Table of ContentsView AllTable of ContentsCausesDiagnosisTreatmentPreventionFrequently Asked Questions
Table of ContentsView All
View All
Table of Contents
Causes
Diagnosis
Treatment
Prevention
Frequently Asked Questions
Water on the knee is when fluid collects around and inside the knee joint, causing pain and swelling. Also known as kneeeffusionor fluid on the knee, it can occur whenever there’s damage to the joint due to injury or underlying disease, such as arthritis.
This article explores the common causes and treatments of water on the knee and when you should get medical care.
Causes of Water on the Knee
The knee joint is asynovialjoint, meaning it is lined with a type of tissue thatproduces synovial fluid. This fluid provides nutrition to thecartilagelining the joint, lubricates it, reduces friction, and helps with joint movement.
Excess fluid around the joint can cause swelling, pain, and stiffness.
Common causes of fluid build-up on the knee include:
What Is Cartilage?Cartilage is a flexible tissue on the ends of bones that allows bones to glide smoothly over each other.
What Is Cartilage?
Cartilage is a flexible tissue on the ends of bones that allows bones to glide smoothly over each other.
Injuries
Injury is the most common cause of fluid on the knee in active, healthy people. This can include:
Arthritis and Other Inflammatory Diseases
Underlying diseases can lead to an abnormal inflammatory response that causes excess fluid on the knee as your body tries to protect your joint.
These conditions include:
Cysts
Sometimes, osteoarthritis or tears can cause cysts calledBaker’s cysts, which can cause fluid on the knee.
Baker’s cysts are fluid-filled lumps that form behind the knee when the joint is inflamed from injury or disease. Fluid flows toward the back of the knee and forms the cyst, and the cyst may contribute to swelling.
Infection
Infections can also cause fluid and pain. They can happen as a complication from surgery or inflammation, and can be due to dangerous bacteria.
Infections in the joint can be extremely painful and come on rapidly. They require prompt medical care.
When to Go to the ERIf your knee is tender, warm, red, and if you have a fever, chills, or feel ill, get immediate medical care.
When to Go to the ER
If your knee is tender, warm, red, and if you have a fever, chills, or feel ill, get immediate medical care.
To diagnose fluid on the knee, your healthcare provider will do a physical exam and check for these symptoms:
Your healthcare provider may order a procedure calledjoint aspiration, where a sample of the fluid is removed with a needle. The fluid is then analyzed forwhite blood cellsthat indicate inflammation, bacteria that reveal infection, or uric acid crystals that signal gout.
Imaging tests such as anX-rayorMRImay be ordered to help hone in on a diagnosis as well, especially if your healthcare provider suspects a tear or other injury.
Treatment for Water on the Knee
The right treatment for water on the knee depends on the cause.
In mild cases, fluid could go away on its own or with the help of some at-home treatments, such as:
If you do not notice improvement after a few days, you may need medical treatment.
Medical Treatment
If at-home treatments prove insufficient, your healthcare provider maydrain fluid from the knee(joint aspiration) to provide temporary relief.
Does Draining Fluid From Knee Hurt?Local anesthetic (one applied directly to the knee) should keep joint aspiration from being very painful. You may have some discomfort for a few days afterward, but it shouldn’t be severe.
Does Draining Fluid From Knee Hurt?
Local anesthetic (one applied directly to the knee) should keep joint aspiration from being very painful. You may have some discomfort for a few days afterward, but it shouldn’t be severe.
Injections of corticosteroidsinto the joint can help reduce pain and inflammation from injury or arthritic joint damage.
If the infection is due to drug-resistant bacteria, you may be given up to four weeks of intravenous (IV, through a vein) antibiotics.
For underlying conditions such as rheumatoid arthritis, typical treatment includesmedications that suppress an overactive immune system.
If at-home treatment methods or any prescribed medications don’t work, tell your healthcare provider right away.
Preventing Knee Effusion
Summary
Water on the knee is a painful condition that occurs when synovial fluid builds up in and around the knee joint. Injuries, infections, and medical conditions such as arthritis can cause this.
A healthcare provider can recommend treatments, such as medications and physical therapy, based on the cause of the fluid buildup.
Frequently Asked QuestionsYes, fluid on the knee is common after knee replacement surgery. Expect your healthcare provider to explore various causes, though, including rheumatoid arthritis and infection.It depends on the injury. Ice reduces inflammation, which is helpful for a recent sprain or meniscus tear.Heat relieves chronic (long-lasting) joint or muscle pain and improves flexibility.Learn MoreHow to Properly Heat or Ice Your KneeIt depends on what’s causing it. Once you have a diagnosis, ask about physical therapy so you can learn the right exercises.Common ones are stretches to improve range of motion and strength-building exercises.Yes, it can get worse without treatment. A bacterial infection can spread and cause permanent damage.An untreated meniscus tear can cause debilitating pain and loss of mobility. See a healthcare provider right away.
Yes, fluid on the knee is common after knee replacement surgery. Expect your healthcare provider to explore various causes, though, including rheumatoid arthritis and infection.
It depends on the injury. Ice reduces inflammation, which is helpful for a recent sprain or meniscus tear.Heat relieves chronic (long-lasting) joint or muscle pain and improves flexibility.Learn MoreHow to Properly Heat or Ice Your Knee
It depends on the injury. Ice reduces inflammation, which is helpful for a recent sprain or meniscus tear.Heat relieves chronic (long-lasting) joint or muscle pain and improves flexibility.
Learn MoreHow to Properly Heat or Ice Your Knee
It depends on what’s causing it. Once you have a diagnosis, ask about physical therapy so you can learn the right exercises.Common ones are stretches to improve range of motion and strength-building exercises.
Yes, it can get worse without treatment. A bacterial infection can spread and cause permanent damage.An untreated meniscus tear can cause debilitating pain and loss of mobility. See a healthcare provider right away.
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Library of Medicine.Synovial fluid analysis.Pathria MN, Chung CB, Resnick DL.Acute and stress-related injuries of bone and cartilage: Pertinent anatomy, basic biomechanics, and imaging perspective.Radiology.2016;280(1):21-38. doi:10.1148/radiol.16142305Frush TJ, Noyes FR.Baker’s cyst: Diagnostic and surgical considerations.Sports Health.2015;7(4):359-365. doi:10.1177/1941738113520130Berlinberg A, Ashbeck EL, Roemer FW, et al.Diagnostic performance of knee physical exam and participant-reported symptoms for MRI-detected effusion-synovitis among participants with early or late stage knee osteoarthritis: data from the Osteoarthritis Initiative.Osteoarthr Cartil. 2019;27(1):80-9. doi:10.1016/j.joca.2018.09.004Harvard University Medical School, Harvard Health Publishing.Persistent knee swelling in the adult.Johns Hopkins Medicine.Joint aspiration.Martin CL, Browne JA.Intra-articular corticosteroid injections for symptomatic knee osteoarthritis: What the orthopaedic provider needs to know.J Am Acad Orthop Surg. 2019;27(17):e758-e766. doi:10.5435/JAAOS-D-18-00106Tsuchie H, Miyamoto S, Seietsu S, et al.Diagnosis and treatment of joint fluid accumulation after total knee arthroplasty in rheumatoid arthrosis patients: A report of four patients.J Med Cases. 2016;7(3):90-93. doi:10.14740/jmc2429wAmerican Academy of Pediatrics: healthychildren.org.Treating sports injuries with ice and heat.Bunt CW, Jonas CE, Chang JG.Knee pain in adults and adolescents: The initial evaluation.Am Fam Physician. 2018;98(9):576-585.Jin T, Mohammad M, Pullerits R, Ali A.Bacteria and host interplay in staphylococcus aureus septic arthritis and sepsis.Pathogens. 2021;10(2):158. doi:10.3390%2Fpathogens10020158
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Library of Medicine.Synovial fluid analysis.Pathria MN, Chung CB, Resnick DL.Acute and stress-related injuries of bone and cartilage: Pertinent anatomy, basic biomechanics, and imaging perspective.Radiology.2016;280(1):21-38. doi:10.1148/radiol.16142305Frush TJ, Noyes FR.Baker’s cyst: Diagnostic and surgical considerations.Sports Health.2015;7(4):359-365. doi:10.1177/1941738113520130Berlinberg A, Ashbeck EL, Roemer FW, et al.Diagnostic performance of knee physical exam and participant-reported symptoms for MRI-detected effusion-synovitis among participants with early or late stage knee osteoarthritis: data from the Osteoarthritis Initiative.Osteoarthr Cartil. 2019;27(1):80-9. doi:10.1016/j.joca.2018.09.004Harvard University Medical School, Harvard Health Publishing.Persistent knee swelling in the adult.Johns Hopkins Medicine.Joint aspiration.Martin CL, Browne JA.Intra-articular corticosteroid injections for symptomatic knee osteoarthritis: What the orthopaedic provider needs to know.J Am Acad Orthop Surg. 2019;27(17):e758-e766. doi:10.5435/JAAOS-D-18-00106Tsuchie H, Miyamoto S, Seietsu S, et al.Diagnosis and treatment of joint fluid accumulation after total knee arthroplasty in rheumatoid arthrosis patients: A report of four patients.J Med Cases. 2016;7(3):90-93. doi:10.14740/jmc2429wAmerican Academy of Pediatrics: healthychildren.org.Treating sports injuries with ice and heat.Bunt CW, Jonas CE, Chang JG.Knee pain in adults and adolescents: The initial evaluation.Am Fam Physician. 2018;98(9):576-585.Jin T, Mohammad M, Pullerits R, Ali A.Bacteria and host interplay in staphylococcus aureus septic arthritis and sepsis.Pathogens. 2021;10(2):158. doi:10.3390%2Fpathogens10020158
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
National Library of Medicine.Synovial fluid analysis.Pathria MN, Chung CB, Resnick DL.Acute and stress-related injuries of bone and cartilage: Pertinent anatomy, basic biomechanics, and imaging perspective.Radiology.2016;280(1):21-38. doi:10.1148/radiol.16142305Frush TJ, Noyes FR.Baker’s cyst: Diagnostic and surgical considerations.Sports Health.2015;7(4):359-365. doi:10.1177/1941738113520130Berlinberg A, Ashbeck EL, Roemer FW, et al.Diagnostic performance of knee physical exam and participant-reported symptoms for MRI-detected effusion-synovitis among participants with early or late stage knee osteoarthritis: data from the Osteoarthritis Initiative.Osteoarthr Cartil. 2019;27(1):80-9. doi:10.1016/j.joca.2018.09.004Harvard University Medical School, Harvard Health Publishing.Persistent knee swelling in the adult.Johns Hopkins Medicine.Joint aspiration.Martin CL, Browne JA.Intra-articular corticosteroid injections for symptomatic knee osteoarthritis: What the orthopaedic provider needs to know.J Am Acad Orthop Surg. 2019;27(17):e758-e766. doi:10.5435/JAAOS-D-18-00106Tsuchie H, Miyamoto S, Seietsu S, et al.Diagnosis and treatment of joint fluid accumulation after total knee arthroplasty in rheumatoid arthrosis patients: A report of four patients.J Med Cases. 2016;7(3):90-93. doi:10.14740/jmc2429wAmerican Academy of Pediatrics: healthychildren.org.Treating sports injuries with ice and heat.Bunt CW, Jonas CE, Chang JG.Knee pain in adults and adolescents: The initial evaluation.Am Fam Physician. 2018;98(9):576-585.Jin T, Mohammad M, Pullerits R, Ali A.Bacteria and host interplay in staphylococcus aureus septic arthritis and sepsis.Pathogens. 2021;10(2):158. doi:10.3390%2Fpathogens10020158
National Library of Medicine.Synovial fluid analysis.
Pathria MN, Chung CB, Resnick DL.Acute and stress-related injuries of bone and cartilage: Pertinent anatomy, basic biomechanics, and imaging perspective.Radiology.2016;280(1):21-38. doi:10.1148/radiol.16142305
Frush TJ, Noyes FR.Baker’s cyst: Diagnostic and surgical considerations.Sports Health.2015;7(4):359-365. doi:10.1177/1941738113520130
Berlinberg A, Ashbeck EL, Roemer FW, et al.Diagnostic performance of knee physical exam and participant-reported symptoms for MRI-detected effusion-synovitis among participants with early or late stage knee osteoarthritis: data from the Osteoarthritis Initiative.Osteoarthr Cartil. 2019;27(1):80-9. doi:10.1016/j.joca.2018.09.004
Harvard University Medical School, Harvard Health Publishing.Persistent knee swelling in the adult.
Johns Hopkins Medicine.Joint aspiration.
Martin CL, Browne JA.Intra-articular corticosteroid injections for symptomatic knee osteoarthritis: What the orthopaedic provider needs to know.J Am Acad Orthop Surg. 2019;27(17):e758-e766. doi:10.5435/JAAOS-D-18-00106
Tsuchie H, Miyamoto S, Seietsu S, et al.Diagnosis and treatment of joint fluid accumulation after total knee arthroplasty in rheumatoid arthrosis patients: A report of four patients.J Med Cases. 2016;7(3):90-93. doi:10.14740/jmc2429w
American Academy of Pediatrics: healthychildren.org.Treating sports injuries with ice and heat.
Bunt CW, Jonas CE, Chang JG.Knee pain in adults and adolescents: The initial evaluation.Am Fam Physician. 2018;98(9):576-585.
Jin T, Mohammad M, Pullerits R, Ali A.Bacteria and host interplay in staphylococcus aureus septic arthritis and sepsis.Pathogens. 2021;10(2):158. doi:10.3390%2Fpathogens10020158
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