Healthy knees are essential for physical health and mobility. Poor knee health can lead to decreased mobility and functional limitations, which leads to diminished quality of life. Without healthy knees, everyday activities like climbing stairs, standing, and even sitting become difficult. Additionally, weak knees can increase the risk of knee and joint injuries such as ACL tears and sprains.
But things can go wrong with knees too. What does it mean if you have water on your knee? You may have heard this expression and wondered what it means. Or you may have been unfortunate enough to be told you have water on your own knee. But what does that mean?
What Is Water on the Knee?
Water on the knee is a term used to describe fluid accumulation around the knee joint from any cause. The medical term is knee effusion. It’s not a specific medical condition in and of itself. Fluid or water on the knee can come from a variety of causes – some of which are serious. Here are some of the most common reasons you can have water on your knee.
Water on the Knee Can Be Caused by a Knee Injury
One way to end up with a knee effusion is to sustain a knee injury to a ligament. A ligament is a band of tissue that connects two bones and helps to stabilize and support the joint. In the knee joint, ligaments are critical for providing stability to the joint and helping to control the range of motion. They provide stability to the knee joint by helping control the back-and-forth motion of the knee, as well as the inward and outward motion of the knee.
If you tear the ligaments or cartilage in your knee while playing sports, especially when changing directions suddenly, you may get sudden knee swelling and accumulation of fluid in the knee joint. If you tear a ligament, the swelling usually appears within six hours of the injury, and you may hear an audible “pop” when the ligament tears – followed by substantial pain and difficulty bearing weight on the knee. In this case, water on the knee comes from fluid leaking from damaged blood vessels. If you suspect a ligament injury, it needs evaluation and you shouldn’t bear weight on the leg until a healthcare professional looks at it.
Torn Cartilage Can Also Cause Water on the Knee
Another cause of knee effusion is a cartilage tear. Cartilage is a firm yet flexible connective tissue found in the knee joint. It acts as a shock absorber and functions to reduce friction within the knee joint. It is composed of proteoglycans, collagen fibers, and other molecules, that are highly elastic. Cartilage provides cushioning to the knee joint and helps absorb the impact of physical activities such as running and jumping. Without cartilage, bones would rub together, causing pain and possible joint damage.
With a cartilage or meniscus tear, you may hear a pop, especially if it occurs due to injury, but, in other cases, the symptoms are more gradual with progressively worsening knee pain and swelling. The knee may “lock up”, making it difficult to straighten out the leg completely. It may be difficult to squat or kneel with a torn meniscus. You can also develop water on the knee due to inflammation and accumulation of fluid within the knee.
Water on Your Knee Not Due to Injury
There are other knee problems that can cause water on your knee in the absence of injury. The most frequent cause of fluid not caused by injury is osteoarthritis. Osteoarthritis of the knee is a degenerative joint condition that is caused by the breakdown of the cartilage that cushions the joints. This breakdown of cartilage can lead to chronic pain, stiffness, swelling, and decreased range of motion. It is most common in adults over the age of 50 and occurs more frequently in women than in men.
With this very common cause of knee pain and swelling, the knee feels stiff and painful, especially in the morning. Other forms of arthritis like rheumatoid arthritis can cause painfully swollen knees too.
Bursitis Can Cause Water on the Knee Too
Another frequent cause of water on the knee is bursitis, which often affects carpenters and people who spend time on their knees. Bursa are thin sacs filled with lubricating fluid that is nestled between a bone and a tendon or muscle. The bursa helps to cushion the space between bone and tendon and reduce friction as the two structures glide past one another.
Unfortunately, bursal spaces can become inflamed. When they do, fluid accumulates around the knee, which is usually worse when kneeling. If bursitis of the knee doesn’t resolve, a doctor can remove the fluid using a needle and a syringe in their office.
Other less common causes of water on your knee include gout, tumors, cysts, and a condition called pseudogout.
How Do You Treat Knee Effusion?
The best treatment for knee effusion will depend on the underlying cause. Most therapists recommend rest, ice, compression, and elevation (RICE) to reduce swelling and manage pain. Physical therapy, including stretching, strengthening, and range of motion exercises, can also help to reduce pain and improve function.
Some providers prescribe medications such as non-steroidal anti-inflammatory drugs (NSAIDs) or corticosteroids for severe cases to reduce pain and relieve inflammation. Proper bracing and the use of assistive devices can help to improve alignment, reduce stress on the joint, and provide additional support. In some cases, surgery may be necessary to correct the underlying issue. It is important to consult with a medical professional to determine the best course of treatment for knee effusion.
If You Have a Knee Effusion, Get It Evaluated
If you have water on your knee, see a doctor, especially if the swelling occurs while playing sports. If you suspect a torn meniscus or ligament in the knee, keep the knee elevated, apply ice, and see your doctor right away. If there’s a potential for a torn ligament, don’t bear weight on the leg to avoid further damage. If it’s a complete tear, the knee may be unstable, and it may be almost impossible to bear weight on the knee or walk. That’s a sign that you need immediate evaluation.
References:
- “Knee Injury – Soft Tissue”
- “Knee Effusion – StatPearls – NCBI Bookshelf.” 04 May. 2022, https://www.ncbi.nlm.nih.gov/books/NBK532279/.
- “Osteoarthritis of the Knee – Arthritis Foundation.” https://www.arthritis.org/diseases/more-about/osteoarthritis-of-the-knee.
- “Knee Effusion: Cause, Symptoms, Physiotherapy Treatment & Exercise.” 26 Mar. 2019, https://samarpanphysioclinic.com/knee-effusion/.
- “Knee Effusion Causes, Symptoms, and Treatments in Fairfield | OSGPC.” 13 Feb. 2017, https://www.osgpc.com/knee-effusion-causes-symptoms-treatments/.
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