Patellar dislocation

People often describe pain as severe and being "inside the knee cap". The leg tends to flex even when relaxed. In some cases, the injured ligaments involved in patellar dislocation do not allow the leg to flex. ==Risk factors==

A predisposing factor is tightness in the tensor fasciae latae muscle and iliotibial tract in combination with a quadriceps imbalance between the vastus lateralis and vastus medialis muscles can play a large role, found, mainly, in women involved in sports. Moreover, women with patellofemoral pain may show increased Q-angle compared with women without patellofemoral pain. Another cause of patellar symptoms is lateral patellar compression syndrome, which can be caused from lack of balance or inflammation in the joints. The pathophysiology of the kneecap is complex, and deals with the osseous soft tissue or abnormalities within the patellofemoral groove. The patellar symptoms cause knee extensor dysplasia, and sensitive small variations affect the muscular mechanism that controls the joint movements. 24% of people whose patellas have dislocated have relatives who have experienced patellar dislocations. It is more common in females than males and in young in-training military personnel who have a high incidence of patellar dislocation in relation to young athletes and the general population. An angle greater than 25 degrees between the patellar tendon and quadriceps muscle can predispose a person to patellar dislocation. In patella alta, the patella sits higher on the knee than normal. ==Mechanism of injury==

Patellar dislocations occur by: • A direct impact that knocks the patella out of joint • A twisting motion of the knee, or ankle • A sudden lateral cut The medial patellofemoral ligament attaches horizontally in the inner knee to the adductor magnus tendon and is the structure most often damaged during a patellar dislocation. Finally, the lateral collateral ligament and the medial collateral ligament stabilize the patella on either side. Any of these structures can sustain damage during a patellar dislocation. ==Diagnosis==

To assess the knee, a clinician can perform the Patellar Aprehension Test by moving the patella back and forth while the people flexes the knee at approximately 30 degrees. The people can do the patella tracking assessment by making a single leg squat and standing, or by lying on his or her back with knee extended from flexed position. A patella that slips laterally on early flexion is called the , and indicates imbalance between the VMO and lateral structures. On X-ray, with skyline projections, dislocations are readily diagnosed. In borderline cases of subluxation, the following measurements can be helpful: • The lateral patellofemoral angle, formed by: :*A line connecting the most anterior points of the medial and lateral facets of the trochlea. :*A tangent to the lateral facet of the patella. :With the knee in 20° flexed, this angle should normally open laterally. • The patellofemoral index is the ratio between the thickness of the medial joint space and the lateral joint space (L). With the knee 20° flexed, it should measure 1.6 or less. File:Lateral patellofemoral angle.jpg File:Lateral and medial joint space of patella.jpg ==Prevention==

The patella is a floating sesamoid bone held in place by the quadriceps muscle tendon and patellar tendon ligament. Exercises should strengthen quadriceps muscles such as rectus femoris, vastus intermedius, and vastus lateralis. However, tight and strong lateral quadriceps can be an underlying cause of patellar dislocation. If this is the case, it is advisable to strengthen the medial quadriceps, vastus medialis (VMO), and stretch the lateral muscles. Exercises to strengthen quadriceps muscles include, but are not limited to, squats and lunges. Adding extra external support around the knee by using devices such as knee [orthotics] or athletic tape can help to prevent patellar dislocation and other knee-related injuries. External supports, such as knee braces and athletic tape, work by providing movement in only the desired planes and help hinder movements that can cause abnormal movement and injuries. Women who wear high heels tend to develop short calf muscles and tendons. Exercises to stretch and strengthen calf muscles are recommended on a daily basis. ==Treatment==

Two types of treatment options are typically available: • Surgery • Conservative treatment (rehabilitation and physical therapy) Surgery may impede normal growth of structures in the knee, so doctors generally do not recommend knee operations for young people who are still growing. There are also risks of complications, such as an adverse reaction to anesthesia or an infection. • Concurrent osteochondral injury • Continued gross instability • Palpable disruption of the medial patellofemoral ligament and the vastus medialis obliquus • High-level athletic demands coupled with mechanical risk factors and an initial injury mechanism not related to contact Supplements like glucosamine and NSAIDs can be used to minimize bothersome symptoms. == Epidemiology ==

Rate in the United States are estimated 2.3 per 100,000 per year. Rates for ages 10–17 were found to be about 29 per 100,000 persons per year, while the adult population average for this type of injury ranged between 5.8 and 7.0 per 100,000 persons per year. The highest rates of patellar dislocation were found in the youngest age groups, while the rates declined with increasing ages. Females are more susceptible to patellar dislocation. Race is a significant factor for this injury, where Hispanics, African-Americans and Caucasians had slightly higher rates of patellar dislocation due to the types of athletic activity involved in: basketball (18.2%), soccer (6.9%), and football (6.9%), according to Brian Waterman. The treatment of the skeletally immature is controversial due to the fact that they are so young and are still growing. Surgery is recommended by some experts in order to repair the medial structures early, while others recommend treating it non operatively with physical therapy. If re-dislocation occurs then reconstruction of the medial patellofemoral ligament (MPFL) is the recommended surgical option. In animals, patellar luxation is a common condition in dogs, particularly small and miniature breeds. == References ==