How to Know if your Knee is Out of Place?
In order to assess the mechanical alignment of the lower extremity, a special x-ray is obtained whereby the hip, knee and ankle joint are all imaged together with the patient standing. A line can then be drawn from the center of the hip to the center of the ankle to determine whether the patient’s knee is in neutral, varus (bow legged), or valgus (knock kneed) alignment. If the weightbearing line travels through the outer portion of the knee, the patient is in valgus alignment and more of their weight is being transmitted through the outer portion of the knee. The opposite is true in the case of a varus aligned knee, where more weight is being transmitted through the inner portion of the joint. After years of being malaligned and also being active, a patient will start to preferentially wear out the cartilage on the portion of the knee that is overloaded. Patients with valgus malalignment overload and wear the cartilage on the outside of the knee joint. Those with varus malalignment overload and wear out the cartilage on the inside of the knee.
Knee cap (patella) malalignment is also common. Instead of tracking centered in the femoral groove (trochlea), the patella may track laterally or to the outside of the groove. This is often associated with someone being in valgus. Patients with a knee cap that tracks to the outside of the knee wear the cartilage on the underside of the knee cap over time at a faster rate. Furthermore, knee caps that track to the outside are more likely to dislocate out of the groove.
Wearing out the articular cartilage of the knee joint in the setting of malalignment can be compared to wearing out the tread on your tires of your car when the wheel is out of alignment. Fortunately, these knee malalignment issues can be corrected with an osteotomy procedure. Pain relief is good but there may still be some pain as the arthritic areas of the knee are still present, but they are unweighted.