motion after appropriate evaluation.
The specific exercise matters less than matching the exercise to the diagnosis.
Deep knee-flexion exercises might be reasonable for one patient later in rehabilitation but inappropriate for another person with acute swelling or mechanical locking.
Knee Pain Treatment in Newark, NJ
Persistent posterior knee pain can make walking, climbing stairs, getting out of a chair, driving, working and exercising difficult.
Mount Prospect Health Centre has served patients in the Newark area for more than 25 years, including people from Newark, East Orange, Irvington, Belleville, Bloomfield, Harrison, Kearny and surrounding Essex County communities.
Evaluation can help distinguish common musculoskeletal causes of pain from conditions requiring imaging, medical referral or other care.
Depending on the findings, conservative management may include therapeutic exercise, rehabilitation, soft-tissue or manual techniques when appropriate, mobility work and strategies for gradually restoring normal activity.
Learn more about knee pain treatment in Newark, NJ.
Frequently Asked Questions About Back of Knee Pain
What is the most common cause of pain behind the knee?
There is no single cause in every age group or activity level. Muscle and tendon problems, Baker’s cysts, meniscus injuries and arthritis are among common possibilities. The accompanying symptoms and how the pain started help narrow the diagnosis.
Why does the back of my knee hurt when I bend it?
Possible causes include a Baker’s cyst, meniscus injury, hamstring or calf problem, arthritis or another source of joint swelling. A sharp catch or locking sensation during bending deserves more attention for an internal knee problem such as a meniscus injury.
What causes pain behind the knee when straightening the leg?
A Baker’s cyst, irritated posterior tendons, joint swelling or certain meniscal problems can become uncomfortable during full extension. A large Baker’s cyst may specifically limit full bending or straightening.
Why does my knee hurt after sitting for a long time?
Joint stiffness after rest can occur with knee osteoarthritis. Symptoms may become more noticeable when you first stand and ease somewhat once you start moving.
What does a Baker’s cyst feel like?
It may feel like a soft lump, fullness or pressure behind the knee. Some people experience aching, stiffness or difficulty bending the knee, while others notice little or no pain.
Can a Baker’s cyst go away on its own?
Yes, some cysts improve without direct treatment. In adults, managing the knee condition responsible for excess joint fluid—such as arthritis or cartilage injury—is often important.
Is pain behind the knee a blood clot?
Usually not, but DVT must be considered when pain is accompanied by unexplained one-sided swelling, warmth, redness or tenderness. DVT can also occur without obvious symptoms. Seek prompt medical care when a clot is suspected.
How can you tell a Baker’s cyst from DVT?
You cannot always distinguish them safely at home. A ruptured Baker’s cyst can produce calf pain and swelling similar to a blood clot. Ultrasound and medical evaluation may be needed.
Can a meniscus tear hurt behind the knee?
Yes. Depending on where the meniscus is injured, pain can be felt toward the posterior knee. Bending or twisting may aggravate it, and clicking, catching, swelling or locking can occur.
Can tight hamstrings cause pain behind the knee?
Hamstring muscle or tendon problems can produce posterior knee discomfort. Persistent focal tendon pain—particularly when triggered by activity—should not simply be assumed to be harmless tightness.
Can sciatica cause pain behind the knee?
Nerve-root irritation from the lumbar spine can refer symptoms toward the knee or farther down the leg. Tingling, numbness, burning sensations, back pain or pain extending beyond the knee make a neurological source more important to consider.
Is walking good for pain behind the knee?
It depends on the cause. Gentle walking may be appropriate for many minor musculoskeletal problems or arthritis, but you should not force walking through severe pain, instability, significant swelling or an acute injury. Suspected DVT requires medical evaluation rather than an exercise program.
Should I stretch the back of my knee?
Gentle hamstring or calf stretching can be useful for selected muscle and tendon problems, but stretching is not appropriate treatment for every cause of posterior knee pain. Do not aggressively stretch a swollen, locked, recently traumatized or unexplained painful knee.
When should I worry about posterior knee pain?
Seek evaluation for persistent pain, a new lump, marked swelling, locking, instability, inability to bear weight or difficulty fully moving the knee. Seek prompt medical care for possible DVT symptoms and emergency care if leg symptoms occur with chest pain or difficulty breathing.
The Bottom Line
Back of knee pain is a location—not a diagnosis.
Pain after running or exercise may come from the hamstring, calf or another posterior tendon.
A feeling of fullness or a lump can indicate a Baker’s cyst.
Pain with bending, twisting, clicking or locking may point toward the meniscus.
Pain after a force to the front of a bent knee can involve the PCL.
Stiffness after sitting can occur with arthritis.
And unexplained one-sided calf swelling, warmth, redness or tenderness requires prompt medical attention because a blood clot must be ruled out.
The most useful next step is to pay attention to the pattern: how the pain started, which movement triggers it, whether swelling is present, whether the joint catches or gives way, and whether symptoms extend into the calf or farther down the leg.
When posterior knee pain persists or interferes with walking and everyday activity, a professional evaluation can help identify which structure is actually involved and guide the appropriate treatment instead of treating every case as the same generic knee problem.