The Mayo Clinic characterises fluid build-up in the knee joints as a condition that is commonly referred to as 'water on the knee.' There are many causes, ranging from disease to injury, and the treatment will depend upon the cause. While some treatment may be complicated and require surgery, others are simple: Rest, anti-inflammatory medication, pain management drugs and cold (ice) therapy are most often the prescribed methods of treatment.
Determining the Cause
The most common reason for fluid build-up on the knee is osteoarthritis, a degenerative disease that breaks down joint cartilage. Other causes are: rheumatoid arthritis, infection, kneecap bursitis, cysts, tumours, ligament tears, meniscus tears, fractures, injury, gout and pseudo-gout. Each condition dictates a specific course of treatment.
Your doctor may perform diagnostic tests to determine the cause for the fluid build-up. An MRI will detect bone abnormalities, as well as soft-tissue damage (torn ligaments, tendons and broken-down cartilage). X-rays may be ordered if a fracture is suspected.
Arthroscopic knee surgery is both a diagnostic procedure and a treatment; an athroscope is a tool that can look inside the knee to assess damage, and at the same time, make repairs.
Other tests include aspiration---removing the fluid to evaluate for uric acid and bacteria---and blood tests. If calcium crystals are found in the fluid, your doctor will check to make sure your kidneys are functioning properly.
Treatment ranges from simple at-home remedies to complex medical procedures. They may include prescribed drug therapy, cortisone injections and the least common and most extreme treatment, knee-replacement surgery.
The most important factor in effectively treating fluid build-up on the knee is determining the cause. For example, if the fluid build-up is due to infection, it could spread to the bone; a course of antibiotics is then required to treat the infection.
Your doctor may also prescribe physiotherapy to strengthen the muscles that provide support to your knee joints.
When simple injuries and strain cause the fluid build-up, at-home remedies are often all that is needed. Avoid weight-bearing activities when the knee is swollen. Add ice packs to the knee for 15 to 20 minutes every two to four hours and elevate your knee so that it rests above the heart level.
Non-steroidal NSAID's (over-the-counter anti-inflammatory medications) are effective for pain management and they also aid in the reduction of swelling.
Wear a knee brace or knee support, such as a bandage or hard-shell brace, to keep the knee stable and reduce the pain associated with fluid build-up. Repetitive movement may aggravate an injured knee.
Once your knee begins to feel better and the swelling subsides, preventive therapy may keep the condition from recurring. If your hamstring or thigh muscles are weak, your knee absorbs most of the weight. Strengthening these muscles will help the knee absorb the shock of your weight, reducing the risk of injury and inhibiting a recurrence of the fluid build up.
If you're carrying too much weight for your body frame, a balanced diet and exercise program to reduce your weight will help keep your knees healthy and less susceptible to injury and disease.
You should always consult with your doctor to obtain a proper diagnosis before self-medicating or beginning any form of treatment.