Transient Synovitis: This is the most common cause of hip pain in children, characterized by inflammation of the synovial tissue surrounding the hip joint. It often presents with sudden onset of hip pain and limping, without fever, which matches the symptoms described.

Legg-Calve-Perthes Disease: A condition where the blood supply to the head of the femur is disrupted, leading to necrosis of the bone. It typically affects children between 4 to 8 years old and presents with hip pain and limping.
Slipped Capital Femoral Epiphysis (SCFE): A condition where the growth plate in the hip joint becomes weakened, allowing the ball at the upper end of the femur to slip out of place. It is more common in early adolescence but can occur in younger children, especially those who are overweight.
Septic Arthritis (without fever): Although less likely without fever, septic arthritis is an infection within a joint and can present with pain and limping. The absence of fever does not rule out this diagnosis entirely.

Malignancy (e.g., Osteosarcoma, Ewing's Sarcoma): Although rare, bone cancers can present with hip pain and limping. Early diagnosis is crucial for effective treatment.
Juvenile Idiopathic Arthritis (JIA): An autoimmune disease that can cause joint pain and inflammation. It might not always present with systemic symptoms like fever.
Osteomyelitis: An infection of the bone that can cause pain, and while it often presents with fever, the absence of fever does not exclude this diagnosis.

Gaucher's Disease: A genetic disorder that can lead to bone pain and other systemic symptoms due to the accumulation of harmful quantities of a certain fatty substance (lipid) throughout the body.
Multiple Epiphyseal Dysplasia: A rare genetic disorder that affects the development of bone and cartilage, leading to skeletal malformations and potentially hip pain.
Sickle Cell Disease with Avascular Necrosis: In children with sickle cell disease, avascular necrosis of the femoral head can occur, leading to hip pain and limping.