Patellar Dislocation

If the kneecap has slipped out of its V-shaped slide bearing, this is referred to as a luxating patella. With a frequency of about 6:100,000, patellar dislocations are one of the most common knee joint injuries.

Patellar Dislocation

What is a patellar dislocation?

A luxation of the patella is a dislocation (luxation) of the kneecap (patella), in which the patella has usually jumped laterally (to the outside) out of the bony guide channel or its sliding bearing on the thigh bone (femur). See foodanddrinkjournal for Hepatitis B Dictionary Definitions.

Additional ligaments, bones and cartilaginous structures in the affected knee are often injured. Patellar dislocation presents in most cases with pain in the front of the knee, a lack of extension, joint effusion, and tenderness on the lateral condyle (joint process) and medial retinaculum (retaining ligament) of the femur.

In addition, a distinction is made between initial dislocations as a result of external trauma (impact, blow, fall) and post-traumatic chronically recurrent as well as habitual patellar dislocations without existing trauma. In rare cases, congenital (congenital) dislocations of the kneecap can be identified.


Depending on the specific triggering cause, different forms of patellar luxation are distinguished. In the case of a habitual dislocation, an instability of the kneecap results from a hereditary malformation of the plain bearing, the retaining ligaments, muscles and/or knee joint capsule.

In addition, acquired dispositions such as an enlargement of the Q-angle, a flat articular process of the femur, patella alta (kneecap elevation), genu recurvatum (high knee), atrophy of the stabilizing muscles, femoral antetorsion are associated with an increased risk of patellar dislocation.

Reduced blood flow and bone necrosis in the area of ​​the knee joint, especially on the plain bearing or on the patella, can lead to impairment of the adjacent cartilaginous structures, thus to instability of the patella and corresponding dislocations. In addition, external trauma or twisting accidents during sporting activities can cause the kneecap to slip out of its guide groove (traumatic luxating patella).

Symptoms, Ailments & Signs

The most noticeable and characteristic symptom of a ruptured kneecap is sudden, severe pain when moving. This is particularly noticeable below the knee and on the inside of the knee. Due to the severe pain, those affected can no longer move their lower legs and cannot put weight on their legs.

They usually adopt a gentle posture automatically. As a result, a distinctive deformation of the knee is immediately recognizable from the outside. Paralysis rarely occurs. In a few cases, the kneecap is so badly dislocated that it can only be brought back into its original position by using force.

Those affected can feel the kneecap slipping away. In addition, there may be visible swelling of the knee if joint effusions also occur. Sometimes bruises can be seen on the skin if there is bleeding from injuries to the ligaments. In such cases, there is also clearly audible pressure pain.

Various bone fractures and cartilage injuries can occur with a luxating patella, which cause a number of other symptoms. Pressure or movement pain can also be felt in other areas of the affected leg. If the kneecap spontaneously slides back on its own, the knee usually remains swollen. The pain can be perceived as weakened for the time being.

Diagnosis & History

As a rule, a patellar dislocation, in particular an acute traumatic dislocation, can be diagnosed on the basis of the characteristic symptoms.

The diagnosis is backed up by an X-ray, which also allows statements to be made about congenital causes and accompanying bone or cartilage injuries. Above all, a so-called patella défilée recording, a target recording with increasing flexion, is used to evaluate the patella lateralization and possible cartilage damage (chondropathy). In the course of an arthroscopy, uncertain cases can be ruled out and minor cartilage and bone damage can be surgically removed at the same time.

Magnetic resonance tomography (MRI) is used for a more precise assessment of the cartilage damage and possible impairments of other soft tissues of the knee. If there is a joint effusion, a puncture should be performed to rule out concomitant injuries. In the long term, retropatellar arthrosis (joint wear and tear) can be expected in many cases after a patellar dislocation despite a good prognosis, since the previous stability of the kneecap cannot be restored even with consistent therapy.


Dislocation of the kneecap usually occurs when the patella is dislocated. This complaint is very painful, causing severe pain, especially in the knees. This pain can also spread to other parts of the body. Furthermore, the knee pain at night can lead to sleep disorders and thus to irritability of the person concerned.

Patients also suffer from an effusion on the knee and severe swelling due to the luxating patella. Difficulty walking and restricted mobility are also part of the clinical picture. Many everyday activities are therefore only possible with difficulty, so that in many cases those affected are dependent on the help of other people in their lives. The pain of patellar dislocation can be limited with the help of medication.

Long-term use of painkillers, however, can damage the stomach. Likewise, the affected person is usually dependent on therapy in order to achieve complete healing. In severe cases, the cartilage can also be damaged in the patellar dislocation. An operation is usually necessary to remove the destroyed cartilage.

When should you go to the doctor?

If optical changes in the knee joint are noticed, a doctor should be consulted. If sudden pain or displacement of the kneecap occurs after a fall or accident, a doctor is needed. Restrictions in the range of motion or a low load-bearing capacity of the knee must be examined and treated. In some cases, bone irregularities appear after an unfortunate twisting of the leg or during the performance of sports and other physical activities. As soon as they are noticed, a relieving posture should be assumed and the activity should be stopped. Sensitivity disorders, paralysis of the leg or problems with blood circulation must be presented to a doctor.

Swelling, discoloration of the skin and sensitivity to pressure are signs of health problems. To avoid permanent damage while moving, it is advisable to see a doctor. If the kneecap is displaced without a triggering momentum, a doctor is also required. The cause of the symptoms must be determined so that an optimal treatment plan can be drawn up.

Hobbles, misalignments of the body or incorrect loads must be corrected by seeking medical help. Otherwise there is a risk of lifelong damage and restrictions to the musculoskeletal system. Trouble sleeping, pain at rest, or irritability should be presented to a doctor. Taking pain medication is only advisable after consulting a doctor, as there can be numerous complications.

Treatment & Therapy

The primary measure in the event of a luxated patella is repositioning (“resetting”) the kneecap, which can also take place with painkillers if the pain is severe. The further therapeutic measures for patellar dislocations depend on the extent and causal trigger of the instability.

As part of a conservative therapy, habitual patellar dislocations can be treated with physiotherapy in the case of less pronounced deviations in shape to build up and strengthen the stabilizing muscles (especially the Vastus medialis muscle). If no improvement in symptoms is observed after 3 to 6 months, surgical measures such as capsular cleavage, arthroscopic transection of the retinaculum, or knee capsular lift to correct the shape deviations should be considered.

In the case of traumatic luxations of the patella, small deviations in shape are also initially treated conservatively. If these are accompanied by a tear in the joint capsule and/or bleeding, arthroscopic irrigation followed by physiotherapy is recommended. If the cartilage has split off or the medial patella-femoral ligament has ruptured, the cartilage fragments should be surgically attached and the ligament stabilizing the patella replaced with autologous material in a minimally invasive manner.

If the instability of the kneecap is caused by cartilage damage, the treatment is usually conservative with protection of the affected knee and, if necessary, anti-inflammatory medication. In the case of advanced cartilage wear, the triggering focus can be drilled antegrade or retrograde to restore normal blood flow. To avoid so-called “joint mice” (loose joint bodies), it may be necessary to surgically remove necrotic cartilage material. If necessary, a mosaic plastic (cartilage transplant) can be considered.

Outlook & Forecast

The prognosis of a patellar dislocation is generally favorable. If the health problems arise as a result of an accident, the kneecap is repositioned in a conservative treatment. This is followed by drug therapy to relieve existing pain. Normally, the patient is discharged from treatment within a few weeks as symptom-free.

Many patients also receive physiotherapeutic support. Motion sequences are optimized so that existing complaints are alleviated and health irregularities are prevented from reoccurring.

In severe cases, an operation is necessary. Surgery increases the risk of complications. Sudden discrepancies can also occur in the subsequent wound healing process. Under optimal conditions, the procedure runs smoothly. During the healing phase, physiotherapeutic support is also provided. A recovery can be expected in these patients within six months.

If irreversible damage to the cartilage or the surrounding areas of the knee is documented, the prognosis worsens. Those affected can experience lifelong mobility impairments. Coping with everyday life and carrying out sporting activities are then restricted. As a result, mental disorders can occur due to the emotional stress. There is also the possibility that professional tasks can no longer be sufficiently fulfilled.


In the case of congenitally caused deviations in shape within the knee joint, prophylactic measures to reduce the risk of luxating the patella are only possible to a limited extent. A consistent build-up training of the stabilizing thigh muscles can, however, prevent a redislocation of the kneecap.


In most cases, those affected with a luxated patella have only a few or only limited follow-up measures available. First and foremost, those affected must consult a doctor early on so that there are no further complications or a further deterioration of the symptoms. An early diagnosis usually has a very positive effect on the further course of the disease.

In most cases, patients are dependent on taking various medications that can relieve the symptoms. Those affected should pay attention to the prescribed intake in order to limit the symptoms accordingly. In the event of side effects or if anything is unclear, consult a doctor first.

Furthermore, in the case of patellar dislocation, physiotherapy or physiotherapy measures may also be necessary to alleviate the symptoms. Many of the exercises can also be repeated at home, speeding up healing. Regular check-ups by a doctor are also very important so that further damage can be recognized and treated early on. The luxating patella does not usually limit the life expectancy of the affected person.

You can do that yourself

If there are complaints in the knee joint after a fall or accident, the person concerned should consult a doctor as soon as possible. He needs medical care because the damage to the knee joint cannot be sufficiently regenerated during the self-healing process of the organism.

In the case of a luxated patella, the person concerned should take sufficient care of himself and his body. Cooling compresses also help with swelling. Physical stress or overexertion should be avoided. The movement sequences must be optimized so that as few complaints or consequences as possible occur. One-sided physical strain and poor posture should be compensated for immediately if possible. It is helpful to restructure the completion of everyday tasks. The support of people from the immediate environment should be taken advantage of.

So that the skeletal system and the joints are stressed as little as possible, overweight should be avoided as a matter of principle. The weight should be in the normal range of the BMI. If you are overweight, it is important to change your lifestyle and diet. Excess weight can be reduced by eating a balanced diet rich in vitamins. In addition, the consumption of harmful substances such as nicotine or alcohol should be avoided.

In principle, close cooperation with a doctor and physiotherapist is advisable for this disease. This ensures that the healing process runs optimally.