The problem of patellar instability is fairly common, especially among the young, athletic population. Instability usually means the patella (kneecap) has dislocated more than once. This condition poses a treatment challenge because of the unique and complex anatomy and biomechanics of the patellofemoral joint (where the kneecap articulates or moves against the leg bones).
The Q-angle figures in because it is the angle of pull of the quadriceps muscle on the patella. An increased Q-angle results in pulling the patella laterally (toward the outside of the joint away from the other knee). With enough pull and not enough restraint, the patella can be pulled so far over that it pops out of the groove and dislocates.
But there are other important anatomical features contributing to patellar stability/instability. For example, the surrounding fascia (connective tissue), shape of the patella, depth of the trochlear groove, and other ligaments (e.g., meniscofemoral ligament, posterior oblique ligament) can affect how the patella moves up and down over the leg.
Most of these soft tissue structures provide restraint, a force known to hold the patella in place where it belongs. Change in any one of these factors can result in rotation or translation of the patella away from the trochlear groove. When that happens the patella can sublux (partial dislocation) or fully dislocate.
It might be a good idea to see an orthopedic specialist for an evaluation of your knee before jumping to any conclusions about surgery. A sports medicine physician or orthopedic surgeon examines the patient, performing necessary tests to document patellar instability. Knee range-of-motion and quality of patellar motion are observed and measured. The various ligaments can be palpated and/or tested for integrity or deficiency.
The strength and quality of muscular contraction are assessed for the quadriceps muscle. The Q-angle, which is the angle of pull of the quadriceps muscle on the patella is measured. An increased Q-angle results in pulling the patella laterally (toward the outside of the joint away from the other knee). With enough pull and not enough restraint, the patella can be pulled so far over that it pops out of the groove and dislocates.
Sometimes imaging studies can be helpful. X-rays have the least value in this area. Unless the patella is fractured or there are bone spurs, X-rays don’t really show any problems that would confirm a diagnosis of chronic patellar instability or offer information as to why the problem is occurring. CT scans can show an abnormal tilt of the patella and give some information about the bony prominence (the tibial tubercle) that inserts into the trochlear groove. MRIs can show ligament damage and even bone bruises from a recent patellar dislocation.
The first-line of treatment is nonoperative with activity modification, taping, bracing, and exercises. Surgery is only indicated when conservative (nonoperative) care fails to improve symptoms and/or the patella continues to dislocate.