Medically Reviewed By: Mark Aquino, NP – Urgent Care Nurse Practitioner, author of Physical Assessment for Nurses Simplified. This article is based on real-world urgent care experience and current clinical guidelines.
Knee pain is extremely common, but not all knee pain comes from the same problem. Where the pain occurs—at the front, back, inside, or outside of the knee—can provide important clues about what may be causing it.
Pain around the kneecap after running may have a very different cause from sudden pain behind the knee with calf swelling. Similarly, pain along the inner knee after a twisting injury raises different possibilities than gradually worsening knee stiffness in an older adult.
The knee contains bones, cartilage, menisci, ligaments, tendons, muscles, bursae, and other structures that work together to support body weight and allow movement. Injury or inflammation involving any of these structures can cause knee pain.[1]
This guide explains common knee pain causes by location, symptoms that may help distinguish them, what you can do at home, when urgent care may be appropriate, and when knee pain could represent an emergency.
Important: Pain location can help narrow the possibilities, but it cannot diagnose the cause by itself. Several knee conditions produce overlapping symptoms, and an examination or imaging may sometimes be necessary.
Knee Pain Location: A Quick Guide
The following is a general guide rather than a diagnostic chart.
| Where it hurts | Some common possibilities |
|---|---|
| Front of knee | Patellofemoral pain, patellar tendinopathy, bursitis, osteoarthritis |
| Around/behind kneecap | Patellofemoral pain, cartilage irritation, osteoarthritis |
| Inner knee | MCL injury, medial meniscus injury, osteoarthritis, pes anserine bursitis |
| Outer knee | IT band syndrome, LCL injury, lateral meniscus injury |
| Back of knee | Baker cyst, hamstring injury, arthritis, meniscus injury |
| Entire knee | Osteoarthritis, inflammatory arthritis, significant injury |
| Hot, red, swollen knee | Gout, pseudogout, infection/septic arthritis |
| Knee plus calf swelling | Baker cyst, injury, or potentially DVT |
Symptoms such as swelling, instability, locking, fever, inability to bear weight, or the mechanism of an injury are often just as important as the location of the pain.
Front of Knee Pain
Pain in the front of the knee is often called anterior knee pain. It may be centered around or underneath the kneecap.
Several conditions can produce this pattern.
1. Patellofemoral Pain
Patellofemoral pain is a common cause of pain around or behind the kneecap.
People may describe a dull or aching discomfort that becomes worse with activities that repeatedly bend the knee, including:
- Running
- Squatting
- Jumping
- Climbing stairs
- Sitting with the knee bent for a long time
Popping or crackling may also occur.[2]
Patellofemoral pain is particularly common in physically active adolescents and younger adults, although it can occur at other ages.
Unlike a major ligament or meniscus injury, there may be no single traumatic event.
2. Patellar Tendinopathy
The patellar tendon connects the kneecap to the tibia.
Repeated jumping, running, or other high-impact activities can overload this tendon and cause pain near the lower portion of the kneecap.
This is sometimes called jumper’s knee.
Pain often worsens with:
- Jumping
- Running
- Squatting
- Stairs
- Repeated knee extension
3. Prepatellar Bursitis
A bursa is a small fluid-filled sac that reduces friction between tissues.
The prepatellar bursa sits in front of the kneecap. Repeated kneeling or direct trauma can irritate it.
The front of the knee may become visibly swollen and tender.
Occupations or activities involving frequent kneeling can increase the risk.
Pain Around or Behind the Kneecap
Pain that feels as though it comes from underneath or behind the kneecap frequently overlaps with anterior knee pain.
Patellofemoral pain is one possibility, but cartilage changes and osteoarthritis can also cause discomfort in this area.
A clinician may ask whether the pain worsens when:
- Going downstairs
- Squatting
- Running
- Standing after prolonged sitting
- Sitting with the knee bent
These details can help narrow the differential diagnosis.
Inner Knee Pain
Pain on the inside of the knee is called medial knee pain.
Several important structures are located here.
1. Medial Collateral Ligament Injury
The medial collateral ligament (MCL) runs along the inner portion of the knee and helps control side-to-side movement.
MCL injuries commonly occur when a force strikes the outside of the knee, pushing the knee inward.[1]
Symptoms may include:
- Inner knee pain
- Tenderness along the ligament
- Swelling
- Instability with more significant injuries
A sports collision is one possible mechanism.
2. Medial Meniscus Injury
The menisci are cartilage structures that act partly as shock absorbers between the femur and tibia.
A meniscus can tear when the knee twists or pivots, particularly when the foot remains planted.[1]
Symptoms can include:
- Joint-line pain
- Swelling
- Clicking or catching
- Difficulty fully bending or straightening the knee
- Locking
- Pain with twisting
Degenerative meniscus tears can also occur without a dramatic injury, particularly as people get older.
3. Knee Osteoarthritis
Osteoarthritis can affect different parts of the knee and commonly produces pain, stiffness, and reduced function.
Symptoms often develop gradually rather than immediately after an injury.
People may notice:
- Pain with walking or prolonged activity
- Stiffness after inactivity
- Reduced range of motion
- Grinding or crepitus
- Intermittent swelling
Persistent knee pain does not automatically mean arthritis, however, and an examination may be needed to determine the cause.
4. Pes Anserine Bursitis
The pes anserine bursa is located along the inner upper tibia below the knee joint.
Inflammation can cause pain and tenderness along the inner knee, often slightly below the joint itself.
Outer Knee Pain
Pain on the outside of the knee is called lateral knee pain.
1. Iliotibial Band Syndrome
The iliotibial band, or IT band, runs along the outside of the thigh toward the knee.
Repetitive friction and overuse can produce lateral knee pain, particularly in runners and cyclists.
The pain may become progressively worse during activity and improve with rest.
2. Lateral Collateral Ligament Injury
The lateral collateral ligament (LCL) helps stabilize the outer knee.
A force pushing the knee outward can injure this ligament.[1]
Symptoms can include lateral tenderness, pain, swelling, or instability.
3. Lateral Meniscus Injury
The lateral meniscus can also be injured during twisting or pivoting.
As with other meniscal injuries, symptoms may include:
- Outer joint-line pain
- Swelling
- Catching
- Clicking
- Locking
- Pain with twisting
Pain Behind the Knee
Pain behind the knee deserves particular attention because the possible causes range from relatively minor musculoskeletal conditions to vascular problems requiring urgent evaluation.
Baker Cyst
A Baker cyst, also called a popliteal cyst, is a fluid-filled swelling behind the knee.
It can develop when another knee problem causes excess joint fluid.
A person may notice:
- Fullness behind the knee
- Tightness
- A palpable lump
- Discomfort when fully bending or straightening the knee
A Baker cyst can occasionally rupture and cause calf pain and swelling.
That creates an important diagnostic problem because a ruptured Baker cyst can resemble a blood clot.
If one leg becomes suddenly swollen—especially when swelling extends into the calf—read One Swollen Leg: Causes, Blood Clot Warning Signs, and When to Seek Care.
Hamstring or Tendon Injury
The hamstring muscles and tendons cross the back of the knee.
Strains can cause posterior knee pain, particularly following running, sprinting, sudden acceleration, or overstretching.
Meniscus or Arthritis
Problems inside the knee joint can sometimes produce pain that is perceived primarily toward the back of the knee.
For that reason, pain location alone cannot reliably identify the affected structure.
Knee Pain and Swelling
Swelling provides another important clue.
A swollen knee may develop after:
- Ligament injury
- Meniscus injury
- Fracture
- Osteoarthritis
- Bursitis
- Gout
- Inflammatory arthritis
- Joint infection
The speed at which swelling develops can also matter.
Rapid swelling after a significant injury may suggest bleeding or substantial internal joint injury. Gradual swelling can occur with overuse or arthritis.
A suddenly hot, red, extremely painful swollen joint, particularly when accompanied by fever or systemic illness, requires prompt medical evaluation because infection must be considered.
NICE recommends assessing septic arthritis in people presenting with a painful, red, swollen joint and immediate referral when septic arthritis is suspected.[3]
Could Knee Pain Be a Blood Clot?
A blood clot in a deep vein—deep vein thrombosis (DVT)—does not originate in the knee joint itself. However, discomfort behind the knee or upper calf can sometimes be perceived as knee-region pain.
More concerning symptoms include:
- One-sided calf or leg swelling
- New calf tenderness
- Warmth
- Skin discoloration
- Unexplained swelling extending beyond the knee
The concern becomes greater when risk factors are present, such as recent surgery, prolonged immobilization, previous DVT, certain cancers, pregnancy/postpartum status, or prolonged travel.
A physical examination alone cannot reliably exclude every DVT. Ultrasound is commonly used when the clinical evaluation suggests a blood clot may be present.
For a detailed explanation of unilateral swelling and blood-clot warning signs, see Leg Swelling: Causes, When It’s Dangerous, and When to Seek Care.
If leg symptoms are accompanied by new shortness of breath, chest pain, coughing blood, fainting, or severe breathing difficulty, seek emergency medical care because a clot can travel to the lungs.
Knee Pain After an Injury
How the injury happened can be as informative as where the knee hurts.
For example:
Twisting or pivoting: may injure the meniscus or ACL.
Direct blow to the outside of the knee: may injure the MCL.
Direct blow to the front of a bent knee: can injure the PCL.[1]
Sudden change in direction or awkward landing: can injure the ACL.
Fall directly onto the knee: can cause contusion, bursitis, patellar injury, or fracture.
Repeated running or jumping: makes overuse conditions such as patellofemoral pain and tendinopathy more likely.
A popping sensation accompanied by immediate instability or substantial swelling deserves medical evaluation.
Why Is My Knee Popping or Clicking?
Not every noise coming from the knee represents an injury.
Popping, cracking, or grinding can occur without serious disease.
However, clicking or popping becomes more significant when accompanied by:
- Pain
- Swelling
- Locking
- Catching
- Instability
- Recent trauma
Mechanical symptoms after an injury can raise suspicion for internal knee damage such as a meniscal or ligament injury. AAOS notes that knee injuries can cause catching or locking and that ACL injuries may produce a sensation that the knee is giving way.[1]
What Does a Locked Knee Mean?
A truly locked knee means the person cannot completely bend or straighten it because something is mechanically preventing normal movement.
Meniscus injuries are one possible cause.
This differs from someone avoiding movement simply because bending the knee hurts.
Persistent locking deserves medical assessment, particularly after an injury.
Why Does My Knee Give Out?
A sensation that the knee is buckling or giving way can occur from pain, muscle weakness, or structural instability.
Ligament injuries—particularly ACL injuries—can produce instability.[1]
Repeated episodes of the knee giving way should be evaluated because recurrent instability may increase the risk of additional injury.
Knee Pain When Walking
Pain during walking can occur with many knee conditions.
The pattern provides useful information.
Pain that develops after prolonged activity can occur with overuse conditions or arthritis.
Pain after twisting or trauma raises greater concern for injury.
Pain associated with significant swelling, instability, or inability to bear weight warrants earlier evaluation.
Knee Pain When Going Up or Down Stairs
Stairs place substantial demand on the knee.
Pain around the kneecap during stairs is commonly associated with patellofemoral problems.
Anterior knee pain can also worsen during squatting, running, jumping, or prolonged sitting.[2]
However, stair pain is not specific enough to diagnose a particular condition on its own.
Knee Pain After Running
Running-related knee pain can result from:
- Patellofemoral pain
- IT band syndrome
- Tendinopathy
- Bursitis
- Training errors
- Muscle weakness or imbalance
- Less commonly, stress injury or another structural problem
Consider whether something recently changed:
- Mileage
- Running intensity
- Hills
- Footwear
- Running surface
- Frequency of training
Rapid increases in training load can contribute to overuse injuries.
How Is Knee Pain Diagnosed?
A clinician usually begins by asking detailed questions about the symptoms.
Important information includes:
- Exact location of pain
- Sudden versus gradual onset
- Recent trauma
- Mechanism of injury
- Swelling
- Fever
- Locking or catching
- Instability
- Ability to bear weight
- Previous knee injuries
- Sports and occupational activity
- Medical conditions
The examination may evaluate range of motion, swelling, tenderness, strength, stability, gait, and specific structures within the knee.
Do You Need an X-Ray for Knee Pain?
Not everyone with knee pain needs immediate imaging.
An X-ray is particularly useful when fracture or significant bony disease is suspected.
Depending on the situation, clinicians may use decision rules to determine whether radiographs are appropriate after an acute knee injury.
X-rays can also help evaluate osteoarthritis and other bony abnormalities.
However, many important structures—including the menisci, ligaments, and tendons—are soft tissues and are not directly visualized well on routine X-rays.
When Is an MRI Needed?
MRI provides much more detail about soft tissues.
It can help evaluate structures such as:
- ACL
- PCL
- Menisci
- Cartilage
- Tendons
- Other internal knee structures
But an MRI is not automatically necessary for every painful knee.
A clinician may initially recommend conservative treatment when the examination suggests a minor injury and there are no concerning findings.
MRI becomes more useful when symptoms persist, significant internal injury is suspected, mechanical symptoms are present, or the result would change management.
Knee Pain Treatment at Home
For many minor knee injuries and overuse conditions, initial conservative treatment is reasonable.
AAOS recommends measures including rest, ice, compression, and elevation for many acute knee injuries.[1]
Relative Rest
Temporarily reduce activities that clearly aggravate the pain.
Complete inactivity is not always necessary.
The goal is often to reduce the activity enough to allow irritated tissues to recover while maintaining safe movement.
Ice
Cold therapy may reduce pain and swelling after an acute injury.
A cold pack can be used for approximately 20 minutes at a time, with a barrier between the cold source and the skin.[1]
Avoid applying ice directly to bare skin.
Compression
A soft elastic knee wrap may help control swelling.
It should be snug but not so tight that it causes numbness, tingling, discoloration, or worsening pain.
Elevation
Elevating the leg while resting may help reduce swelling.
Medication for Knee Pain
Over-the-counter pain medicines may be appropriate for some people.
Options may include acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen.
However, NSAIDs are not appropriate for everyone.
People with kidney disease, gastrointestinal ulcers or bleeding, certain cardiovascular conditions, anticoagulant use, pregnancy, medication interactions, or other medical conditions should discuss NSAID use with a healthcare professional.
Follow the product label unless your healthcare professional gives you different instructions.
Medication can reduce symptoms, but persistent pain should not simply be masked without determining why it continues.
Exercises and Physical Therapy for Knee Pain
Exercise is an important component of treatment for many knee conditions.
Physical therapy may focus on strengthening:
- Quadriceps
- Hamstrings
- Hip muscles
- Gluteal muscles
- Other stabilizing muscles
Flexibility and movement mechanics may also be addressed.
AAOS identifies physical therapy as an important nonsurgical treatment for many knee injuries.[1]
However, the appropriate exercises depend on the diagnosis.
A rehabilitation program for patellofemoral pain will not necessarily be appropriate for an acute ligament tear or fracture.
If an exercise produces significant pain, instability, or worsening swelling, stop and seek clinical guidance rather than forcing through the symptoms.
When Should You Go to Urgent Care for Knee Pain?
Urgent care may be appropriate for knee pain when you need timely evaluation but do not appear to have a limb- or life-threatening emergency.
Examples include:
- Persistent knee pain
- Moderate swelling
- Suspected sprain
- Minor sports injury
- Pain after a fall when you can still bear weight
- Suspected overuse injury
- Pain that is not improving with home treatment
Depending on the facility, urgent care may be able to perform an examination and obtain X-rays.
More complicated ligament or meniscal injuries may ultimately require follow-up with primary care, sports medicine, physical therapy, or orthopedics.
When Knee Pain May Be an Emergency
Some knee symptoms should not wait for a routine appointment.
Seek prompt or emergency medical evaluation for:
A severely deformed knee after an injury
A fracture or dislocation may be present.
Loss of circulation or sensation below an injured knee
A cold or pale foot, absent pulses, severe numbness, or major weakness can indicate neurovascular injury.
A hot, red, severely painful swollen knee with fever
Septic arthritis must be considered. Suspected septic arthritis requires immediate medical evaluation because untreated infection can rapidly damage the joint.[3]
Sudden severe leg swelling or calf swelling
DVT should be considered, particularly in someone with blood-clot risk factors.
Knee/leg symptoms with chest pain or shortness of breath
This raises concern for pulmonary embolism and requires emergency evaluation.
Because chest symptoms can have many causes, see Chest Pain: Causes, Warning Signs, and When to Go to the ER for additional red flags.
Inability to bear weight following significant trauma
Fracture or significant internal injury may be present.
Major swelling immediately after an injury
Rapid swelling can accompany significant ligament or internal joint injury.
When Should You See a Doctor for Knee Pain?
Schedule an evaluation if knee pain:
- Persists despite home treatment
- Repeatedly returns
- Interferes with walking or daily activities
- Causes recurrent swelling
- Causes instability
- Causes locking or catching
- Limits normal range of motion
- Follows a significant injury
- Progressively worsens
Earlier assessment can help identify conditions that benefit from rehabilitation or other treatment before they become chronic.
How Long Does Knee Pain Take to Heal?
Recovery depends entirely on the cause.
Minor irritation or overuse may improve over days to several weeks.
Mild sprains may require several weeks.
More substantial ligament or meniscus injuries can require substantially longer rehabilitation.
Some chronic conditions, such as osteoarthritis, are managed rather than permanently “healed.”
The severity of the injury, age, activity demands, underlying health, rehabilitation, and adherence to treatment all influence recovery.
Can You Prevent Knee Pain?
Not every knee problem can be prevented, but several strategies may reduce risk.
Increase Exercise Gradually
Avoid suddenly increasing running mileage, intensity, or repetitive high-impact activity.
Strengthen the Muscles Supporting the Knee
Strong quadriceps, hamstrings, hip muscles, and gluteal muscles help control forces passing through the knee.
Use Appropriate Technique
Poor landing mechanics and abrupt changes in direction can increase stress on knee structures.
Allow Adequate Recovery
Repeatedly training through significant pain can worsen some overuse injuries.
Maintain a Healthy Body Weight
Excess body weight increases mechanical load on weight-bearing joints, including the knees.
Frequently Asked Questions About Knee Pain
What causes knee pain without an injury?
Common possibilities include osteoarthritis, patellofemoral pain, tendinopathy, bursitis, inflammatory arthritis, gout, overuse, and other conditions. The pattern of symptoms and examination findings help determine the cause.
What causes pain behind the knee?
Possible causes include a Baker cyst, hamstring or tendon injury, arthritis, meniscal problems, and other musculoskeletal conditions. Calf or leg swelling also raises concern for DVT.
What causes inner knee pain?
Medial meniscus injuries, MCL injuries, osteoarthritis, and pes anserine bursitis are among the possibilities.
What causes outer knee pain?
IT band syndrome, LCL injury, lateral meniscus problems, and other conditions can cause lateral knee pain.
Why does the front of my knee hurt?
Patellofemoral pain and patellar tendon problems are common possibilities. Symptoms related to stairs, running, squatting, jumping, or prolonged sitting can provide additional clues.
Should I exercise with knee pain?
It depends on the cause and severity. Mild discomfort from some overuse conditions may improve with activity modification and appropriate rehabilitation, while suspected fractures, significant ligament injuries, severe swelling, or unstable knees require evaluation before returning to strenuous activity.
Is walking good for knee pain?
For many chronic conditions, comfortable low-impact activity can be beneficial. Walking should not be forced when it causes substantial pain, instability, or worsening swelling.
Why is my knee swollen but not painful?
Fluid can accumulate for several reasons, including bursitis, joint effusion, arthritis, or prior injury. Persistent or unexplained swelling deserves evaluation even when pain is minimal.
Can knee pain come from the back?
Yes. Nerve irritation or other conditions involving the lower back can sometimes produce symptoms that travel into the leg and may be perceived around the knee.
The Bottom Line
The location of knee pain can provide useful clues, but it does not establish a diagnosis by itself.
Front knee pain commonly occurs with patellofemoral or tendon problems. Inner knee pain may involve the MCL, medial meniscus, or arthritis. Outer knee pain can occur with IT band, LCL, or lateral meniscus problems. Pain behind the knee may result from a Baker cyst or musculoskeletal injury, but associated calf or leg swelling can require evaluation for a blood clot.
Pay particular attention to the symptoms occurring with the pain.
A knee that locks, repeatedly gives way, becomes substantially swollen, or remains painful despite conservative care should be evaluated.
A hot, red, severely painful swollen joint with fever, a deformed knee after trauma, neurovascular symptoms, or leg swelling accompanied by chest pain or difficulty breathing warrants urgent or emergency medical evaluation.
Medical Disclaimer
This article is for general educational purposes and does not provide an individual diagnosis or replace evaluation by a qualified healthcare professional. Knee pain can have many causes, and symptoms can overlap. Seek medical care for severe, persistent, worsening, or concerning symptoms.
References
- American Academy of Orthopaedic Surgeons. Common Knee Injuries. OrthoInfo. American Academy of Orthopaedic Surgeons. Available from: AAOS — Common Knee Injuries.
- American Academy of Orthopaedic Surgeons. Adolescent Anterior Knee Pain. OrthoInfo. American Academy of Orthopaedic Surgeons. Available from: AAOS — Anterior Knee Pain.
- National Institute for Health and Care Excellence. Gout: diagnosis and management. NICE guideline NG219. Recommendations addressing differential diagnosis of the painful, red, swollen joint and suspected septic arthritis. Available from: NICE — Gout: Diagnosis and Management.
About the author: Mark Aquino MSN, FNP-C. Mark has a Masters of Science in Nursing from West Coast University and is a board certified family nurse practitioner with over 8 years of real world experience in healthcare and currently practicing in urgent care diagnosing and prescribing treatments in California, USA. He is author of the book Physical Assessment for Nurses Simplified.