Swollen knuckles are frequently caused by different forms of arthritis, reports Healthline. Other causes include bone fractures, torn ligaments, torn tendons, ankylosing spondylitis and systemic lupus erythematosus.
There are several forms of arthritis. The most common is osteoarthritis, which is the natural degeneration of joint cartilage, states Healthline. Rheumatoid arthritis, an autoimmune disease, occurs when the body mistakenly attacks healthy tissue. Gout occurs when uric acid, a by-product of digesting certain foods, builds up in the joints. Psoriatic arthritis accompanies the skin condition known as psoriasis. Bacterial or fungal infections can lead to septic arthritis.
Ankylosing spondylitis involves severe inflammation of the vertebrae that, in the worst cases, leads to chronic pain and disability, according to WebMD. Systemic lupus erythematosus is another autoimmune disease that causes joint swelling. It is often accompanied by a butterfly rash over the cheeks and bridge of the nose.