A burning sensation in the knee is a common complaint that limits mobility and disrupts daily life. This localized discomfort signals irritation to the nerves or tissues surrounding the joint. Understanding the mechanisms and conditions that trigger this sensation is the first step toward addressing the issue. The underlying reasons are generally categorized as either direct joint inflammation or issues stemming from nerve pathway irritation.
The Science of Nerve Irritation
The distinct feeling of heat or burning is directly linked to how the body’s pain receptors communicate with the brain. Specialized sensory nerve endings, known as nociceptors, detect potentially damaging stimuli like pressure, heat, or chemical irritants. The slower, burning sensation is primarily carried by unmyelinated C-fibers, which conduct impulses slowly. When tissue damage or inflammation occurs in the knee, it releases chemical mediators like bradykinin and prostaglandins. These substances sensitize the C-fibers, causing them to fire signals that the brain interprets as a burning sensation, even without external heat.
Common Causes Related to Joint Inflammation and Overuse
Many instances of burning knee pain result from mechanical stress and inflammation within the joint or surrounding structures. One frequent cause is Patellofemoral Pain Syndrome (PFPS), often called “Runner’s Knee.” The cartilage beneath the kneecap becomes irritated due to repetitive motion or muscle imbalance, leading to burning pain primarily felt at the front of the knee, especially when climbing stairs or squatting.
Inflammation of the fluid-filled sacs that cushion the joint, known as bursitis, is another common culprit. When a bursa becomes inflamed, such as the prepatellar bursa from excessive kneeling, it swells and creates localized pressure. This pressure and inflammatory chemicals irritate surrounding nerve endings, causing a distinct burning feeling.
Tendinitis, involving the patellar or quadriceps tendon, includes inflammation and micro-tears in the tendons connecting muscle to bone. This overuse condition results in front-of-the-knee burning pain that worsens with activity.
Conditions involving joint deterioration, such as osteoarthritis, cause a burning sensation as the protective cartilage wears away. The resulting bone-on-bone friction and chronic inflammation irritate the joint’s sensory nerves. Iliotibial Band Syndrome (ITBS), common in runners, involves friction and inflammation of the thick band of tissue running along the outside of the thigh and knee. This mechanical irritation causes burning pain specifically on the outer side of the knee joint.
Specific Conditions Involving Nerve Compression
A burning knee sensation can originate from issues separate from the joint, often involving peripheral nerve compression or damage. Peripheral neuropathy is a type of nerve damage that frequently causes a persistent burning or tingling sensation in the extremities. This sensation often starts in the feet and can progress up into the knee area. This condition is commonly associated with systemic diseases like diabetes, which affect the function and blood supply of peripheral nerves.
Referred pain from the lower spine, known as sciatica, can also manifest as burning discomfort around the knee. Sciatica occurs when the sciatic nerve is irritated or compressed in the lower back, but the sensation travels down its path, which can include the thigh and knee.
Another localized neurological issue is the entrapment of the common peroneal nerve, a branch of the sciatic nerve near the knee. This nerve is vulnerable to compression from external factors like prolonged leg crossing or internal issues such as swelling. Damage to the peroneal nerve can result in burning pain, numbness, or tingling along the outer leg and top of the foot, often accompanied by weakness in lifting the foot.
When to Seek Professional Medical Care
While many cases of burning knee pain respond well to rest and conservative management, certain warning signs indicate a need for prompt medical evaluation. Even without acute symptoms, any persistent burning pain that interferes with sleep or daily activities should be discussed with a healthcare provider.
- Sudden, severe pain that makes it impossible to bear weight on the leg requires immediate attention to rule out a significant injury, such as a fracture or severe tear.
- A rapid onset of pronounced swelling, especially if the knee feels hot to the touch or is accompanied by redness, could signal an infection within the joint.
- A fever or chills occurring alongside the knee pain may indicate a systemic issue.
- If the burning sensation is accompanied by progressive numbness, tingling, or weakness that spreads down the leg or causes difficulty walking, it suggests a serious nerve issue.
- Any persistent burning pain that does not improve after a few days of rest, or one that interferes with sleep or daily activities, should be discussed with a healthcare provider.