Why does rheumatoid arthritis cause joint swelling?

Rheumatoid arthritis is an inflammatory condition in which the immune system mistakenly targets tissue around joints. The lining, called the synovium, becomes irritated and produces extra fluid. The lining may also become thicker, making the joint look puffy and feel warm, tender or tight. Swelling can affect matching joints on both sides, such as the hands, wrists or feet, and may come and go during flares. Persistent inflammation can gradually limit movement and damage joint structures, so early assessment matters.

Arrange a clinical assessment if swelling lasts, returns, or affects several joints. Treatment may include prescribed medicines that calm inflammation, alongside physiotherapy or occupational therapy to maintain movement and protect function. Gentle range-of-motion exercises can help prevent stiffness, but forcing a hot, very painful joint may aggravate symptoms. Rest during a flare while continuing comfortable movement, and record which joints swell, when symptoms are worst, and whether morning stiffness accompanies them.

Seek urgent medical advice for a suddenly swollen joint with marked redness, severe pain, fever, or feeling very unwell, because infection or another urgent problem needs prompt evaluation. Contact your clinician soon if swelling is new, steadily worsening, or making ordinary tasks difficult. A clinician may examine several joints and decide whether blood tests or imaging are appropriate.

Ask which joints appear inflamed, how treatment will be monitored, and which movements are safe during a flare. You can also ask when to contact the clinic about side effects, whether a therapist can advise on hand or foot protection, and how to distinguish an inflammatory flare from an injury.