Patellaluxation

In patellaluxation the kneecap has "jumped out", that is, it no longer sits properly in the knee joint. Continue reading!

Patellaluxation

At a Patellaluxation the kneecap "jumped out", that is, she is no longer in the middle in front of the knee joint. The patella is an important part of the joint and allows optimal transfer of the front thigh muscles in a movement of the lower leg. Patellar luxation often causes the kneecap to slide back to its original position by itself, but the knee should always be examined by a doctor and, if necessary, treated.

ICD codes for this disease: ICD codes are internationally valid medical diagnosis codes. They are found e.g. in doctor's letters or on incapacity certificates. M22S83

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Patellaluxation

  • What happens during the patellar luxation?

  • Symptoms and concomitant injuries of a patellar dislocation

  • How does the doctor investigate the patellar dislocation?

  • Apparative diagnosis of patellar dislocation

  • How to Treat Patellar Luxation

  • Surgical procedure for patellar dislocation

  • The prognosis of a patellar luxation

What happens during the patellar luxation?

The knee joint

The knee joint allows the flexion and extension of the lower leg. It consists of two joints, the popliteal joint and the patellar joint. The lower end of the femur forms a groove in front, in which the kneecap can slide. She drives us down like a sled and covers a distance of almost 10 centimeters between the flexion and extension of the lower leg.

The task of the patella is to strengthen the force of the thigh muscle. Without a kneecap we would have great problems to stretch our lower legs and would have to spend much more power.

The patella is held in position by the femoral muscle, a sinewy fibrous ring (retinaculum), and a strong tendon on the tibial bone (patellar tendon). If one of the ligaments or parts of the thigh muscle is too strong or too weak, a biomechanical imbalance will result and the patella may slip out of the side of its groove.

Forms of patellar luxation

However, patellar dislocation is a rare event in normal knee joint development. Most commonly it occurs in slim women in sports accidents. By a pronounced force on the patella, for example, with bent knee and tense thigh muscles, the patella can jump out of the trough.

In many cases, however, those affected have certain risk factors that favor patellar dislocation. These are anatomical malformations or systemic diseases that destabilize the connective tissue or muscles. For example, people with pronounced X-legs (genu valgum) are prone to patellar dislocations because the axial malalignment increases lateral pull on the kneecap. In systemic diseases such as Marfan syndrome or also the Ehlers-Danlos syndrome there is a general weakness of the connective tissue.

With certain malformations jumped out already from birth on the kneecap and luxates immediately again, if one tries to retreat. This is called congenital patellar luxation.

But even if there are no other risk factors, initial patellar luxation increases the likelihood of further dislocations because the patellar joint has become more unstable.

Symptoms and concomitant injuries of a patellar dislocation

Patellar dislocation is associated with severe pain. When the kneecap has jumped out, the patients usually hold the leg gently bent and are no longer able to move the lower leg due to the pain.

Occasionally, dislocation leads to small fractures of the kneecap or femur and the bone fragments loose in the joint. The straps around the kneecap can tear. At the same time there is a bruise in the joint. As a result of the effusion, pressure within the joint increases, causing additional pain.

How does the doctor investigate the patellar dislocation?

If the kneecap jumped out, the doctor can usually recognize this at first glance. Often, however, the patella has slipped back into its slide bearing after dislocation, which is referred to as "spontaneous reduction". The doctor must then conclude on the patient's information on a Patellaluxation. By means of certain investigations he checks whether and which accompanying injuries exist.

When an effusion in the knee joint, the patella "floats" on the effusion, so to speak, what is referred to in medicine as a "dancing patella". In the so-called apprehension test, the examiner exerts lateral pressure on the kneecap to the outside. If the patient has pain, this indicates a patellar dislocation.

Apparative diagnosis of patellar dislocation

In addition to the physical examination, it is important to examine the patellar joint and its surrounding structures for possible accompanying injuries and to ensure the diagnosis.Ultimately, this is only possible with the help of imaging techniques. First up is an X-ray. Other methods that can be used are magnetic resonance imaging (MRI) and arthroscopy.

When an effusion in the joint, it makes sense to examine the effusion liquid with a puncture closer. If it is bloody, the straps are often torn. In addition, if there are still fat eyes in the fluid, there is probably a fracture of a bone on the patellar joint.

How to Treat Patellar Luxation

If the kneecap has jumped out and has not spontaneously repaid, it must first be resettled by a doctor as soon as possible. The leg is slowly stretched in the knee and the kneecap carefully guided into its correct position.

If the patient has severe pain, or if the muscles on the leg are cramped, painkillers and tranquilizers can be given.

If it is a first-time, traumatic patellar dislocation and the patient has no other risk factors, then a simple reduction is sufficient as Patellaluxation therapy. After the kneecap has been retracted, the patient usually receives a special orthosis for three to four weeks, which stabilizes the leg in a stretched position. With this splint the full load of the leg is possible.

Read more about the investigations

  • MRI

Surgical procedure for patellar dislocation

The kneecap can usually be restored manually in most cases. However, after only a single patellar dislocation, the risk of further dislocations increases significantly. Therefore, after a second patella excursion, surgery is recommended even without other risk factors. In young, physically active people, surgery is more common than in older patients. Apart from that, accompanying injuries almost always have to be treated surgically.

Ultimately, there are over 100 different surgical techniques for treating patellar dislocation. They all aim to reduce the pull on the kneecap to the outer side of the knee and thereby reduce the risk of dislocation. Today, an arthroscopic procedure is sufficient for a number of procedures, in which the knee is operated on through small accesses (keyhole technique).

Read more about the therapies

  • orthosis

The prognosis of a patellar luxation

The best results are achieved by combining different surgical procedures, for example by shifting the point of attachment of the patellar tendon further inwards and at the same time strengthening the inner tether. Nonetheless, even with optimal treatment, recurrent patellar dislocation may occur, especially if the surgery was delayed.

Due to the possible cartilage damage, osteoarthritis at the patellar joint may occur earlier.

Especially younger patients often go to the doctor only after several dislocations. However, then the kneecap may already be damaged. Therefore, it is important to always go to the doctor when the kneecap has jumped out, even if it restricts on its own. Targeted muscle building training can be a renewed Patellaluxation counteract.


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