Water on the knee
Water on the knee is a generic term used to describe knee swelling which occurs when excess 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 when fluid collects in the bursa. This condition is known as prepatellar bursitis.

# Causes
Causes of the swelling can include arthritis, injury to the ligaments of the knee or an accident after which the brain'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;
- Osteoarthritis
- Rheumatoid Arthritis
- Infection
- Gout
- Pseudogout
- Kneecap Bursitis
- Cysts
- Tumors
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 will produce excess joint fluid.

# Signs and symptoms
Signs and symptoms of water on the knee depend on the cause of excess fluid build-up in the knee joint. These may include:

### Pain
With osteoarthritis, pain occurs when bearing weight. The pain typically subsides with rest.

### Swelling
One knee may appear larger than the other. Puffiness around the bony parts of the knee appear prominent when compared with the other knee.

### Stiffness
When the knee joint contains excess fluid, it may become difficult to bend or straighten the knee in certain cases.

### Bruising
If an individual has injured his or her knee, they 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.

# Diagnosis
Diagnostic tests include:

### X-ray
A doctor will request an X-ray to make sure the patient hasn't broken or dislocated any bones or to determine if there is arthritis present.

### MRI
Magnetic Resonance Imaging detects abnormalities of the bone or knee joint, such as a tear in the ligaments, tendons or cartilage.

### Joint aspiration
Also known as arthrocentesis, this procedure includes withdrawal of fluid from inside the knee for analysis such as cell count, culture for bacteria, and examination for crystals, such as uric acid or calcium pyrophosphate dihydrate crystals found in gout or pseudogout.

### Blood tests
If the knee is swollen, red and warm to the touch when compared to the other knee, a doctor may be concerned about inflammation due to rheumatoid arthritis or a crystalline arthritis, such as gout or pseudogout, or joint infection. Besides sending the joint fluid to a laboratory for analysis, he or she may request blood tests to determine a white blood cell count, erythrocyte sedimentation rate, and perhaps the level of C-reactive protein or uric acid.

# Treatment
Treatment of water on the knee depends on the cause of the swelling.

### Osteoarthritis
If the underlying disease happens to be Osteoarthritis, removal of the fluid from the knee joint can help relieve the pressure of joint fluid build-up. After aspirating joint fluid, the doctor may inject a corticosteroid into the joint to treat inflammation.

### Gout or pseudogout
With these two conditions, uric acid or CPPD crystals deposit in joints and may cause inflammation in the joint and surrounding soft tissues. An intra-articular (joint) corticosteroid injection, nonsteroidal anti-inflammatory drugs, or NSAIDs, (for example Motrin and Advil) or colchicine may be recommended for treatment of an acute attack of gout or pseudogout. Allopurinol or probenecid may be started after an acute attack of gout has subsided. Allopurinol decreases the body's production of uric acid in an attempt to prevent additional episodes of gout.

### Infection
The doctor will prescribe antibiotics to treat the underlying infection. The patient may need repeated aspiration of the infected joint or surgery.

### Arthroscopic knee surgery
Using an arthroscope, a surgical tool designed to look inside the knee joint, an orthopedic surgeon examines the inside of the knee joint for wear and tear. The surgeon may also repair damage inside the knee joint with this instrument.

### Joint replacement
Most people with osteoarthritis of the knee don't require surgery, but if bearing weight on the knee joint becomes intolerable, the doctor may refer a patient to an orthopedic surgeon for knee replacement.

# Prevention of Water on the Knee
To avoid water on the knee, an individual should:

### See a doctor regularly
Individuals with chronic health conditions, such as osteoarthritis, rheumatoid arthritis or gout should make regular visits to a doctor.

### Avoid activities involving physical contact with the knees
Avoiding activities that are strenuous on the knees, such as jogging, can help the prevention of water on the knee. Sports like swimming and bicycling are much less impacting on the joints.

# Self-Care
An individual with Water on the knee should take care of their knees.

### Rest
Avoiding weight bearing activities as much as possible when the knee is painful and swollen is essential.

### Ice and elevation
Cold therapy can help control pain and swelling. Application of ice to the knee for 15 to 20 minutes every two to four hours is helpful. When icing the knee, it is important to raise the knee higher than the level of the heart, using pillows for comfort.

### Pain medication
Acetaminophen (Tylenol, others) is often effective at relieving pain. NSAIDs (Advil, Motrin, others) are effective for relieving pain and inflammation.

### Muscle-toning exercises
If the thigh (quadriceps) muscle or hamstring muscles are weak, a doctor may refer a patient to a physical therapist to learn how to strengthen these muscles to better support the knee.

### Managing your weight
Losing weight will minimize the amount of weight the knees have to support when engaging in weight-bearing activities.