Knee pain without injury can be caused by various factors, including:

• Bursitis: This is a condition where tiny sacs of fluid cushioning the bones in the knee joint become infected or irritated, leading to inflammation and pain. Symptoms may include redness around the joint, tenderness at the knee, and in some cases, fever.

• Tendinitis: This occurs when tendons, which are the tissues that join muscles to the bones, become inflamed. It is a common cause of knee pain without injury, with a dull ache in the joint. Resting can alleviate the discomfort resulting from tendinitis, but medical intervention is necessary for severe cases.

• Bakers cyst: This refers to a fluid-filled swelling that occurs at the back of the knee. It can cause restriction in movements due to the swollen area, which is a possible sign of an undiagnosed knee injury. Also known as a popliteal cyst, it generally goes away on its own. In some cases, fluid drainage from the cyst is necessary for treatment.

• Osteoarthritis: This is the inflammation and swelling of the knee joint itself, which can be caused by the deterioration of the knee. It can be influenced by past injury, poor posture, obesity, and being overweight.

• Rheumatoid arthritis: This is an autoimmune disease that is similar to osteoarthritis but is often not localized to a single joint. It is indicated by stiffness, swelling, and pain.

Other possible causes of knee pain without injury include gout, pseudogout, and cancer. It is important to seek medical attention if you experience knee pain without an obvious cause, as delaying care can prolong symptoms and make them worse.