Redness on the knees can be common, stemming from various sources. While often minor, it can also signal underlying conditions requiring attention. Understanding these reasons, from everyday factors to medical situations, helps determine appropriate action.
Everyday Causes of Red Knees
Red knees often result from daily activities or environmental exposures. Friction, from repetitive kneeling on hard surfaces, can irritate the skin and underlying bursa. Tight clothing or rough fabrics can also create friction, leading to localized redness. Minor injuries like scrapes or bumps from falls result in temporary redness, swelling, and bruising.
Dry skin can also cause redness. When skin lacks moisture, it can become irritated, flaky, and appear discolored. Environmental factors like cold, dry air or excessive sun contribute to skin irritation and redness. These occurrences resolve with time and basic care, such as moisturizing or avoiding irritants.
Dermatological Conditions and Allergies
Skin conditions can also cause knee redness, often with other symptoms. Contact dermatitis, an inflammatory skin reaction, can cause an itchy rash that appears red, sometimes with bumps or blisters. This condition occurs when the skin comes into direct contact with an irritant, like harsh soaps or detergents, or an allergen, such as certain fabrics, fragrances, or plants like poison ivy. The reaction is confined to the area of contact and can develop within minutes to hours of exposure, lasting several weeks.
Eczema, particularly atopic dermatitis, affects skin creases, including the back of the knees. This condition presents as dry, itchy patches that can appear red, purple, brown, or gray depending on skin tone. Eczema can also lead to thickened, scaly, or crusty skin, and symptoms may worsen with skin rubbing or sweat.
Psoriasis is another chronic skin condition characterized by raised, inflamed skin patches, or plaques, often covered with silvery-white scales. These plaques appear on the knees and elbows, and the affected skin can be itchy or sore. Inverse psoriasis, a specific type, can occur in skin folds like the back of the knees, presenting as smooth, sometimes shiny, discolored patches.
Inflammation and Infection
Inflammation or infection can also cause red knees. Bursitis is an inflammation of the bursae, which are small fluid-filled sacs that cushion pressure points around joints. When a bursa in the knee becomes inflamed, often due to frequent kneeling, direct trauma, or infection, it can lead to warmth, tenderness, swelling and redness in the affected area.
Various forms of arthritis can cause redness and inflammation in the knee joint. Osteoarthritis, resulting from the breakdown of cartilage, can cause bones to rub together, leading to irritation, swelling, and sometimes redness and warmth over the knee. Rheumatoid arthritis, an autoimmune disease where the immune system attacks joint linings, causes pain, stiffness, swelling, warmth, and redness in the knees, often affecting both sides of the body. Gout, a type of inflammatory arthritis caused by excess uric acid forming crystals in joints, can manifest as sudden, intense pain, swelling, and severe redness, with the affected skin feeling hot to the touch. Psoriatic arthritis, which affects some individuals with psoriasis, can also cause joint inflammation, leading to pain, stiffness, swelling, and redness in the knees.
Cellulitis is a bacterial skin infection that can cause rapidly spreading redness, swelling, warmth, and tenderness in the affected area. This infection can be accompanied by fever and can spread quickly, requiring prompt medical attention. Less common, fungal infections like ringworm can also cause red, itchy, scaly patches on or around the knees.
When to Consult a Healthcare Professional
While some red knees resolve with minor care, certain symptoms warrant professional medical evaluation. Consult a healthcare provider if the redness is persistent, severe, or spreads rapidly. Accompanying symptoms like intense or increasing pain, significant swelling, warmth, or tenderness can indicate a serious underlying issue.
Other concerning signs include fever, pus draining from the affected area, or red streaks leading away from the knee, which may suggest an infection. If the redness interferes with daily activities, causes difficulty bearing weight on the knee, or is accompanied by joint locking or a feeling of instability, seek medical attention. Timely diagnosis and treatment are important for conditions that could lead to complications or long-term joint damage.