Miserable Malalignment Syndrome

Anatomy

At birth, there is a normal rotational alignment of the femurs (thighbone) and the tibias (shinbones) from top to bottom, which changes throughout the process of skeletal development. The bottom portions of both the femur, near the knee, and the tibia, near the ankle joint, begin by being rotated inward slightly, relative to the tops of the bones, and slowly rotate outward with increasing growth. When this process does not progress to a normal degree in the femur, the patient is said to have abnormally high “femoral anteversion.” Notably, females normally have higher anteversion than males, which puts them at greater risk of having this abnormal condition. When this occurs too much in the tibia, the patient is said to have external tibial torsion, which can leave the feet splayed outward to some degree.

When abnormal femoral anteversion and external tibial torsion occur together, patellofemoral pain and other problems, such as patellar instability, can develop because of the effect on the Q angle of the knee. The Q angle is the angle formed by a line drawn from the anterior superior iliac spine (ASIS; a point on either side of the front of the pelvis) to the middle of the top of the patella (kneecap) and a second line drawn from the middle of the bottom of the patella to the tibial tubercle (the prominence at the top of the shinbone, which serves as the [Page 873]insertion of the patellar tendon). Because the knee and patella are rotated inward with femoral anteversion and the tibial tubercle is rotated outward with external tibial torsion, this combination creates an abnormally high Q angle. As a result, the patella has an abnormally high vector of force pulling it laterally to the outside of the knee.

Causes

Femoral anteversion and external tibial torsion are generally thought to be extremes of the physiologic spectrum of rotational development during skeletal maturation. Increased knee Q angle can be caused by other factors, such as a tight lateral retinaculum (connective tissue that runs from the patella to the side of the femur, along with the joint capsule) or genu valgum (knock-knees), but femoral anteversion and external tibial torsion are among the most common causes.

Symptoms

The primary symptom of MMS is patellofemoral, or anterior, knee pain. Patellar instability, in which the kneecap partially slides (subluxes) or dislocates out of its normal groove to the outside of the knee, can also occur in a small number of patients.

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