The commonest cause of limp in a child of seven years is -
The most common cause of limp in a child between 3-10 years is transient synovitis of hip.
However, among the given options Perthe's disease is the best answer as Perthes disease is the second most common cause of limp in a child between 5-10 years.
T.B. hip
C.D.H
Perthe's disease
Slipped upper femoral epiphysis