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Swollen knee joints (swollen knee)
Last reviewed: 06.07.2025
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Swelling of the knee joints may be a manifestation of arthritis. Osteoarthritis tends to affect the posterior aspect of the patella and the medial aspect of the knee, often resulting in a varus deformity, usually managed with NSAIDs and weight loss measures; sometimes with local steroid injections. Surgery may also be necessary. Varus deformity can be corrected with osteotomy. The knee joint may be affected by rheumatoid arthritis, gout, and septic arthritis.
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Other Causes of Swollen Knees
Meniscus cysts
In this condition, the degree of swelling in the knee joint varies greatly, but the pain is localized above the joint area. Lateral cysts are more common than medial cysts. The swelling is most noticeable when the knee joint is bent at 60-70°, and is least noticeable when fully bent. The meniscus often tears in an unusual medial direction, which can cause "clicks" in the knee joint and relaxation of its ligaments. The pain goes away after the cyst and damaged meniscus are removed. Ligament tears, meniscus lesions, and patellar displacement are some of the main causes of knee joint swelling.
Osteochondritis dissecans
The essence of the disease is local necrosis of the articular cartilage and underlying bone, which leads to the formation of free bodies in the joint cavity, separating from the surrounding bone tissue. The cause is unknown. Most often, the medial condyle of the femur is affected. The disease usually begins in adolescence and youth, and after physical exertion, pain occurs in the knee joint, which sometimes swells. Joint blockade also occurs. X-rays reveal defects on the articular surface. Since spontaneous recovery may occur, there is no rush to treat, especially in the early stages of the disease. The affected area can be surgically removed (if it has not yet been torn off in this place), which will prevent its tearing off, or it can be fixed in place with a pin. This condition predisposes to the development of arthritis.
Loose bodies (joint mice) in the knee joint cavity
Their presence causes blocking of the knee joint (in this case, all movements in the joint are impaired, unlike partial blockade that occurs with a meniscus rupture, when only extension is sharply limited) with subsequent swelling due to the accumulation of effusion.
Causes: osteochondritis dissecans (there are up to 3 free bodies in the joint cavity), osteoarthritis (no more than 10 free bodies), comminuted fractures of the articular surface (no more than 3 free bodies) or synovial chondromatosis (more than 50 free bodies). If the presence of free bodies (joint mice, or arthremphytes) in the joint cavity causes its blockade, they should be removed. This can be done using arthroscopy.
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Bursitis
There are 16 synovial sacs, or bursae, around the knee joint. The most commonly affected is the prepatellar bursa (maid's knee). This is characterized by swelling over the anterior inferior surface of the patella, caused by inflammation of the bursa and accumulation of fluid in it due to increased friction (work performed while kneeling). If the inferior bursa of the patella becomes inflamed, it is called "vicar's knee" (clergy also often kneel, but in a more upright position). The semimembranous bursa in the popliteal fossa can also become inflamed (this is a popliteal fossa cyst, which differs from a Baker's cyst, located in the same place and representing a hernial protrusion of synovium from the knee joint cavity). The prepatellar bursa can be aspirated, injected with hydrocortisone to reduce its recurrence, and finally, if persistent, surgical excision is necessary. Diagnostic aspiration of the bursa can differentiate aseptic bursitis, which results from excessive friction, from infectious, often purulent bursitis, which requires surgical drainage and antibiotics such as flucloxacillin 250 mg orally every 6 hours.
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