What Is a Joint Effusion of the Knee?

A knee effusion, more commonly called water on the knee, occurs when excess fluid accumulates around the knee joint, according to Medical News Today. This swelling has several causes including arthritis, injury to ligaments and fluid in the bursa. Symptoms of knee effusion include pain when bearing weight, appearance of one knee larger than the other, difficulty straightening the joint and bruising.

Initial assessments done by an orthopaedic doctor involve careful examination of the affected knee as compared to a patient's healthy knee. American Family Physician reveals doctors ascertain the normal range of motion for the knee and palpitate the joint to feel for swelling.

Mayo Clinic explains that a doctor may obtain a fluid sample from the knee to determine if an infection, disease or injury causes the inflammation and fluid buildup. Medical News Today explains joint aspiration retrieves fluid for cell counts, bacteria cultures and examinations for salt crystals possibly found in the knee. Uric acid and calcium pyrophosphate dihydrate crystals associated with gout may be present in an effused knee.

Treatment options vary from medications to surgery, according to Mayo Clinic. A doctor may prescribe medications to alleviate pain, antibiotics to kill bacteria and corticosteroid injections to quickly reduce swelling. Stronger treatment options include joint aspiration to relieve pressure, arthroscopic surgery to repair minor damage and joint replacement if walking on the knee is too unbearable during everyday activities.