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A protruding kneecap (patella) or kneecap dislocation is called patellar luxation. The kneecap jumps out of its slide bearing and usually shifts outwards. It is one of the most common injuries to the knee and mainly affects young athletic people. There are two types of patella luxations, which are differentiated according to their cause. First, the kneecap may pop out due to an accident-related trauma; mostly young people are affected. On the other hand, the kneecap dislocation can occur due to the system without a previous event. In the following, the symptoms, the causes, the diagnosis and the forms of therapy with the kneecap popped out are explained.
Definition of patellar luxation
A popped knee (luxation of the patella) denotes an injury to the knee joint in which the kneecap jumps out of its plain bearing and usually shifts outwards. It is not uncommon for the inner ligaments of the knee to tear or tear.
Kneecap jumped out - symptoms
The kneecap is a flat, V-shaped and free-running bone in front of the knee joint, which protects it and on the one hand reduces the friction of the four-headed thigh muscle and on the other hand increases its leverage, so that the maximum extension of the knee is made possible. The kneecap is connected to the knee joint capsule by tendons, ligaments and muscles. When the knee moves, it slides up and down in a plain bearing on the thigh bone (femur) that fits normally. Due to the high forces that occur in the kneecap joint and a joint guide that is only stabilized by tendons, ligaments and muscles, the kneecap may pop out due to various causes.
Patellar dislocation is very painful, with the knee pain being most severe below the knee and on the inside of the kneecap, and immediately recognizable by a typical deformation of the knee. In addition, severe swelling of the knee joint can occur due to a joint effusion if bleeding occurs due to ligament injuries. As a result, there is usually a restricted movement of the knee. In some cases, small cartilage or pieces of bone break out due to the patellar luxation, which can become trapped in the joint and later damage the cartilage and osteoarthritis in the knee.
Athletes are particularly affected by a trauma-related dislocation of the kneecap, for example, if the affected person is given a powerful kick against the knee while the leg is stretched and the thigh muscles are not or are not tight. As a result, soccer players are more likely to suffer from patellar luxation. Sometimes crash accidents can cause the kneecap to pop out.
If the kneecap pops out without a previous accident, it is usually a system-related cause. This can be the case, for example, if the plain bearing, in whose "track" the patella normally runs, is too flat. A malformed patella (patella dysplasia) itself or a raised patella, which can often be attributed to an accident, are also possible. Other system-related causes of patella dislocation can include the X-legs (genu valgum), a patella shift to the opposite side and a general weakness of the connective tissue.
The risk factors for the kneecap jumping out primarily relate to the possible causes caused by the system. Since women are affected more often than men, female gender is one of the risk factors for patellar luxation. A general weakness of the connective tissue, malalignment of the axis as it occurs with X-legs, malformations of the kneecap or its plain bearing, disorders or weaknesses of the hamstring muscles as well as accident or system-related kneecap elevation are also included. In addition, sports such as soccer pose an increased risk of knee injuries.
If a kneecap jumps out of its slide bearing, it usually moves outwards. This can be seen from a gaze diagnosis based on the typical deformation of the knee. Often, the kneecap repositions itself spontaneously, so that manipulation is no longer necessary. Sometimes an examination of the medical history is necessary if, for example, no accident or trauma has preceded the patellar luxation. If necessary, measures are necessary to prevent the kneecap from jumping out again.
After the kneecap has returned to its starting position either by itself or through manipulation, a joint effusion is often visible and palpable. The areas on the inside of the kneecap and on the outer edge of the slide channel on the thigh are usually sensitive to pressure and painful. In a so-called apprehension test, the doctor pushes the kneecap slightly outwards to provoke renewed patellar luxation and thereby find out whether the patient's kneecap had previously jumped out. If this is the case, the patient resists pressing because he already knows the feeling, or the kneecap can be moved beyond the plain bearing.
Further examinations can be carried out using x-rays, magnetic resonance imaging (magnetic resonance imaging, MRI) or arthroscopy (joint mirroring). With the latter, small pieces of joint or cartilage can be removed and joint irrigation performed.
Patellar luxation treatment
In order to avoid consequential damage, the treatment of a patella luxation should take place as early as possible. In most cases, the kneecap will automatically return to its original position. However, if the patella luxation persists, it must be moved back into the plain bearing by manipulation by a doctor. Similar to shoulder dislocation, the risk of renewed patellar dislocation increases with each further dislocation of the kneecap. Although there is no causative conservative form of therapy, appropriate muscle training and wearing certain orthoses can reduce the risk of further incidents of this kind.
If a joint effusion occurs, a puncture may also be necessary, which not only drains the blood but also contributes to pressure relief and pain relief.
If the kneecap jumps out again or if there is cartilage or bone damage, an operation may be necessary. Depending on the cause and type of complaint, different procedures can be used. A capsule gathering or patella restraint is often performed, so that the path of the kneecap is predetermined and stabilized during movements.
Naturopathy and holistic medicine
If the kneecap pops out once or more often, a visit to the osteopath can be useful and provide information about the cause, which, from an osteopathic point of view, can affect all structures that influence the statics of the body. In this way, all factors are examined and, if necessary, treated, which can lead to tension on or around the patella. An example is the iliotibial tract, a tendon that runs from the outer knot of the tibia, where it connects to the lateral tether of the patella, and continues along the thigh. The so-called Chapman points, treatment points that correspond to the intestine, lie on the tract. Since the same nerves supply parts of the intestine here, interactions are assumed in osteopathy. (No)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Dipl. Social Science Nina Reese
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- V.B. Duthon: Acute traumatic patellar dislocation; in Orthopedics & Traumatology: Surgery & Research; Volume 101, Issue 1, Supplement, February 2015, sciencedirect.com
- F.J. Schneider, A. Thumfart, W.E. Linhart: treatment of patella luxation in childhood and adolescence; in Arthroscopy, February 2009, Volume 22, Issue 1, pages 60-67, springer.com