How common is knee swelling in septic arthritis?

Septic arthritis is an infection inside a joint. In the knee, inflammation can produce swelling, warmth, marked tenderness, and difficulty moving the leg. The joint may become painful over a short time, and fever, chills, or feeling unwell can occur, although not everyone has every symptom.

Knee swelling has many possible causes, so swelling alone cannot confirm infection. The combination of rapid worsening, warmth, severe pain, reduced movement, or general illness makes urgent evaluation especially important. A healthcare professional may examine the knee and arrange tests, which can include taking a sample of joint fluid.

Do not massage, puncture, or try to drain a swollen knee yourself. Limit weight-bearing if walking is very painful and arrange same-day medical advice when infection is a concern. Note when the swelling began, whether you have fever, and any recent wound, injection, surgery, or illness to tell the clinician.

Treatment depends on the cause and may require hospital care, antibiotics, and drainage of infected fluid. Do not delay assessment while waiting to see whether rest or home measures settle the swelling.

Seek urgent care now for a hot, swollen, very painful knee, especially with fever, chills, confusion, weakness, or difficulty standing. Immediate attention is also needed if symptoms are worsening quickly or you have a weakened immune system, recent joint procedure, or open wound near the knee.

Ask whether the knee needs urgent testing for infection, whether joint-fluid sampling is appropriate, and which medicines or activities to avoid before assessment. Explain the timing of swelling, your temperature if checked, and any recent injury, procedure, skin infection, or new illness.