Osteoarthritis: This is a common condition that affects the joints, causing pain and stiffness, especially in older adults. Bilateral knee pain is a hallmark symptom, making it the most likely diagnosis.

Overuse Injury: Repetitive strain or overuse can lead to bilateral knee pain, especially in individuals who engage in activities that involve running, jumping, or cycling.
Patellofemoral Pain Syndrome: This condition is characterized by pain around or behind the patella (kneecap), often caused by activities that put stress on the knee, such as climbing stairs or squatting.
Meniscal Tears: Tears in the menisci, which are cartilage structures in the knee joint, can cause bilateral knee pain, especially if the tears are degenerative or caused by repetitive strain.

Septic Arthritis: Although less common, septic arthritis is a serious condition that requires prompt medical attention. It is characterized by joint pain, swelling, and fever, and can lead to severe consequences if left untreated.
Osteonecrosis: This condition, also known as avascular necrosis, occurs when there is a loss of blood supply to the bone, leading to bone death. It can cause severe knee pain and requires prompt medical attention to prevent further damage.
Rheumatoid Arthritis: This autoimmune disorder can cause bilateral knee pain, swelling, and stiffness, and requires early diagnosis and treatment to prevent joint damage and disability.

Hemochromatosis: This genetic disorder causes the body to absorb too much iron, leading to joint pain and other symptoms. Although rare, it can cause bilateral knee pain and requires early diagnosis and treatment to prevent complications.
Gaucher's Disease: This rare genetic disorder can cause joint pain, including bilateral knee pain, due to the accumulation of fatty substances in the joints and other organs.
Sarcoidosis: This condition causes inflammation in various parts of the body, including the joints, and can lead to bilateral knee pain, although it is a rare cause of this symptom.