[Pathology, diagnosis and therapy of patellar dislocation]

Patella dislocation in sports trauma is a common injury and is influenced by minor alterations or derangements of dynamic or static factors. The sulcus angle should not exceed 138 degrees and the Q angle should not be more than 15 degrees. Patella alta has some influence on the dislocation tendency, and so has weakness and atrophy of the musculus vastus medialis obliquus, causing muscular imbalance. Diagnosis is made via x-ray in tangential as well as a.p. and lateral view. Clinical examination of the patella reveals in lateral dislocation or redislocation can be provoked after positioning. Tenderness is present along the medial retinaculum associated with haemarthrosis in most of the cases. Conservative treatment includes evaluation of haemarthrosis and physiotherapy especially with regard to strengthening the vastus medialis obliquus. Surgery includes lateral release and medial capsular plication or transposition of the patellar tendon for correction of the Q-angle.