Why Is One Knee Swollen but Not the Other? – Story Of The Day!

It is here that we must address the more serious, non-mechanical causes of unilateral swelling. If a knee is swollen, red, and hot to the touch, it may be a sign of an infection, known as septic arthritis.¹⁰ This is a true medical emergency where bacteria have entered the joint space, often through a small cut or even through the bloodstream from an infection elsewhere in the body.¹¹ Unlike a simple sprain, an infected knee is typically accompanied by a fever and an inability to bear any weight on the leg.¹² Similarly, crystalline arthropathies like gout or pseudogout can strike a single joint with terrifying speed. In these cases, uric acid crystals (gout) or calcium pyrophosphate crystals (pseudogout) deposit within the joint, causing an inflammatory storm that looks identical to an injury but is actually a metabolic event focused on one location.¹³+3

Furthermore, we cannot ignore the vascular implications. While “swelling” usually refers to the joint itself, a Deep Vein Thrombosis (DVT)—a blood clot in the leg—can cause the area around and below the knee to expand significantly.¹⁴ This is a life-threatening situation, as the clot can travel to the lungs.¹⁵ If the swelling is associated with calf pain, a “heavy” feeling in the leg, or skin that is bluish or discolored, immediate emergency intervention is required.+1

Living with a lopsided body is a lesson in patience and self-care. When you encounter one-sided swelling, the first line of defense is often the R.I.C.E. protocol: Rest, Ice, Compression, and Elevation.¹⁶ By elevating the knee above the level of the heart, you assist the lymphatic system in draining the excess fluid that the inflammatory response has gathered.¹⁷ However, self-treatment has its limits. If the swelling is the result of a significant impact, if the joint looks visibly deformed, if you cannot bear weight, or if you feel a systemic sense of illness such as a fever, the time for home remedies has passed.+1