A 34-year-old woman has a direct blow to the patella by the dashboard of the vehicle during an automobile crash. The woman is admitted to the emergency depament and radiographic examination reveals patellofemoral syndrome. This type of syndrome is characterized by lateral dislocation of the patella. Which of the following muscles requires strengthening by physical rehabilitation to prevent future dislocation of the patella?

During extension of knee joint their is natural tendency of patella to dislocate laterally. The vastus medialis inses upon the medial aspect of the patella and draws it medially, especially in the last quaer of extension--during which it is especially palpable in contraction. This muscle is referred to as the vastus medialis obliqus (VMO). Increasing the strength of this muscle can lessen the lateral dislocation of the patella.