The answer to whether COVID-19 can cause leg pain is definitively yes. This symptom can manifest during the acute phase of the infection or emerge weeks to months later as part of the post-acute sequelae of COVID-19, commonly known as Long COVID. Causes range from temporary, generalized muscle aches to serious complications involving the vascular and nervous systems. Understanding the different origins of this pain is important for managing discomfort and recognizing severe health issues.
Myalgia During Acute Infection
The most frequent cause of leg discomfort during the initial illness is myalgia, or generalized muscle aches, affecting a significant number of patients. This widespread body pain is not due to direct viral damage to muscle tissue. Instead, it is a byproduct of the body’s systemic immune response to the SARS-CoV-2 virus.
The immune system releases pro-inflammatory signaling proteins called cytokines, such as Interleukin-6 (IL-6), to fight the infection. These cytokines circulate throughout the body and activate pain receptors in muscle and joint tissues, leading to flu-like soreness and stiffness in the legs and other large muscle groups. The pain is often symmetrical, affecting both legs equally, and generally subsides as the acute infection clears and cytokine levels return to normal.
Vascular and Nerve Damage Complications
Beyond generalized muscle ache, COVID-19 can trigger localized and severe leg pain by affecting the body’s blood vessels and nerves. The SARS-CoV-2 virus induces hyperinflammation and hypercoagulability, meaning the blood is more prone to clotting. This involves the virus causing dysfunction in the endothelial cells that line the blood vessel walls, which activates the clotting cascade.
This increased clotting risk can lead to Deep Vein Thrombosis (DVT), where a blood clot forms in a deep vein, most often in the lower leg or thigh. DVT causes localized pain, typically in one leg, due to blocked blood flow. The inflammation initiated by the virus contributes to the formation of these clots, even in patients without typical risk factors for DVT.
The virus can also affect the peripheral nervous system, causing post-viral neuropathies that result in leg pain. One condition is small fiber neuropathy (SFN), which involves damage to the small nerve fibers responsible for sensing pain and temperature. This damage manifests as non-muscular pain, such as burning sensations, tingling, or numbness, often starting in the feet or distal limbs. This neurological pain is thought to be an autoimmune reaction where the immune system mistakenly attacks its own nerve tissue following the viral infection.
Persistent Leg Pain in Long COVID
Leg pain that persists for more than three months after the initial infection is considered part of Long COVID, or Post-Acute Sequelae of COVID-19 (PASC). This persistent pain is complex and results from multiple factors, extending discomfort long after the virus has been cleared. One proposed mechanism involves ongoing immune system dysregulation, where the body remains in a chronic, low-grade inflammatory state.
This chronic inflammation contributes to persistent musculoskeletal pain, including myalgia and joint pain, which may fluctuate in severity. The persistent neuropathic symptoms from small fiber neuropathy also frequently contribute to chronic leg pain in Long COVID patients. These symptoms often overlap with other post-viral syndromes, such as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), characterized by chronic fatigue and musculoskeletal issues.
Identifying Warning Signs
While most leg pain during COVID-19 is benign myalgia, the risk of Deep Vein Thrombosis (DVT) requires careful attention to specific warning signs. A blood clot in the leg is a serious medical issue because it can break loose and travel to the lungs, causing a life-threatening pulmonary embolism. Knowing how to distinguish DVT from routine muscle ache is important.
A localized, throbbing pain in one leg, usually in the calf or thigh, is a primary symptom of DVT. This pain is distinct from symmetrical myalgia and may worsen when standing or walking. The affected leg often displays visible signs, including swelling, particularly in the calf, ankle, or foot, that does not affect the other leg.
The skin over the painful area may also feel warm to the touch and appear red or darkened in color. If any of these specific, one-sided symptoms occur, particularly sudden swelling and localized pain, immediate medical evaluation is necessary to rule out DVT.