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Published on: 5/6/2025

When Should I Be Concerned about a Swollen Knee?

You should be concerned about a swollen knee if you have signs of infection, severe pain, or difficulty moving the joint, or if the swelling comes on suddenly after an injury.

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Explanation

When you notice a swollen knee, watch out for warning signs that might mean something serious is happening. If the knee swelling comes with fever, chills, or makes the knee feel very hot and tender, it could be a sign of infection such as septic arthritis, which needs quick medical care. Also, if you experience intense pain, sudden swelling after an injury, or if the knee feels unstable and hard to move, these can be reasons to see a doctor quickly. In children, doctors pay extra attention to these signs to make sure they are not dealing with a joint infection. In adults, sometimes knee swelling is related to long-term conditions like osteoarthritis; however, even then, if the swelling suddenly gets worse or is accompanied by new pain or redness, it should be checked out. A doctor can look at your knee, ask about any recent injuries or symptoms, and decide if tests or treatments are needed. Remember, taking care of your knee early helps prevent further problems, so if you have any of these warning signs, it’s a good idea to get help.

(References)

  • Updated 2024 Feb 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: [https://www.ncbi.nlm.nih.gov/books/NBK532279/
  • Tan JB, Sim YXA, How CH, Loh SYJ. Generalised knee swelling in adults. Singapore Med J. 2022 Apr;63(4):187-191. doi: 10.11622/smedj.2022054. PMID: 35698425; PMCID: PMC9251264.

  • Thomas CS, Schiffman CJ, Faino A, Bompadre V, Schmale GA. Diagnostic Criteria for the Painful Swollen Pediatric Knee: Distinguishing Septic Arthritis From Aseptic Effusion in a Non-Lyme Endemic Area. Front Surg. 2021 Nov 1;8:740285. doi: 10.3389/fsurg.2021.740285. PMID: 34790694; PMCID: PMC8591062.

  • Tanaka S, Nishigami T, Ohishi K, Nishikawa K, Wand BM, Stanton TR, Yamashita H, Mibu A, Tokunaga M, Yoshimoto T, Ushida T. "But it feels swollen!": the frequency and clinical characteristics of people with knee osteoarthritis who report subjective knee swelling in the absence of objective swelling. Pain Rep. 2021 Nov 8;6(4):e971. doi: 10.1097/PR9.0000000000000971. PMID: 34765853; PMCID: PMC8577815.

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