COVID-19, primarily known as a respiratory illness, presents with a wide array of symptoms beyond the lungs. Many individuals report joint or muscle pain, raising questions about a connection to conditions like knee pain. Understanding this relationship clarifies the virus’s diverse impacts.
Is Knee Pain a Symptom of COVID-19?
Musculoskeletal pain, including joint and muscle pain, is a reported symptom of COVID-19. Studies indicate that approximately 15% of infected individuals experience joint pain during the acute phase. This discomfort can appear with or without typical respiratory symptoms, showing a varied presentation.
Knee pain is frequently identified among affected joints in COVID-19 cases. While not the most common symptom, joint pain can be noticeable and emerge suddenly. It can also persist as a concern for individuals experiencing post-acute COVID-19 conditions, often called Long COVID.
How COVID-19 Might Cause Knee Pain
COVID-19 can cause knee pain through complex mechanisms involving the body’s immune response. The infection triggers widespread systemic inflammation as the immune system fights the virus. This process affects various tissues, including joints. Pro-inflammatory molecules like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) are elevated during COVID-19 and contribute to this inflammation.
In some cases, the immune system might overreact, leading to a hyperinflammatory “cytokine storm.” This excessive response can damage tissues, including cartilage, a key component of joint health. The cytokine imbalance in COVID-19 shares similarities with certain inflammatory rheumatic diseases.
Less commonly, direct viral effects on joint tissues have been explored. Viral nucleic acids have been sporadically detected in joint fluid, suggesting a direct impact. Research indicates the SARS-CoV-2 spike protein alone can trigger joint pain and cellular aging in cartilage cells. The virus may also directly affect blood vessels and tissues, causing inflammation and damage similar to traditional rheumatic conditions.
Persistent joint pain, including knee pain, is a recognized symptom of Long COVID. This post-viral syndrome can cause symptoms to last for weeks, months, or even years after the initial infection. Prolonged inflammation or immune dysregulation associated with Long COVID can contribute to new-onset inflammatory arthritis or conditions like reactive arthritis, where joint pain and swelling occur after an infection.
Other Common Causes of Knee Pain
Knee pain has numerous origins, not all connected to COVID-19. Injuries are a frequent cause, ranging from sprains and strains to meniscus tears, ligament injuries (such as ACL, PCL, or MCL), fractures, or dislocations. These can result from sudden impacts, twisting, or falls.
Various forms of arthritis are also common sources of chronic knee pain. Osteoarthritis, often from wear and tear, involves cartilage breakdown in the joint. Rheumatoid arthritis, an autoimmune condition, can affect the knees, causing inflammation and pain. Gout, characterized by uric acid crystal buildup, is another potential cause.
Overuse conditions can lead to knee discomfort, particularly in active individuals. Examples include patellofemoral pain syndrome (runner’s knee) and tendinitis (inflammation of tendons). Bursitis, inflammation of fluid-filled sacs cushioning the knee joint, can also cause pain. Other viral or bacterial infections can trigger joint pain, known as viral arthritis.
When to Consult a Healthcare Professional
Consult a healthcare professional if knee pain is persistent, worsens, or significantly interferes with daily activities or sleep. This is important if the pain is severe or accompanied by other concerning symptoms.
Seek medical attention if the knee exhibits severe swelling, redness, warmth, or tenderness, or if there is an inability to bear weight. A bent or deformed joint appearance, or a popping sound at injury, also warrants prompt evaluation. If knee pain occurs alongside a fever or other signs of illness, a medical assessment can help determine an underlying infection or other condition.