Patellar luxation

Carola Felchner is a freelance writer in the medical department and a certified training and nutrition advisor. She worked for various specialist magazines and online portals before becoming a freelance journalist in 2015. Before starting her internship, she studied translation and interpreting in Kempten and Munich.

More about the experts All content is checked by medical journalists.

In the case of a patellar luxation, the kneecap (patella) has "jumped out" of the knee joint. It is then no longer in the middle, but is shifted to the side. Sufferers have severe pain and can no longer move their lower leg. The dislocated kneecap often slides back into its starting position on its own. Nevertheless, a patellar dislocation should always be examined by a doctor and treated if necessary. But first aid is due. Read here what it looks like!

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. M22S83

Brief overview

What to do in the event of a patellar luxation? Calm down the affected person, immobilize the leg, cool if necessary, take the affected person to the doctor or call an ambulance
Patellar dislocation risks: Injury to surrounding structures (such as ligaments, bones); painful bruise in the joint; Inability to move the lower leg
When to the doctor In principle, every patellar dislocation should be assessed and treated by a doctor.

Caution!

Never try to correct a popped kneecap yourself. You would very likely make the injury worse.
Never place ice cubes or cool packs directly on the skin to cool the knee, but always with at least one layer of fabric in between. Otherwise there is a risk of local frostbite.
If the joint cartilage is damaged during the patellar dislocation, this can promote premature joint wear (osteoarthritis).
Even with optimal treatment, renewed patellar dislocations cannot be ruled out. This is especially true if the operation was late.

Patellar luxation: what to do?

A patellar dislocation is very painful - and often a shock for those affected: If your own kneecap suddenly protrudes from the side of the leg as a bump, it can be very frightening. It is all the more important that you act courageously as a first aid provider if someone's kneecap has jumped out. What you should be doing is:

Reassure them and explain everything you are doing. That creates trust.
Remove tight-fitting clothing in the joint area (pants). In the event of a dislocation, the area around the joint usually swells up considerably.
Relieve the knee, that is: sit down if the person is not already sitting. Often people with a dislocation instinctively take a gentle posture in which the pain subsides a little. Do not then force the person into a different position.
Very important: do not move your knee if possible! Otherwise you could damage the surrounding ligaments, muscles and nerves!
If possible, cool the swollen area (e.g. with Coolpack). This can relieve some of the bruising, swelling, and pain.
Take the person to the doctor as soon as possible or call an ambulance. This also applies if the kneecap has slipped back into the joint by itself.

Patellar luxation: risks

If the kneecap has popped out, a bruise usually forms quickly in the joint. This increases the pressure inside the joint, which increases the pain.

Occasionally, in the course of a patellar dislocation, smaller pieces of bone can break off from the kneecap or thigh bone. The bone fragments then float loosely in the joint. The straps around the kneecap can also tear.

Patellar luxation: when to see a doctor?

If the kneecap has jumped out, it should be adjusted as soon as possible by a doctor. Even if she has straightened out by herself, a doctor is necessary: He can check whether the surrounding structures were damaged during the dislocation.

Patellar luxation: medical examinations

The doctor usually recognizes at first glance whether the kneecap has jumped out. Sometimes, as soon as the doctor examines the patient, it slipped back into the starting position on its own ("spontaneous reduction"). Then the doctor can draw conclusions about a patellar dislocation based on the patient's information.

Physical examination

The doctor uses certain examinations to check whether the knee joint is actually dislocated. One example is the so-called apprehension test. The doctor exerts lateral pressure on the kneecap outwards. If the patient shows a defensive stance or if the thigh muscle (quadriceps) reacts intensely, this is a sign of a dislocation.

Imaging procedures

They help to examine the kneecap joint and its surrounding structures for possible accompanying injuries. An X-ray examination is primarily used. In some cases, magnetic resonance imaging (magnetic resonance imaging, MRI) or arthroscopy is also necessary.

Joint puncture

If there is an effusion in the joint, a puncture can be useful. The doctor takes effusion fluid with a hollow needle. This relieves the joint and at the same time makes it possible to analyze the fluid more precisely. If it's bloody, it often indicates torn straps. If there are also greasy eyes in the effusion fluid, a bone in the area of the kneecap joint is probably also broken (fracture).

Patellar luxation: Treatment by the doctor

Manual adjustment (repositioning) is usually sufficient therapy for a patellar dislocation if the kneecap has jumped out for the first time and through the application of force (traumatic patellar dislocation). The doctor slowly extends the leg in the knee and carefully guides the kneecap into its correct position. Before doing this, he can give the patient a pain reliever and sedative.

As soon as the kneecap is back in place, the patient is usually given a special splint (orthosis) for three to four weeks. This stabilizes the leg in the stretched position. With this splint you can put full weight on your leg.

Surgical procedure for patellar luxation

If the doctor does not manage to adjust the knee joint manually and / or there are accompanying injuries, an operation is necessary. The same applies if the kneecap has popped out several times. Because the more frequently a joint dislocates, the more unstable the support structures become. During an operation, the doctor can tighten it again and stabilize the joint.

Ultimately, there are over 100 different surgical techniques for treating patellar dislocation. They all have the goal of reducing the tension on the kneecap to the outer side of the knee and thus reducing the risk of dislocation. A so-called arthroscopic procedure is sufficient for a number of procedures today. The knee is operated on through small accesses in the tissue (keyhole technique). The best results can be achieved by a combination of different surgical procedures.

Doctors operate more often on young, physically active people with patellar dislocation than on older patients.

Prevent patellar luxation

The most effective measure to prevent patellar dislocation is targeted training for the muscles that stabilize the knee. This is especially important if someone has risk factors for such a dislocation. Such risk factors are:

History of patellar dislocation: If a kneecap has already popped out, the likelihood of a new dislocation is increased. Because every dislocation and the associated stretching or injury to surrounding structures makes the joint more unstable.
female gender: Patellar luxation occurs particularly often in young, slim female athletes.
Knock knees: Due to the misalignment of the axis, the lateral pull on the kneecap is stronger than normal. This favors a dislocation.
congenital malformations of the kneecap or the kneecap bearing
Congenital or accident-related elevation of the kneecap
Weakness or imbalance in the extensor muscles in the thigh
Systemic diseases with weak connective tissue: For example, the hereditary diseases Marfan syndrome and Ehlers-Danlos syndrome favor patellar luxation.

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