Luxating patella

Dislocation of the patella is a knee injury in which the knee cap (patella ) out of its guide jumps (dislocation ). In most cases, the kneecap moves spontaneously to its original position ( reduction ). They rarely remains in its contortion position outside (lateral ) of the knee joint.

The dislocation of the patella with an incidence of 5.8 / 100,000 in the general population, one of the most common knee injuries. It occurs also in animals, for example in domestic dog and domestic cat, on.

Causes

Most common cause of patellar luxation is the congenital form of the kneecap and the plain bearing ( dysplasia of the femoral trochlea ) and secondarily a deformity of the knee ( genu valgum, " knock-kneed "), a high- kneecap ( patella alta ) and lateral approach patellar tendon on the tibia. Thus, the kneecap slides tend not to be centrally located between the femoral condyles, but too far outside (lateral ). With increasing flexion may cause a dislocation. Favoring effect rotational movements of the knee joint, such as in sport, whereby the starting point of the patellar tendon is displaced outwardly so that the pulling direction of the string are changed.

Effect

The kneecap is running at the dislocation is not in their regular patellar sleeve bearing on the femoral condyle between the femoral condyles, but always laterally on the lateral condyle along. With increasing diffraction occurs for the clamping of the patella when the tendon tension increases. In this position, a reduction dislocation of the kneecap is only possible under force, with the formation of bone-cartilage damage to both the patella as well as on the side Kondylenwange. This cartilage damage is the most harmful effect of patellar dislocation. In patellar luxation, the medial ligaments of the kneecap ( patellar retinaculum ) is torn in general, where there is a bruise in the knee joint ( hemarthrosis ). Is torn or stretched retinaculum is an increased risk of repeated dislocation ( recurrence ) or even the habitual dislocation ( habitual dislocation).

Treatment

In any case - if this did not happen by itself - the patella can be put right. Here, under the guidance of the physician or an experienced sports coach, the knee should be slowly and carefully stretched again, the kneecap is out with your hand so that it does not jump abruptly. If the patella is gently guided to the starting position, it can be repositioned again without accompanying injury of the articular surfaces. It should not come to a violent snap, which can cause cartilage damage. The person noted after reduction, a significant reduction in pain. After reduction, the knee should be x-rayed and an MRI be done to check the correct position of the patella and to exclude associated injuries.

Conservative treatment

• Where appropriate, puncture of the knee joint under sterile conditions ( performed only exception as today )
• Bandage, brace or plaster sleeve ( cylinder cast )
• Physiotherapy ( mobilization, strengthening of the vastus medialis musculi quadricipitis )

Surgical treatment

With appropriate anatomical constitution ( Patelladysplasie ), the indication for surgical treatment can be provided after the first kneecap dislocation, as is to be expected in the majority of cases with recurrence. In the so-called recurrent patellar dislocation, there are various operational measures that cause the patella no longer dislocate and thereby can damage the cartilage.

The goal of surgery is to stabilize the patella centrally located between the femoral condyles in their friction bearings. For this purpose, the torn medial retinaculum is sutured to its Rißstelle. Mostly there is the crack spot right on the kneecap edge. Rarely can also be torn off at the epicondyle of the medial femoral condyle, the retinaculum. As a first measure of the surgery, a knee arthroscopy is performed to show the Retinakulumläsion in their localization to prove the integrity of the articular surfaces of the patella and the femoral condyles or confirm a possible cartilage damage in extent and localization. Next, all other joint structures ( menisci, cruciate ligaments ) must be controlled. The reconstruction of the retinaculum by seam open surgery performed because an accurate anatomical adaptation under stress is not possible arthroscopically.

A number of procedures can be carried out additionally or alternatively. This primarily includes a so-called " lateral release ", ie a limited arthroscopic or open transection of the lateral retinaculum of the patella. According to recent studies of this part of the operation leads but rather to an even greater instability of the patella. Moreover, the circulation is degraded because the patella over the lateral retinaculum receives its essential influx. during special anatomical conditions such as at a lateralization of the tendon of the kneecap shifting the approach point can ( tibial tuberosity ) together with the tendon carried medially. to this end, a variety described by surgical procedures:

• OP Roux or Elmslie ( tibial tuberosity is medially displaced distally )

In pre-damaged Retinakulumgewebe and multiple dislocations medial reconstruction must be supplemented by a band gain.

• MPFL (medial Patello - femoral ligament ) reconstruction: this will involve a tendon from the knee region used which is also used for cruciate ligament reconstruction Use: It is the tendon of the semitendinosus or gracilis. This is taken out and in the course of the medial retinaculum from the medial epicondyle to Patellakante where it is (eg, interference screws ) each fixed with implants or sewn by a V -shaped channel with itself. This ligament reconstruction produces a high security against Luxationsrezidiv.

Very rare dysplastic plain bearings is addressed surgically today. The effort here is very high and the results are usually unsatisfactory.

• Trochleaplastik, in this case the joint surface of the plain bearing is recessed to create an isosceles concave bearings and the patella a good leader.

Postoperatively, should an early physiotherapy Mobilistaion of the knee done in order to avoid early adhesions. However, a discharge of the operated leg is not necessary. After about 6 weeks to be expected with a resumption of the free function.