Pain Behind the Knee
Pain behind the knee, also called posterior knee pain, may feel like aching, tightness, pressure, sharp pain, fullness or a lump in the hollow at the back of the joint. It may develop gradually with arthritis or swelling, begin after running or sport, follow a twist or direct injury, or appear suddenly with calf swelling.
The posterior knee contains hamstring and calf tendons, the popliteus, posterior capsule, menisci, ligaments, nerves, arteries, veins and fluid-filled bursae. Pain in this region is therefore a location—not a diagnosis. The first priority is to distinguish common mechanical causes from a blood clot, infection, vascular problem, fracture or major ligament injury.
For the broader diagnosis-first pathway, read Knee Pain Treatment in Mumbai. Patients who also notice visible fluid can review Knee Swelling and Water in the Knee.
Quick Answer: What Commonly Causes Pain Behind the Knee?
Common causes include a Baker’s cyst, knee osteoarthritis with joint fluid, hamstring or calf-tendon irritation, popliteus overload, posterior meniscal pathology, muscle strain and stiffness from loss of full knee extension. Ligament injuries and pain referred from the hip or spine are also possible.
Sudden calf swelling, warmth, colour change or tenderness—especially with breathlessness or chest pain—requires urgent assessment because deep-vein thrombosis and pulmonary embolism must be excluded. A ruptured Baker’s cyst can look similar, so the cause should not be self-diagnosed.
Where Exactly Is the Posterior Pain?
Central Fullness or a Lump Behind the Knee
A visible or palpable lump that changes in size or feels tight during bending may be a Baker’s cyst. A cyst usually reflects extra fluid generated by another knee condition rather than a separate disease. A pulsating mass is not typical of an ordinary cyst and needs urgent vascular assessment.
Inner-Posterior Pain
Pain toward the inner back of the knee may involve the medial hamstring tendons, posterior horn of the medial meniscus, medial compartment, posterior capsule or a Baker’s cyst. Joint-line pain with twisting, swelling, catching or locking raises concern for a meniscal component.
Outer-Posterior Pain
Posterolateral pain may involve the popliteus, biceps femoris tendon, lateral meniscus, proximal tibiofibular joint or posterolateral ligament structures. Running downhill, twisting or direction changes can reproduce symptoms. See Outer Knee Pain.
Pain Extending Into the Calf
Upper-calf strain, a ruptured Baker’s cyst and deep-vein thrombosis can all cause pain extending below the knee. Calf swelling, warmth, redness, risk factors for thrombosis, recent surgery, prolonged travel or shortness of breath increase urgency. Do not massage an unexplained swollen calf until a clot has been excluded.
Common Causes of Pain Behind the Knee
Baker’s Cyst
A Baker’s cyst is a fluid-filled swelling at the back of the knee. It commonly develops when osteoarthritis, a meniscal problem, inflammatory arthritis or another intra-articular condition produces excess fluid. Symptoms can include pressure, tightness, reduced bending, discomfort at full extension and a lump that becomes more or less prominent with knee position.
Treatment focuses on the underlying knee condition. Aspiration may reduce pressure in selected large symptomatic cysts, but recurrence is possible if the joint continues to produce fluid. Isolated cyst surgery is uncommon. Sudden calf pain and swelling can occur if a cyst ruptures, but DVT must be excluded because the symptoms overlap.
Knee Osteoarthritis and Joint Effusion
Osteoarthritis can cause posterior pain through inflammation, fluid accumulation, reduced extension, posterior-capsule tightness and formation of a Baker’s cyst. Associated symptoms may include activity pain, brief stiffness after rest, reduced walking distance, stair difficulty, crepitus and deformity. Early and moderate disease can often be managed without surgery.
Read Knee Arthritis Treatment in Mumbai and Non-Surgical Knee Arthritis Treatment in Mumbai.
Hamstring Tendon Pain
The hamstring tendons attach around the inner and outer back of the knee. Irritation may follow sprinting, sudden acceleration, hill running, gym training, excessive stretching or a rapid increase in activity. Pain is often localised and reproduced by resisted knee bending. Rehabilitation generally uses temporary load reduction and progressive strengthening rather than prolonged rest or aggressive stretching.
Gastrocnemius or Upper-Calf Strain
The gastrocnemius crosses the knee and can be strained during running, jumping or forceful push-off. Pain may be accompanied by bruising, tenderness or difficulty walking and standing on the toes. Swelling and warmth require consideration of a clot rather than an automatic muscle-strain diagnosis.
Popliteus and Posterolateral Soft-Tissue Pain
The popliteus helps initiate knee bending and control rotation. Irritation may cause posterolateral pain during downhill running, twisting or repeated flexion. Other nearby tendons can create similar symptoms, so the diagnosis depends on examination rather than location alone.
Posterior Meniscal Pathology
The posterior horn of the medial or lateral meniscus may produce pain after a twist, deep squat or degenerative change. Symptoms can include joint-line pain, swelling, catching, clicking or true locking. Degenerative tears frequently coexist with arthritis and do not automatically require arthroscopy. See Knee Locking and Catching.
Posterior Cruciate or Complex Ligament Injury
PCL injury can follow a force to the front of a bent knee, a dashboard injury or a fall directly onto the knee. Pain, swelling and instability may occur. Complex multi-ligament injuries can threaten nerves or blood vessels and need timely specialist care. Significant sports-ligament reconstruction falls outside Dr. Mayur Rabhadiya’s primary arthritis and joint-replacement focus and should be referred appropriately.
Deep-Vein Thrombosis
A blood clot in the deep veins may cause calf or posterior-knee pain, swelling, warmth, colour change or tenderness. Risk can increase after surgery, hospitalisation, prolonged immobility, long travel, previous thrombosis, cancer, pregnancy or certain medicines. DVT cannot be reliably diagnosed or excluded from symptoms alone; urgent medical assessment and vascular ultrasound may be required.
Arterial or Other Vascular Problems
A pulsating lump behind the knee, a cold pale foot, severe sudden pain, reduced pulses or neurological change may indicate a vascular emergency such as a popliteal-artery problem. These symptoms require urgent hospital assessment. Vascular causes should not be massaged or treated as a muscle knot.
Pain Referred From the Hip, Spine or Nerves
Hip arthritis, lumbar nerve irritation and spinal stenosis can produce pain around or behind the knee. Groin pain, back pain, numbness, tingling, weakness or symptoms extending down the leg are useful clues. The hip, spine and neurological system should be examined when knee findings do not explain the symptoms.
Posterior Knee Pain During Common Activities
Pain While Walking or Standing
Arthritis, a Baker’s cyst, reduced extension, meniscal irritation, tendon pain and calf problems can cause symptoms during walking. Progressive loss of walking distance, limping, calf swelling or rest pain deserves assessment. See Knee Pain While Walking.
Pain During Deep Bending or Squatting
Deep flexion can compress a cyst, swollen joint or posterior meniscus and stretch irritated tissues. Pain only at maximum depth may improve when squat range is temporarily reduced, but swelling, locking or injury requires evaluation. See Knee Pain While Squatting.
Pain After Sitting or During Full Extension
A swollen or arthritic knee may feel tight after prolonged sitting and painful when first straightened. A Baker’s cyst can become tense near full flexion or extension. Persistent loss of full extension should be examined rather than repeatedly forced.
Pain After Running or Exercise
Hamstring, calf and popliteus problems may follow sprinting, hills, acceleration, deceleration or a rapid increase in training. Meniscal and stress injuries are also possible. See Knee Pain After Running or Exercise.
Pain After Knee Surgery or Replacement
Temporary posterior tightness may occur during recovery because of swelling, limited extension and muscle guarding. New calf swelling, wound drainage, fever, increasing redness, severe pain or sudden loss of function needs urgent review. Persistent pain months or years after replacement requires evaluation for infection, loosening, instability, stiffness, referred pain and other causes.
How Pain Behind the Knee Is Evaluated
Assessment includes the exact location, presence of a lump, knee and calf swelling, warmth, redness, injury or surgery history, relationship to walking, running, bending or sitting, clicking, locking, instability, breathlessness and vascular risk factors. Examination may assess the knee, calf, tendons, menisci, ligament stability, pulses, circulation, neurological function, hip and spine.
When Are X-Rays, Ultrasound, MRI or Blood Tests Needed?
Standing weight-bearing X-rays may be useful when osteoarthritis, deformity or fracture is suspected. Ultrasound can identify a Baker’s cyst, assess superficial tendons and examine deep veins when thrombosis is suspected. MRI may be considered after significant injury, true locking, unexplained recurrent swelling or suspected meniscal, ligament, cartilage or bone pathology when the result will change management.
Blood tests, joint-fluid analysis or vascular imaging may be required when infection, inflammatory arthritis, gout, bleeding or a vascular problem is suspected. A hot swollen joint may need aspiration rather than routine MRI alone.
Treatment Without Surgery
Treat the Underlying Cause
A Baker’s cyst, osteoarthritis flare, tendon strain, meniscal problem and blood clot require completely different treatment. Management should begin only after urgent vascular, infectious and major traumatic causes have been considered.
Activity Modification and Symptom Control
For a non-urgent mechanical flare, temporarily reduce painful running, deep bending, hills, repeated stairs or prolonged standing while preserving safe movement. Cold, elevation and appropriate compression may help selected cases of joint swelling. Compression should not produce increasing calf pain, numbness or colour change.
Therapeutic Exercise and Physiotherapy
A diagnosis-specific programme may include knee movement, quadriceps, hamstring and calf strengthening, hip strength, gait and balance work and graded return to walking or running. Aggressive massage, stretching or exercise should not begin when DVT, infection, fracture or major ligament injury has not been excluded.
Baker’s Cyst Aspiration and Recurrence
A large symptomatic cyst or joint effusion may occasionally be aspirated under sterile conditions, often with imaging guidance. Fluid may be analysed if infection, gout or bleeding is possible. Aspiration can reduce pressure but does not guarantee that fluid will not return. Treating arthritis or inflammation inside the knee is usually more important than repeatedly draining the cyst.
Medicines, Weight Management and Injections
Medicines should be selected after considering kidney, stomach, heart, liver and medication risks. For people living with overweight or obesity and osteoarthritis, sustainable weight reduction can improve pain and function. A corticosteroid injection may provide short-term relief for selected osteoarthritis patients. Evidence and recommendations differ for hyaluronic acid, PRP, GFC and other injections. None treats DVT, infection, vascular disease, tendon rupture or every Baker’s cyst, and none should be presented as guaranteed cartilage regeneration.
When Is Surgery or Knee Replacement Considered?
Most posterior knee pain does not require surgery. Selected traumatic meniscal or ligament injuries, fractures, infection and vascular conditions may need specialist intervention. Baker’s-cyst surgery is uncommon and generally considered only when symptoms remain substantial after the underlying joint condition has been addressed.
Knee replacement may be considered only when confirmed advanced arthritis causes substantial pain, recurrent swelling, severe stiffness, deformity, reduced walking, sleep disturbance or loss of independence despite suitable non-surgical care. Posterior pain or a Baker’s cyst alone is not an indication.
Robotic assistance supports planning and execution but does not replace surgical judgement. Dr. Mayur Rabhadiya combines robotic planning with a minimally invasive mini-subvastus, muscle-sparing approach in suitable patients without promising a painless or guaranteed rapid recovery. Read When Does Knee Arthritis Need Replacement?.
Warning Signs That Need Urgent Assessment
Sudden calf swelling, warmth, tenderness, redness or colour change
Breathlessness, chest pain, coughing blood, fainting or collapse
A pulsating mass behind the knee or a cold, pale or numb foot
A hot, red, rapidly swollen and severely painful knee
Fever, chills or feeling systemically unwell
Inability to bear weight after injury, visible deformity or rapid large swelling
A physically locked knee or repeated severe giving way
New wound drainage, fever or sudden deterioration after knee surgery
Questions Patients Commonly Ask
Is pain behind the knee usually a Baker’s cyst?
A Baker’s cyst is common, especially with arthritis or joint swelling, but tendons, menisci, ligaments, nerves and blood vessels can produce similar symptoms.
How can I tell a Baker’s cyst from a blood clot?
Symptoms can overlap. Sudden calf swelling, warmth, tenderness or colour change requires urgent assessment. Ultrasound may be required; self-diagnosis is unsafe.
Can a Baker’s cyst rupture?
Yes. Fluid can track into the calf and cause sudden pain and swelling. DVT must still be excluded because it can look similar.
Should I massage a painful swollen calf?
No. Do not massage an unexplained swollen calf until a blood clot, vascular problem and significant muscle injury have been assessed.
Can arthritis cause pain behind the knee?
Yes. Arthritis can produce joint fluid, reduced extension, posterior-capsule tightness and a Baker’s cyst.
Why does it hurt when I fully straighten my knee?
A tense cyst, swelling, arthritis, posterior-capsule tightness or tendon problem can make full extension painful. Persistent loss of extension should be examined.
Why does it hurt when I bend deeply or squat?
Deep flexion can compress a cyst, swollen joint or posterior meniscus and stretch irritated tissues. Swelling, locking or injury history changes the significance.
Can running cause pain behind the knee?
Yes. Hamstring, gastrocnemius and popliteus overload, meniscal pathology and stress injury are possible, especially after sudden changes in speed, hills or training volume.
Can a meniscus tear cause posterior pain?
Yes, particularly when the posterior horn is involved and pain follows twisting or deep bending with swelling, catching or locking. Degenerative tears may coexist with arthritis.
Should every Baker’s cyst be drained?
No. Many improve when the underlying knee condition is treated. Aspiration is reserved for selected symptomatic cases, and recurrence is possible.
Can a Baker’s cyst be cancer?
A typical Baker’s cyst is benign, but an unusual, hard, enlarging, pulsating or unexplained mass should be assessed rather than assumed to be a cyst.
Do I need an ultrasound or MRI?
Ultrasound is useful for a cyst, superficial structures and venous assessment. MRI is considered for deeper structural questions when the result is likely to change treatment.
Can physiotherapy help?
Yes, for many mechanical causes when the programme matches the diagnosis. It should not begin aggressively before DVT, infection, fracture or major injury has been excluded.
Can GFC or PRP help posterior knee pain?
They are not treatments for every posterior pain or Baker’s cyst. They may be discussed only for a suitable diagnosed arthritic condition and stage, with transparent evidence and limitations.
Does a Baker’s cyst mean I need knee replacement?
No. Replacement is considered only when the underlying advanced arthritis substantially affects overall function and quality of life despite suitable care.
Clinical References and Further Reading
NICE NG226: Osteoarthritis in over 16s—diagnosis and management
About Dr. Mayur Rabhadiya
Dr. Mayur Rabhadiya is an Orthopedic and Joint Replacement Surgeon in Mumbai. His focused knee practice includes diagnosis-first knee pain evaluation, staged treatment of knee arthritis, selected non-surgical care and minimally invasive mini-subvastus robotic knee replacement when clinically indicated. Significant sports-ligament, vascular and specialist meniscal conditions are referred appropriately. His qualifications are MBBS, D’Ortho, DNB (Orthopedics), MNAMS (Orthopedics) and FIJR (Robotic & Navigation).
Last medically reviewed: 24 July 2026. Medical reviewer: Dr. Mayur Rabhadiya.
Book a Knee Consultation in Mumbai
Patients with persistent posterior knee pain, a Baker’s cyst, swelling, stiffness or uncertainty about treatment can consult Dr. Mayur Rabhadiya in Ghatkopar East or Ghatkopar West, Mumbai. Call or WhatsApp +91 84249 03913 or +91 96113 30063, or use the orthopedic appointment page. Urgent vascular or postoperative warning signs should be assessed through emergency care rather than waiting for a routine appointment.
Medical Disclaimer
This guide provides general education and does not replace individual medical assessment. Seek urgent care for sudden calf swelling, chest pain, breathlessness, a pulsating mass, a cold pale foot, a hot swollen knee with fever, severe injury, inability to bear weight, true locking or postoperative wound concerns.