Transient Synovitis: This is the most common cause of hip pain in children, often presenting with acute onset of pain and limited mobility. It is usually self-limiting and resolves within a few days.

Legg-Calve-Perthes Disease: A condition characterized by avascular necrosis of the femoral head, more common in children aged 4-8 years. It presents with hip pain, limp, and limited range of motion.
Slipped Capital Femoral Epiphysis (SCFE): A condition where the femoral head slips off the femoral neck, more common in obese children during periods of rapid growth. It presents with hip, groin, or knee pain and a limp.
Musculoskeletal Strain or Overuse Injury: Common in active children, these injuries can cause pain in the hip or groin area due to strain on the muscles or tendons.

Septic Arthritis: A bacterial infection within the joint, which is a medical emergency requiring prompt antibiotic treatment and possible surgical intervention. Symptoms include severe pain, fever, and limited mobility.
Osteomyelitis: A bone infection that can cause severe pain, fever, and swelling. It requires prompt antibiotic treatment to prevent long-term damage.
Tumor (e.g., Osteosarcoma, Ewing's Sarcoma): Although rare, bone tumors can cause persistent pain and should be considered in the differential diagnosis to ensure early detection and treatment.

Juvenile Idiopathic Arthritis (JIA): A chronic autoimmune disease that can cause joint pain and swelling. It is less common but should be considered if other diagnoses are ruled out.
Hip Fracture or Stress Fracture: Although less common in children, fractures can occur due to trauma or repetitive stress and should be considered, especially if there is a history of trauma or significant pain.
Inguinal Hernia: Can cause groin pain, especially if the hernia becomes incarcerated or strangulated, which is a surgical emergency.