Medial meniscus tear: This is a common cause of medial knee pain, especially in individuals who participate in sports or activities that involve twisting or bending of the knee. The meniscus is a cartilage structure that can be damaged, leading to pain and stiffness in the knee.

Medial collateral ligament (MCL) sprain: The MCL is a ligament that connects the femur to the tibia and provides stability to the knee. A sprain can occur due to a sudden twisting or bending motion, leading to medial knee pain.
Pes anserine bursitis: This condition occurs when the bursa that separates the MCL from the tibia becomes inflamed, causing pain and swelling in the medial knee.
Osteoarthritis: This is a degenerative joint disease that can cause pain and stiffness in the knee, especially in older adults. Medial knee pain is common in osteoarthritis due to the uneven wear and tear of the joint cartilage.

Deep vein thrombosis (DVT): Although less common, DVT can cause medial knee pain and swelling. It is essential to consider this diagnosis, especially in individuals with risk factors such as recent surgery, immobilization, or cancer.
Septic arthritis: This is a serious infection of the joint that requires prompt medical attention. Medial knee pain, swelling, and redness can be symptoms of septic arthritis.
Osteonecrosis: This condition occurs when the bone tissue dies due to a lack of blood supply, leading to pain and collapse of the bone. The medial knee can be affected, especially in individuals with risk factors such as steroid use or excessive alcohol consumption.

Medial knee tumor: Although rare, tumors such as osteosarcoma or chondrosarcoma can cause medial knee pain and swelling.
Nerve entrapment: The saphenous nerve can become entrapped, causing medial knee pain and numbness.
Stress fracture: A stress fracture of the tibia or femur can cause medial knee pain, especially in individuals who participate in repetitive activities such as running or jumping.