[Computerized tomography in instability of the femoropatellar joint]

Compared with normal X-ray examination, a CT scan can give more information about patellar alignment, especially close to full extension of the knee-joint. We compared the normal knee-joints of 10 volunteers with the knee-joints of 15 patients (19 recurrent luxations, 5 habitual subluxations). We were able to distinguish between instabilities with and without changes seen on the X-ray pictures, making it possible to develop a systematic concept of treatment. In the case of recurrent dislocation with radiologically visible instability, surgical repair is the treatment of choice, while for habitual subluxation without radiologically visible instability the primary treatment of choice is conservative therapy with physiotherapy and muscle training. This is successful in most cases. If physiotherapy fails surgical repair is the next step in treatment. This dynamic type of investigation (the patella is stabilized by tension of the quadriceps femoris muscle) makes an objective judgement of the result of therapy possible.