Knee pain is a common reason people go to see a doctor. One reason is that common causes of knee pain are often misunderstood. People may rest when they should actually be moving around—or ignore symptoms that need proper care. They will use ice when they should be using heat instead. They think they have arthritis when they really have syndrome. They think the pain is temporary when it is actually a meniscus that gets worse over time.. They think nothing can be done to help them when really most knee pain gets better with the right treatment for the right reason.

The knee is a joint in our body and it is the one that gets used the most. It has to handle a lot of weight and movement. When we walk it absorbs up to three times our body weight.. When we climb stairs it absorbs up to eight times our body weight. A lot of people in America over 1.9 million go to see their doctor every year because of knee pain.

Around the world over 654 million people have knee osteoarthritis. This is an increase from 1990.. The good news is that doctors can figure out what is causing the knee pain and they can treat it without surgery. The three common causes of knee pain are osteoarthritis, patellofemoral pain and meniscal tears.

This guide will explain the eight common causes of knee pain, in simple terms. It will tell you what each one feels like where it hurts, what causes it and what really works to fix it. You will get information that you can use to understand your knee pain and talk to your doctor about it.

“In clinical practice, the most important thing I do for a patient presenting with knee pain is determine whether it is structural — a ligament tear, meniscal damage, bone pathology — or functional — patellofemoral syndrome, IT band irritation, bursitis. That distinction drives everything. The 2023 JAMA review confirmed what we see every day in the clinic: the three most common causes are osteoarthritis, patellofemoral pain, and meniscal tears — and all three respond to conservative management first. Exercise, education, and load management are the evidence-based foundation for all of them. Surgery is reserved for cases that genuinely fail that conservative approach — not the starting point. Most people with knee pain get better. The key is knowing what you’re treating.”

Dr. Christina Park, DPT, OCS — Orthopedic & Pain Rehabilitation Specialist
Board-Certified Orthopedic Clinical Specialist · 14 years integrative pain rehabilitation

Where does it hurt? The fastest first step

Pain location is the single most useful initial clue in knee diagnosis — different structures occupy different regions of the knee, and pain that comes from a specific location points strongly toward specific causes. Before reading the cause sections below, identify where your pain sits. This narrows your list immediately.

Front of knee / kneecap area	Most likely causes: (Patellofemoral syndrome (runner’s knee), Patellar tendinitis (jumper’s knee), Prepatellar bursitis) — Pain under, around, or below the kneecap. Worsens going downstairs, squatting, or after prolonged sitting (“theater sign”). Very common in active people under 45.
Outside of knee (lateral)	Most likely causes: (IT band syndrome, Lateral meniscal tear, LCL sprain) — IT band pain is felt just above the bony knob on the outer knee and is sharp, often burning. Typically worsens on downhill running or repetitive knee bending.
Inside of knee (medial)	Most likely causes: (Medial meniscal tear, MCL sprain, Knee osteoarthritis (medial compartment)) — Medial OA is the most common compartment affected. Medial meniscal tears produce joint-line tenderness and often locking or clicking.
Behind the knee	Most likely causes: (Baker’s cyst, Posterior meniscal tear, Popliteal tendinopathy) — A Baker’s cyst causes a feeling of tightness or fullness behind the knee, often as a secondary consequence of another knee problem generating excess joint fluid.
Diffuse / whole joint	Most likely causes: (Osteoarthritis (all compartments), Rheumatoid arthritis, Post-ACL injury) — Widespread joint pain without a clear focal point often suggests systemic or degenerative causes rather than isolated structural damage.

Knee Osteoarthritis (KOA)

Knee osteoarthritis symptoms and treatment options affect more people than any other joint condition globally. Osteoarthritis is a disease that gets worse over time. It is marked by the breakdown of cartilage swelling in the lining hardening of the bone under the cartilage and the growth of extra bone called bone spurs. People with this condition usually have pain, stiffness and trouble moving their joints normally. The July 2026 Annals of Joint review said that than 600 million people around the world have osteoarthritis. The number of cases has gone up by 13.86% since 1990 and up to 2021.

Knee osteoarthritis usually affects the part of the knee. That is why most people with this condition feel pain on the inside of the knee especially when they are moving. Knee osteoarthritis is the common reason for knee pain in people 45 years old or older. These people often feel pain in their knee when they are active but not much in the morning. The main difference between osteoarthritis and other types of arthritis like rheumatoid arthritis is that osteoarthritis pain gets worse when you move and feels better when you rest. Rheumatoid arthritis on the hand causes longer morning stiffness and pain even when you are not moving.

Things that make it more likely for someone to get osteoarthritis include being over 45 years old being a woman ( 60% of people with osteoarthritis are women) having a body mass index over 30 having had a past injury to the knee and working in jobs that require kneeling or carrying heavy weights. A important point is that having a previous injury, to the anterior cruciate ligament (ACL) raises the chance of getting osteoarthritis for life even after surgery. This is one of the reasons to try to prevent ACL injuries in young athletes.

Characteristic Feeling

Deep aching, worse with activity, stiffness after rest

Location

Medial knee most common; can be diffuse

Who gets it

Adults 45+, women, overweight individuals, prior knee injury

Diagnosis

Clinical exam; X-ray confirms joint space narrowing

Prognosis

Progressive but manageable — surgery is last resort

Evidence-based first-line treatment

• Exercise therapy: The single most evidence-supported intervention for knee OA. Aquatic exercise, strength training (especially quadriceps), and walking all reduce pain and improve function. NICE and OARSI guidelines both recommend exercise before any other intervention
• Weight reduction: Every 1kg lost reduces knee joint load by approximately 4kg. Even 5–10% body weight reduction produces clinically meaningful pain reduction in overweight OA patients
• Patient education and self-management: The most underused free intervention. Understanding the disease reduces catastrophising and fear-avoidance, which independently amplify pain intensity
• When conservative measures fail: Intra-articular corticosteroids (short-term); hyaluronic acid (moderate OA); PRP (emerging evidence); total knee arthroplasty (end-stage disease) — a decision made only after conservative options are exhausted

Patellofemoral pain syndrome (runner’s knee)

Patellofemoral pain syndrome causes and exercises to fix it affect runners and active people of all ages and the root cause is almost never the knee itself. The front of the knee hurts when people have Patellofemoral pain syndrome. This pain is under or around the kneecap. The kneecap is a bone that floats and it is held in place by muscles. When some of these muscles in the hip are weak the knee does not move right. This makes the knee hurt when people are active.

The way to tell if someone has this problem is if their knee hurts after they sit for a time. This is called the “theater sign“. It happens when people sit with their knee bent like at a movie or at a desk. The pain goes away when they stand up and walk around. People who run can get pain in the front of the knee under or around the kneecap. This pain is worst when they are going up or down stairs or when they are running downhill.

The knee pain that runners get is usually not a problem with the knee. The knee is connected to the hip and the ankle. If the muscles in the hip are weak or if the ankle does not move right it can cause stress on the knee. To make the knee feel better people need to make their hip muscles stronger. This is especially true, for the gluteus medius muscle. When people make this muscle stronger it can really help with pain syndrome.

Evidence-based first-line treatment

• Hip strengthening — RCT evidence supports gluteus medius and hip external rotator exercises as the most effective intervention. Lateral band walks, clamshells, single-leg squats are the clinical staples
• Quadriceps strengthening — VMO (inner quad) activation via terminal knee extensions and step-downs improves patellar tracking
• Load management — reduce running volume by 30–50% during recovery; avoid downhill running and prolonged stair climbing until symptoms settle
• Patellar taping or bracing — McConnell taping reduces pain immediately and allows more effective exercise during rehab. A patellar tracking brace provides similar short-term benefit

Meniscal Tears

Meniscal tear symptoms and when surgery is needed are two of the most commonly searched knee questions and the answers often surprise people. The menisci are two C-shaped pieces of cartilage the medial menisci and the lateral menisci that act as shock absorbers between the thigh bone and the shin bone. The menisci also help to stabilise the joint and distribute the load evenly across the cartilage surfaces. When the menisci are torn they can cause problems like locking, clicking, swelling and joint-line tenderness.

Meniscal tears are one of the causes of knee pain. The meniscal tears can be diagnosed by a doctor. The McMurray test, which involves rotating and extending the knee at the time can help detect meniscal problems in about 61% of cases and is correct about 84% of the time. An MRI scan can confirm the diagnosis. Show what the tear looks like. There are two types of meniscal tears, which are different and have different effects: traumatic meniscal tears, which happen when the knee is twisted or hit suddenly often happen to younger people who are active and may need to be repaired with surgery if the tear is in the outer part of the meniscus where the blood flows. Degenerative meniscal tears happen when the menisci wear out over time in people over 40. And importantly studies have shown that these tears can be treated as well with exercise as with surgery so exercise is now the recommended first step.

The main thing to watch out for is mechanical locking. When you cannot straighten your knee all the way. This can mean that a piece of the meniscus is, out of place and you may need to see a specialist right away. If your knee is just clicking and catching, but not locking it is not as serious. Usually gets better with simple treatment. The menisci and meniscal tears are a thing to consider when you have knee pain.

Characteristic Feeling

Joint-line pain (inner or outer), locking, clicking, swelling

Traumatic tear

Sudden twist or pivot; often with audible pop and rapid swelling

Degenerative tear

Gradual onset in 40+ adults; no clear injury event

Red flag

True locking (can’t straighten knee fully) — urgent evaluation

Evidence-based first-line treatment

• Exercise therapy first for degenerative tears: Multiple RCTs including the METEOR and ESCAPE trials confirm supervised exercise matches arthroscopic surgery outcomes in degenerative tears with no locking. Surgery is not the automatic first response
• Quadriceps and hip strengthening: Reducing compressive load on the meniscus by strengthening surrounding musculature is the mechanism through which exercise provides relief
• Surgical referral when: True mechanical locking, traumatic tear in vascular zone in young active patient, or failure of minimum 3 months of supervised exercise therapy

ACL, MCL, and Ligament Tears

The signs of an ACL tear and the process of getting better usually start with the clear-cut situation in sports medicine: a quick change of direction or landing after a jump then a sound or feeling of a “pop,” sudden pain, fast swelling that happens within two to four hours and a feeling that the knee is not stable like it might give way. The ACL, which stands for cruciate ligament is the main part that stops the shinbone from sliding too far forward and keeps the knee from twisting too much. When this ligament is torn the knee no longer has the strength it needs for turning and changing directions quickly.

Women are two to eight times more likely to get an ACL injury than men. This is because of differences in body structure, muscle control and hormones. After an ACL injury there is a chance of getting knee osteoarthritis in that joint no matter if surgery is done or not. Which means that stopping these injuries from happening in the first place is really important, for young and casual athletes. MCL tears are more common and usually not as bad. Mild and moderate MCL tears can get better without surgery and don’t need the same kind of treatment as ACL tears, which in active people often need to be fixed with a reconstruction.

ACL presentation

Pop, immediate swelling, instability, unable to continue activity

MCL presentation

Inner knee pain after direct impact or valgus stress; less dramatic onset

Swelling timing

ACL: rapid (2–4 hrs); meniscal: slower (12–24 hrs)

Long-term risk

Significantly increased OA risk regardless of surgical treatment

Evidence-based first-line treatment

• Immediate PRICE protocol: Protection, Rest, Ice, Compression, Elevation. RICE within first 72 hours reduces swelling and secondary damage. Seek orthopedic evaluation within 1–2 weeks
• ACL reconstruction vs conservative: Surgical reconstruction is recommended for active patients wanting to return to pivoting sports; evidence supports either approach for less active individuals. A 9–12 month rehabilitation programme precedes return to sport regardless of path
• MCL tears – Grade I/II: Conservative management with bracing and PT. Grade III: orthopedic evaluation for potential surgical repair

Patellar tendinitis (jumper’s knee)

Exercises that work start with finding the exact spot where the problem is, Patellar tendinitis, which is also known as tendinopathy when its long-term is when the patellar tendon gets inflamed and has tiny tears. This is the rope that connects the kneecap, which is called the patella to the shinbone, which is called the tibia. The pain is usually at the part of the patella, which is the tip of the kneecap. This is different from syndrome, which is pain all around the kneecap and not just at the bottom edge.

This condition is called “jumpers knee” because jumping a lot puts a lot of stress on the tendon. It’s very common in sports, like basketball, volleyball and track and field.. It also happens to runners and cyclists because their knees get used a lot. The tendon becomes sensitive and hurts especially when you first start moving. The pain usually goes away after you warm up. This is a sign of tendinopathy. The best treatment that has been proven to work for tendinopathy is eccentric loading. This means doing slow resistance training or using the decline squat method. These exercises help the tendon change its structure, which makes the pain less and helps the knee handle stress over 12 weeks.

Location

Precisely at the inferior pole of the kneecap — below the kneecap

Pattern

Start-up pain that eases with warm-up; worsens after loading

Who gets it

Jumping athletes, basketball, volleyball, runners

Best treatment

Heavy slow resistance / eccentric loading — 12-week programme

Evidence-based first-line treatment

• Eccentric decline squat programme: The single most evidence-supported intervention. 3 sets of 15 reps on a 25° decline board, twice daily, 12 weeks. Painful to start — that is expected and appropriate for tendon remodelling
• Heavy slow resistance (HSR): A lower-pain alternative that produces equivalent outcomes to eccentric loading in RCTs. Leg press, leg extension, hack squat at 70–80% of maximum, 3×15 working toward 4×6 over 12 weeks
• Load management: Reduce jumping volume during rehabilitation; isometric exercises (wall sits, leg press holds) provide immediate analgesic effect for acute pain relief during training

Iliotibial Band Syndrome (ITBS)

IT band syndrome causes and how to treat iliotibial band pain affect runners almost exclusively, it is one of the two most common running-related knee injuries alongside patellofemoral syndrome, and the most common cause of lateral (outer) knee pain in runners. The IT band is a strong band that goes from the hip down the outside of the thigh to just below the knee. You feel IT band pain above the bony part on the outside of the knee. It hurts more when you run downhill. This is because your knee is a bit bent and the IT band is pressing on the fat underneath it.

People used to think that the IT band was just too tight.. Now we know that IT band syndrome is actually a problem with the IT band pressing on the fat underneath it. This makes the fat get inflamed and hurt. Rolling the IT band with a foam roller does not make it feel better. This is because the IT band cannot really be stretched.

To make the pain go away you have to fix the problem. This is usually because the muscles, in your hip are not strong enough. The gluteus medius muscle is especially important. If it is weak your knee will move much to the side and the IT band will get pressed on more. Another problem is if you start running much too fast. Your body needs time to get used to it. If you do not give it time you will get hurt. Effective treatment targets the hip abductor weakness and the sudden training load increases that cause IT band compression and IT band pain.

Location

Just above the bony outer knob of the knee (lateral femoral condyle)

Characteristic

Sharp or burning pain; worse on downhill running; may stop you mid-run

Root cause

Hip abductor weakness + sudden training volume increase

Not effective

Prolonged foam rolling of the IT band itself

Evidence-based first-line treatment

• Hip abductor strengthening: Gluteus medius targeted exercises (clamshells, lateral band walks, single-leg exercises) address the primary biomechanical driver. 6–8 weeks of progressive hip strengthening produces the strongest evidence-based outcomes
• Running load reduction + graded return: Reduce mileage by 30–50%, eliminate downhill running during recovery. Return graded over 4–6 weeks once symptom-free on flat terrain
• Gait retraining: Increasing step rate by 5–10% reduces IT band compression at the critical 30° flexion position. A physiotherapist can guide this effectively in 4–6 sessions

Knee Bursitis (Prepatellar and Pes Anserine)

Knee bursitis symptoms treatment and recovery differ depending on which bursa is inflamed. The knee has approximately 11 bursae, small fluid-filled sacs that reduce friction between structures. The prepatellar bursa and the pes anserine bursa are the two bursae that cause the problems. The prepatellar bursa is located in front of the kneecap. This is what people call “housemaids knee” because it happens when you kneel for a time. The pes anserine bursa is on the side of the knee about two inches below the joint line. This one is more common in people who run a lot and in people who’re overweight and have OA.

When you have bursitis you can see a big swelling in front of the kneecap. It is really obvious especially if you compare it to the knee. The skin on top of the swelling may be red. Feel warm. But it is not the knee joint that’s swollen it is the prepatellar bursa. The prepatellar bursa is between the skin and the bone not inside the joint.

Pes anserine bursitis is different. It causes pain on the side of the knee below the joint line. This pain can be hard to diagnose because it feels like OA or a problem with the meniscus.. If you press on the spot you can feel that the pain is below the joint line on the inner shin, not right, at the joint line.

Prepatellar

Visible swelling in front of kneecap; from kneeling; can become infected

Pes anserine

Pain 2 inches below inner joint line; runners + OA patients

Red flag

Warmth, redness, fever — possible septic bursitis requiring urgent drainage

Usual resolution

4–8 weeks with conservative management

Evidence-based first-line treatment

• Activity modification: Avoid the specific activity causing repeated friction or impact. Kneeling pads for occupational bursitis; running modification for pes anserine
• Ice and NSAIDs: Reduce acute inflammation. 15–20 minutes ice application several times daily during flare
• Corticosteroid injection: When conservative measures fail, a single well-placed corticosteroid injection produces rapid relief in most cases. For septic (infected) bursitis, aspiration and antibiotics are required urgently

Rheumatoid Arthritis and Inflammatory Arthropathies

Rheumatoid arthritis knee pain vs osteoarthritis how to tell the difference is one of the most clinically important distinctions in all of joint medicine and the features that separate them are consistent and recognisable. Other causes of knee pain include rheumatoid arthritis, crystal-related conditions and spondylo-arthropathies all of which need to be considered when trying to figure out the cause of the pain. These are different from the common type of knee pain caused by wear and tear called osteoarthritis. The signs that point to a joint disease are:

Stiffness in the morning that lasts more than 30 minutes. Osteoarthritis causes stiffness that’s usually less than 30 minutes and goes away quickly when moving around. The joint problem affects both sides of the body like both knees, both wrists and both small joints in the hands. Osteoarthritis usually affects one side more than the other. Is linked to use. People with joint disease may feel tired have a low-grade fever and feel generally unwell. Pain that wakes the person up during the night. Osteoarthritis pain usually gets better with rest. Inflammatory arthritis can get worse at night. Blood tests may show levels of inflammation like ESR and CRP. Also the blood may test positive for rheumatoid factor or anti-CCP antibodies. Crystal-related conditions like gout and pseudogout can cause sudden and severe swelling, in the knee that happens quickly. Gout often affects the toe but can also affect the knee. Pseudogout is commonly seen in the knee joint in older adults.

Morning stiffness

30+ minutes (vs under 30 min in OA)

Pattern

Symmetrical bilateral joints (vs asymmetric load-related in OA)

Gout/pseudogout

Acute dramatic swelling over hours; extremely painful

First step

Rheumatologist referral for diagnosis and DMARD therapy

Evidence-based first-line treatment

• Rheumatologist referral: RA requires disease-modifying antirheumatic drugs (DMARDs). Early initiation of methotrexate or biologic therapy prevents joint destruction that OA management cannot address
• Exercise and physiotherapy: Evidence supports exercise for RA management alongside pharmacological treatment; low-impact aquatic exercise and range-of-motion work maintain function
• For gout: Colchicine or NSAIDs for acute flares; uric acid-lowering therapy (allopurinol) for prevention; dietary modification (reduce red meat, alcohol, fructose)

Red flags: when to see a doctor without delay

• True mechanical locking: Inability to fully straighten the knee — suggests a displaced meniscal fragment requiring urgent orthopedic assessment
• Rapid swelling within 2–4 hours of injury: Haemarthrosis (blood in the joint) occurs with ACL tears and significant fractures; MRI evaluation urgent
• Knee bursitis with fever, redness and warmth: Signs of septic (infected) bursitis requiring same-day medical evaluation and likely antibiotics or aspiration
• Severe sudden onset joint swelling with extreme pain: Possible gout, pseudogout, or septic arthritis. Septic arthritis is a medical emergency requiring hospitalisation
• Knee pain with visual deformity or inability to bear weight: Possible fracture; seek emergency evaluation
• Night pain that wakes you from sleep combined with systemic symptoms: Could indicate inflammatory arthritis or, rarely, bone pathology requiring investigation

Prevention: what actually protects your knees long term

• Strengthen Your Hips First: Weak hip abductors and external rotators are the upstream cause of most running-related knee injuries, PFPS, IT band, and patellofemoral stress. Gluteus medius strengthening is the single highest-leverage preventive exercise for all knee overuse conditions.
• Manage Your Body Weight: Every kilogram of body weight generates approximately 4kg of force at the knee joint with each step. Weight management is the most modifiable risk factor for knee OA development and progression, a 5% weight reduction produces clinically meaningful pain reduction.
• \Increase Training Load Gradually: The majority of overuse knee injuries (PFPS, ITBS, patellar tendinopathy) follow a period of sudden training increase. The 10% rule increasing weekly volume by no more than 10% per week, is the most practical injury prevention strategy for recreational athletes.
• Stay Active Consistently: Contrary to popular belief, regular moderate exercise protects cartilage rather than wearing it out. Cartilage receives nutrients via compression and decompression during movement prolonged inactivity starves cartilage and accelerates degeneration in OA.
• Address Ankle Mobility: Limited ankle dorsiflexion forces compensatory knee valgus during squatting and running increasing patellofemoral stress with every rep or stride. Daily ankle mobility work (heel drops, ankle circles) is a surprisingly high-leverage knee injury preventive intervention.
• Treat Injuries Fully before Returning: Premature return to sport after ligament injuries and meniscal tears is the primary driver of re-injury and accelerated OA development. Completing the full rehabilitation timeline not just becoming pain-free — is the correct return-to-sport criterion.

The bottom line — your knee can almost certainly get better

The important message from the 2023 JAMA review and every guideline that came after it is this: for the three most common causes of knee pain. Osteoarthritis, patellofemoral syndrome and meniscal tears. The first choice of treatment is exercise, education and self-management. Not surgery. Not long periods of rest. Not waiting to see if it goes away on its own. Planned and suitable movement is the treatment based on research that gives the long-lasting results for every major knee pain condition.

Understanding the cause of the knee pain is the step in knowing which exercise is right which movements to limit for now and when to get help from a specialist. Pain in the front of the knee under the kneecap that gets worse when going down stairs is a sign of patellofemoral syndrome and the solution is to strengthen the hips.

Sharp pain on the outside of the knee that stops a runner at mile three suggests IT band syndrome.. The fix is to strengthen the glute med. A deep aching on the inside of the knee in a 55-year-old after walking suggests medial compartment OA. And the research shows that a mix of strengthening the quadriceps and managing weight is the way to go.

If your knee pain has lasted than two weeks is stopping you from doing normal things or happened after a clear injury see a physiotherapist or an orthopedic doctor. A proper diagnosis in one visit can guide the six weeks of self-management much better, than spending weeks trying to figure it out on your own. Most knee pain can get better. The main thing is to match the treatment to the cause.

Research Citation

· Skou ST, Roos EM, et al. Evaluation and Treatment of Knee Pain: A Review. JAMA. 2023;330(16):1568-1580. PMID: 37874571 ↗
· Lv J, Hu C, Zhang H, et al. A narrative review of clinical research on knee osteoarthritis in 2025. Annals of Joint. 2026;11:39. Published July 15, 2026. aoj.amegroups.org ↗
· Vanneste M, et al. Chronic knee pain: a comprehensive narrative review. Pain Practice. 2024. Wiley Online Library ↗
· Berteau JP. Knee Pain from Osteoarthritis: Pathogenesis, Risk Factors, and Recent Evidence on Physical Therapy Interventions. J Clin Med. 2022. PMC9224572 ↗
· UpToDate. Approach to the adult with knee pain likely of musculoskeletal origin. Literature current through May 2026, updated Oct 2025: uptodate.com ↗

· Cleveland Clinic. Knee Pain: What It Is, Causes, Treatment & Relief. Medically reviewed July 20, 2025: clevelandclinic.org ↗
· QC Kinetix. Knee Pain Statistics: 2025 Facts and Treatment Trends. April 21, 2026: qckinetix.com ↗
· HSS Hospital for Special Surgery. Knee Pain Conditions, Causes, Symptoms, Treatments. January 2025: hss.edu ↗
· Swift PT & Performance. Knee Pain When Running: Causes, Treatment, and How to Get Back to Running Pain-Free. June 25, 2026: swiftptandperformance.com ↗
· WebMD. Knee Pain and Injuries: Causes, Treatment, and Prevention. Medically reviewed by Tyler Wheeler MD, March 28, 2026: webmd.com ↗
· Joint Relief Institute. New Knee Treatments 2025–2026: Latest Innovations. January 26, 2026: jointreliefinstitute.com ↗