Growing Pains: This is the most common cause of recurrent leg pain in children, especially during periods of rapid growth. The pain is typically bilateral, occurs in the late afternoon or evening, and resolves by morning. It's often described as a dull ache or soreness in the thighs, calves, or behind the knees.

Overuse Injuries: Given the age and potential for increased physical activity, overuse injuries such as shin splints or stress fractures could be considered, especially if the pain is more localized or associated with specific activities.
Musculoskeletal Strains: Strains from sports or physical activities are common in this age group and could present with pain, especially if the activity level has recently increased.
Benign Hypermobility Syndrome: Some children, especially girls, may experience joint pain due to hypermobility, which could be mistaken for growing pains but might also involve joint laxity and occasional subluxations.

Leukemia: Although rare, leukemia can present with bone pain, especially at night, and must be considered to avoid a delayed diagnosis. Other signs might include fatigue, weight loss, and petechiae.
Osteomyelitis or Septic Arthritis: Infections of the bone or joint can cause severe pain and must be promptly diagnosed and treated to prevent long-term damage.
Stress Fractures: While considered in the likely diagnoses due to overuse, stress fractures can sometimes present atypically and are important not to miss due to the risk of progression to complete fracture if not properly managed.

Juvenile Idiopathic Arthritis (JIA): An autoimmune condition that can cause joint pain and swelling. It's less common but should be considered if the pain is persistent, especially with morning stiffness or swelling.
Bone Tumors: Both benign and malignant bone tumors can cause pain, although they are rare in this age group. Night pain or pain at rest is more suggestive of a tumor.
Sickle Cell Disease: If the child has not been previously diagnosed, sickle cell disease could present with episodes of pain due to vaso-occlusive crises, although other signs such as anemia or previous episodes of pain might be present.