Blount disease is a condition of bowlegged knees, also known as tibia vara in medical lingo. Surgical correction aims to create a more normal angle between the lower end of the femur (thigh bone) and the upper portion of the tibia (lower leg bone). Children with Blounts disease often need surgery to restore normal knee alignment and reduce pain. The result is decreased disability and improved function.
Two angles used to diagnosis Blount disease are measured on X-rays: the metaphyseal-diaphyseal angle (MDA) and femoral-tibial angle (FTA). A MDA angle between 11 and 15 degrees is borderline tibia vara. More than 15 degrees increases the risk that tibia vara (the bowlegged position of the knee) will continue to get worse over time. For optimal results and patient satisfaction, surgeons try to achieve a metaphyseal-diaphyseal angle between -5 and +5 degrees and a femoral-tibial angle anywhere from zero and +5 degrees.
When these angles are lined up, there is a more normal and even distribution of weight and load on the upper tibia. Without correction, too much pressure is placed on the lateral (outside edge) of the knee. Ligaments on the inside (medial) edge of the knee get stretched out to the point that the knee can become unstable. In a growing child, these uneven pressures can create a leg length difference and even more deformity.
Studies show patient satisfaction increases as pain decreases and as function improves. That’s why restoring more normal anatomical angles is so important. The decisions you make as parents today may affect your daughter’s quality of life in years to come. Your surgeon will help you make the best choice based on current evidence available at this time and the severity of your daughter’s condition.