Limb length inequality occurs when one limb is shorter than the other. Limb length inequality in children is often due to fractures, trauma, infections, or genetic conditions. The femur and tibia, like other long bones in the body, do not grow evenly from the center outward. Instead, their growth occurs at the growth plates, which are specialized areas of cartilage situated between the metaphysis (the main shaft of the bone) and the epiphysis (the end of the bone). As a child grows, the cartilage in the growth plates gradually hardens into bone, contributing to the overall lengthening of the femur and tibia until growth stops in adulthood.
Limb length discrepancies can be caused by trauma, such as broken bones or injuries to the growth plate, which affect how the bone grows. Bone infections in infants, and bone diseases like neurofibromatosis and multiple hereditary exostoses can also lead to discrepancies. In some cases, the cause is unknown, which is referred to as idiopathic, or the discrepancy results from developmental issues like hemihypertrophy or hemiatrophy, where one side of the body grows differently than the other.
It is estimated that more than 50% of individuals have a slight leg length discrepancy, which usually doesn’t lead to any significant issues. However, for a small percentage of people, when the leg length difference exceeds 2 cm, it can result in discomfort, mobility issues, and a noticeable impact on their quality of life. The femur (thighbone) and tibia (shinbone) are typically the bones involved in these discrepancies, and when one of these bones is shorter, it can cause complications ranging from altered gait to pain in the hips, knees, and lower back.
While differences in arm length usually don’t affect functionality, a leg length discrepancy can lead to problems particularly with walking, balance, and other physical movements. In severe cases, it may require medical intervention to correct or manage the condition and improve functionality.
One option for children still growing is epiphysiodesis. This procedure involves slowing or stopping growth at one or two growth plates in the longer leg, using a minor surgical technique. The key advantage is that it doesn’t involve cutting the bone, and the child doesn’t face prolonged weight-bearing restrictions. However, the child must still be skeletally immature (growth plates open), meaning there is still enough growth potential in the normal leg to help balance the leg lengths over time.