Medial Tibial Stress Syndrome (Shin Splints): This is the most common cause of lower shin pain in adolescents, especially those involved in sports or activities that involve running or repetitive stress on the legs. The pain is typically diffuse and located on the medial aspect of the tibia.

Stress Fractures: These are small cracks in the bone that can occur due to repetitive stress, common in athletes. The pain is usually more localized than in shin splints and can be severe.
Compartment Syndrome: This condition involves increased pressure within the muscle compartments of the leg, leading to pain, swelling, and sometimes weakness. It can be acute or chronic.
Periostitis: Inflammation of the periosteum, the layer surrounding the bone, can cause shin pain. It's often related to overuse or direct trauma.

Osteosarcoma: Although rare, this is the most common primary malignant bone tumor in adolescents. Shin pain, especially if accompanied by swelling, redness, or systemic symptoms like weight loss, should prompt consideration of this diagnosis.
Ewing's Sarcoma: Another rare but critical diagnosis, Ewing's Sarcoma is a malignant bone tumor that can present with pain, swelling, and sometimes fever.
Infection (Osteomyelitis): Bacterial infection of the bone can cause severe pain, swelling, redness, and systemic symptoms like fever. It's a medical emergency requiring prompt treatment.

Hypertrophic Pulmonary Osteoarthropathy: A rare condition associated with lung diseases, characterized by clubbing of the fingers, joint pain, and periostitis, which can cause shin pain.
Fibrous Dysplasia: A condition where normal bone is replaced with fibrous tissue, leading to weakened bones and potential for pain or fractures.
Chronic Exertional Compartment Syndrome: A rare condition where increased pressure within the muscle compartments occurs during exercise, leading to pain and potentially long-term damage if not addressed.