Knee effusion
| Knee effusion | |
|---|---|
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| A traumatic right knee effusion; note the swelling lateral to the kneecap as marked by the arrow | |
| Classification and external resources | |
| ICD-10 | M25.4 |
| ICD-9-CM | 719.0 |
| DiseasesDB | 15237 |
Knee effusion or swelling of the knee (colloquially known as water on the knee) occurs when excess synovial fluid accumulates in or around the knee joint. There are many common causes for the swelling, including arthritis, injury to the ligaments or meniscus, or fluid collecting in the bursa, a condition known as prepatellar bursitis.
Signs and symptoms of water on the knee depend on the cause of excess synovial fluid build-up in the knee joint. These may include:
Osteoarthritis knee pain usually occurs while the joint is bearing weight, so the pain typically subsides with rest; some patients suffer severe pain, while others report no discomfort. Even if one knee is much larger than the other, pain is not guaranteed.
One knee may appear larger than the other. Puffiness around the bony parts of the knee appear prominent when compared with the other knee.
When the knee joint contains excess fluid, it may become difficult or painful to bend or straighten. Fluid may also show under the knee when straightened. Icing may help to decrease swelling. Heat may help relax the muscles of the knee.
If an individual has injured his or her knee, he or she may note bruising on the front, sides or rear of the knee. Bearing weight on the knee joint may be impossible and the pain unbearable.
Causes of the swelling can include arthritis, injury to the ligaments of the knee, or an accident after which the body's natural reaction is to surround the knee with a protective fluid. There could also be an underlying disease or condition. The type of fluid that accumulates around the knee depends on the underlying disease, condition or type of traumatic injury that caused the excess fluid. The swelling can, in most cases, be easily cured.
Underlying diseases may include
Having osteoarthritis or engaging in high-risk sports that involve rapid cut-and-run movements of the knee — football or tennis, for example — means an individual is more likely to develop water on the knee.
In overweight or obese individuals the body places more weight on the knee joint. This causes more wear in the joint. Over time, the body may produce excess joint fluid.
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