Medial Tibial Stress Syndrome (MTSS): This is the most common cause of medial distal tibia pain in runners, often due to overuse or repetitive stress on the tibia, leading to inflammation of the periosteum.

Stress Fracture: A common injury in runners, stress fractures can occur in the distal tibia due to repetitive stress and overuse, leading to a small crack in the bone.
Posterior Tibial Tendinitis: Inflammation of the posterior tibial tendon, which runs along the medial aspect of the ankle and distal tibia, can cause pain in this region, especially with activities that involve repetitive ankle motion.
Periostitis: Inflammation of the periosteum, a layer of tissue covering the bone, can cause pain and swelling in the medial distal tibia, often due to overuse or direct trauma.

Compartment Syndrome: A serious condition that occurs when pressure within the muscle compartments increases, leading to inadequate blood supply to the muscles and nerves. It requires prompt medical attention to prevent long-term damage.
Osteomyelitis: A bone infection that can cause pain, swelling, and redness in the affected area, including the medial distal tibia. It is a serious condition that requires prompt antibiotic treatment.
Tumor: Although rare, a tumor in the distal tibia can cause pain and should not be missed, as early diagnosis and treatment are crucial for prognosis.

Shin Splints due to Flexor Digitorum Longus Tendinitis: Inflammation of the flexor digitorum longus tendon, which runs along the medial aspect of the distal tibia, can cause pain in this region, although it is less common than other causes of shin splints.
Popliteus Tendinitis: Inflammation of the popliteus tendon, which is located at the posterior aspect of the knee but can refer pain to the distal tibia, is a rare cause of medial distal tibia pain in runners.