What is the treatment for patella dislocation

Kneecap Dislocation - Patellar Dislocation

In the case of patellar dislocation, the kneecap jumps out of its V-shaped bony guide groove on the thigh bone to the outside. In addition, there are often injuries to the ligaments on the inside of the knee joint as well as to the bones and cartilage on the kneecap and thighbones.


Occurrence

Typically, adolescent slim female athletes are affected by this injury. The first event of a patellar luxation usually occurs before the age of 20.

Usually, a patellar dislocation results from twisting the slightly bent knee joint while simultaneously tensing the thigh extensor muscles (e.g. dancing, gymnastics); very rarely, a direct side impact is the cause of the injury.

Risk factors for a patellar dislocation are a general weakness of the connective tissue (hyperlaxity), female gender, axial misalignments (knock knees), congenital malformations of the kneecap (patella) or patellar sliding bearings (trochlea femoris), a congenital or accident-related high position of the kneecap and a weakness or imbalance of the kneecap Thigh extensor muscles.


Classification

The first dislocation of the kneecap as a result of a real accident (fall, blow, impact) is called the traumatic first dislocation of the patella. Further patellar dislocations following a traumatic initial dislocation are referred to as chronic recurrent post-traumatic patellar dislocations. A patellar dislocation without a real accident event is a habitual patellar dislocation. Congenital or congenital patellar luxation is a rarity. It usually occurs on both sides and in connection with a systemic disease of the musculoskeletal system with further deformities.


diagnosis

Acute patellar dislocation is a visual diagnosis. The kneecap is on the outside of the knee joint, the plain bearing is empty. However, after a patellar dislocation, spontaneous self-reduction without manipulation of the kneecap often occurs. In these cases, an exact medical history (anamnesis) is important. After repositioning, one can often feel and also see an effusion of the knee joint. Depending on the severity of the injury and the pre-existing ligament stability, the area on the inside of the kneecap and on the outer edge of the sliding channel on the thigh is painful when pressed. If one carefully tries to induce a new dislocation by exerting pressure on the kneecap, the patients defend themselves against it after the patellar dislocation has already taken place, as they know this feeling of the impending dislocation exactly (so-called apprehension test).

In order to diagnose concomitant injuries, a puncture of the knee joint as well as an X-ray of the knee joint in 3 planes and, if necessary, an MRI should be performed.

Concomitant injuries often include a bloody knee joint effusion, tearing of the holding apparatus of the kneecap on the inside (medial patellofemoral ligament, medial retinaculum patellae) of the knee joint and shearing off of bone and cartilage fragments (flake fractures) on the inner edge of the gliding facet of the kneecap on the thigh.

 

Tangential x-ray of the patella. Bony fragments on the inside of the patella and thigh.

Magnetic resonance imaging (MRI) of the knee joint after patellar dislocation. Cartilage defect on the patella (white arrow), free cartilage-bone fragment on the outside of the sliding channel (transparent arrow) and tearing of the inner holding apparatus (white star).


therapy

The first immediate measure is the immediate reduction of the patellar dislocation with extension of the knee joint and simultaneous flexion of the hip joint to relax the thigh extensor muscles. If the patient is very painful and has cramping, it may be necessary to administer pain relievers and sedatives intravenously for reduction. If the knee joint effusion is palpable, the knee joint should be punctured. On the one hand, this has a pain-relieving effect through pressure relief; on the other hand, blood can also have a damaging effect on the cartilage surface and should therefore be removed from the joint. Furthermore, fat eyes floating on the blood are an important indicator of the presence of an accompanying bone injury.

After the first patellar dislocation, the risk of a further such injury is around 30%. Any dislocation of the patella means a serious injury to the knee joint with the risk of cartilage damage and the formation of scarring as a result of an inflammatory reaction. With each subsequent dislocation, the risk of further dislocations increases. Therefore, the first dislocation of the patella is usually treated without surgery. This is done by immobilizing the knee joint in a stretched position in a splint (orthosis) for about 3-4 weeks. With the splint on, full weight bearing on the injured leg is permitted. If it occurs again, however, an operation to stabilize the kneecap should be carried out, especially for athletes. A distinction is made between interventions on the connective tissue and interventions on the bones. Which operation is necessary or useful is decided after a detailed examination of the knee joint including a measurement of the leg axes.

Often the first surgical intervention is gathered over an approximately 4 cm long skin incision, the inner holding apparatus of the kneecap and sutured in several layers so that the kneecap is pulled more inward (medial gathering). A simultaneous severing of the outer holding apparatus of the kneecap (lateral release) should only take place if the kneecap cannot be moved inwards at all. Otherwise you risk an additional destabilization of an already unstable joint. Bony interventions such as relocating the insertion of the kneecap tendon (patellar tendon) on the tibial head inward (Elmslie-Trillat operation) should only be carried out after growth has been completed. If the operation is unsuccessful or if relevant axis misalignments are present, several procedures can be carried out in combination.


Aftercare

The follow-up treatment depends on the selected surgical procedure. In general, the inner thigh extensor should be strengthened through physiotherapy and then increasingly through constant independent training in order to favorably influence the direction of pull on the kneecap.


forecast

In the medium and long term, even with optimal treatment of a patellar dislocation, damage to the cartilage surfaces of the kneecap and its sliding channel on the thigh must be expected, which can ultimately result in premature wear of the joint between the kneecap and thigh (retropatellar arthrosis). The primary aim of the treatment is therefore to avoid these signs of wear and tear or to delay them as long as possible and to maintain a permanent, pain-free function of the knee joint.