A wrong step, a twist or an unfortunate collision - it's already happened. The kneecap has popped out. In medical terms, this is known as a patellar luxation. The pain is very severe. But how does a patellar dislocation, the popping out of the kneecap, occur? Here you will find further information and selected patellar luxation specialists and centers.
The kneecap (patella) is a disc-shaped or cup-shaped bone and is located in front of the knee joint. It is embedded in the tendon of the strong muscle of the front of the thigh (quadriceps femoris muscle). The quadriceps femoris muscle is one of the strongest muscles in the human body and causes the knee joint to extend. During each extension movement, the patella glides over the knee joint and has special joint surfaces for this purpose. These form a so-called sliding bearing for the kneecap.
The kneecap in a healthy knee © Axel Kock | AdobeStock
Patellar dislocation is one of the most common injuries to the knee joint . As mentioned above, the kneecap (patella) normally sits centrally in front of the knee joint in its sliding bearing. If there is an unfortunate twisting of the knee joint or a collision, the kneecap can slip out of its bearing.
If the kneecap pops out completely, this is known as a patellar luxation. In this case, the patient is no longer able to walk and suffers severe pain. Since a severe trauma is usually necessary for a patella dislocation, a bone fracture (medically known as a patella fracture) often occurs in addition to the dislocation. In addition, a bloody joint effusion very frequently occurs, which can lead to pronounced swelling of the entire knee joint.
A patellar subluxation is sometimes observed in the case of a harmless accident with only a minor impact. In this case, the patella jumps out of its gliding bearing, but then returns to its original position by itself and solely through the movement of the muscles and the tendon pull. The prerequisite for this, however, is that the embedding of the patella in the musculature is stable and hardly damaged.
Patellar subluxation rarely results in additional injuries to the capsular and ligamentous apparatus, as the accident mechanism is less dramatic. However, patellar dislocation is often accompanied by injuries due to the strong force applied. In the worst case, severe cartilage damage can occur, especially behind the kneecap. This is the case, for example, if the kneecap is improperly put back into place or if it jumps out of its bearing with great force.
Immediately after the injury, there is severe bruising in the knee joint caused by the damage to the
and ligaments.
This is accompanied by severe pain, which can make it almost impossible to bend the leg or even walk.
It is therefore essential to seek professional treatment and physiotherapy as soon as possible in the event of a patellar dislocation.
There are several factors that can contribute to a patellar dislocation. External force, such as a collision, is the most common cause of the injury.
However, anatomical features can also increase the risk. If the leg axes are misaligned, known as knock-knees, the kneecap is pressed very close to the outer edge of the sliding bearing. This means that less force or less twisting may be required to cause this injury.
Flattened bearings also pose a risk. Patients who suffer from patella dysplasia are also at risk. This is a congenital malformation of the kneecap.
Muscles also play a role. If certain muscles are not strong enough, the kneecap can be pulled outwards and displaced as a result.
As already described in detail, the capsule-ligament apparatus of the knee joint can be considerably damaged in the case of patellar dislocations. This increases the risk of suffering a patellar dislocation again. However, and especially in the case of recurrent dislocations of the kneecap, which means that it keeps popping out, cartilage and ligament injuries can occur.
Such recurrent patellar dislocations can eventually occur after only minor force has been applied due to the damaged ligament and capsule structures of the joint. Sometimes they even occur spontaneously when walking or simply bending the knee joint.
Patellar dislocation causes very severe pain. The pain also depends on how many other structures are affected by this injury. If
are damaged, the pain is much greater than if all structures remain intact. But even without this "collateral damage" (in medicine, this refers to injury to accompanying structures), it is a very painful condition.
A patellar dislocation is accompanied by severe pain in the knee © Aleksej | AdobeStock
If a patella dislocation occurs, the affected person is often no longer able to straighten their leg. The leg is "blocked" by the displaced kneecap.
Unfortunately - especially for sensitive patients - the patella luxation can also be seen. The kneecap pops out so that the knee simply no longer looks the way it should. Not a pretty sight, but an unmistakable sign that the patella has slipped out of its bearing.
Depending on which additional structures are damaged, this can also lead to a feeling of instability in the knee joint.
First of all, the kneecap must be professionally repositioned by an orthopaedic surgeon. This procedure is very painful. Some patients require anesthesia or strong painkillers. The leg must then be immobilized with a so-called Mecron splint. This keeps the leg straight and provides relief.
Now comes the crucial question: should the patellar dislocation be followed by surgery or conservative treatment?
If it is "only" a dislocation of the patella and no other structures have been damaged, conservative treatment can be initiated. The first step is to get the swelling out of the knee. This is followed by mobilization and targeted physiotherapeutic treatment to build up the muscles. The muscles on the front of the thigh are important here, as they hold the kneecap in place and help to center it.
If there are recurring dislocations or if other structures are damaged, an operation is usually performed as part of knee surgery. The damaged structures are first repaired before a so-called "lateral release" can be performed. This shifts the kneecap back to the inside.
Physiotherapy is essential both for conservative treatment by means of reduction and temporary immobilization, but also after surgery. It has an influence on when athletes can resume their sport, for example. This is particularly important in the case of anatomical conditions such as knock-knees, which can promote patellar dislocation. Although there is never 100% certainty, the risk of a new dislocation can be minimized through targeted movement and muscle training.
Physiotherapy is necessary after a patellar dislocation © contrastwerkstatt | AdobeStock
However, if the kneecap is dislocated, a visit to a specialist is essential. He or she will initiate the next steps and also discuss with the patient whether or not surgery is necessary. A patellar dislocation must always be followed by comprehensive therapy, as follow-up treatment is an important step towards complete healing.
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