What are some signs you are about to haw a growth spurt? my sister has never had one.

Growth Spurt: The beginning of the increase in growth velocity is about age 11 in boys and 9 in girls but varies widely from individual to individual. The peak height velocity occurs at a mean of 13.5 years in boys and 11.5 years in girls. Pubertal growth accounts for about 20% of final adult height, a total averaging 23-28 cm in females and 26-28 cm in males. The average growth spurt lasts 24-36 months.