Differential Diagnosis for Medial Knee Pain after Running

• Single most likely diagnosis
  • Medial meniscus tear: This is a common injury in runners, especially if they have a history of sudden stops, twists, or pivots. The meniscus is a cartilage structure in the knee joint that can become damaged, leading to pain, especially on the medial (inner) aspect of the knee.
• Other Likely diagnoses
  • Medial collateral ligament (MCL) sprain: The MCL is a ligament that connects the femur (thigh bone) to the tibia (shin bone) on the medial side of the knee. It can become stretched or torn, leading to pain and instability, particularly after activities that involve running or sudden changes in direction.
  • Pes anserine bursitis: This condition involves inflammation of the bursa located on the medial aspect of the knee, where the tendons of the sartorius, gracilis, and semitendinosus muscles attach. Running can irritate this bursa, leading to pain and swelling.
  • Medial tibial stress syndrome (shin splints): Although more commonly associated with anterior (front) leg pain, medial tibial stress syndrome can also cause pain on the medial side of the knee due to overuse or repetitive stress on the tibia.
• Do Not Miss diagnoses
  • Osteonecrosis of the knee: A condition where the bone tissue dies due to lack of blood supply. It can cause severe pain, especially after activity, and is crucial to diagnose early to prevent further damage.
  • Infection (septic arthritis): Although rare, an infection within the knee joint can cause severe pain, swelling, and warmth. It is a medical emergency requiring prompt diagnosis and treatment.
  • Tumor: Bone or soft tissue tumors around the knee can cause pain that worsens with activity. While rare, missing a diagnosis of a tumor could have significant consequences.
• Rare diagnoses
  • Pellegrini-Stieda syndrome: A condition characterized by ossification of the MCL, which can cause chronic medial knee pain.
  • Medial knee instability due to a posterior medial meniscofemoral ligament injury: A less common ligament injury that can lead to medial knee pain and instability.
  • Referral pain from the hip or lower back: Sometimes, pain from the hip or lower back can refer to the medial knee area, especially if there are issues with the nerves or spinal discs.