If the kneecap has slipped out of its v-shaped sliding bearing, this is called a patellar luxation. With an incidence of about 6 in 100,000, patellar luxations are one of the most common injuries to the knee joint.
What is a patellar luxation?
Patellar luxation refers to a dislocation (luxation) of the kneecap (patella) in which the patella has usually jumped laterally (to the outside) out of the bony guide groove or its sliding bearing on the thigh bone (femur). Additional ligaments, bones and cartilaginous structures in the affected knee are often injured. In most cases, a patellar dislocation manifests itself as pain in the anterior region of the knee, an extension deficit, joint effusion, and pressure pain on the lateral condyle (articular process) and medial retinaculum (retaining ligament) of the femur. In addition, a distinction is made between first dislocations due to external trauma (impact, blow, fall) and post-traumatic chronic recurrent and habitual patellar dislocations without existing trauma. In rare cases, congenital (congenital) dislocations of the patella can be detected.
Causes
Various forms of patellar luxation are distinguished depending on the specific triggering cause. In habitual luxation, instability of the patella results from a congenital malformation of the sliding bearing, the retaining ligaments, muscles, and/or knee joint capsule. In addition, acquired dispositions such as an increase in the Q-angle, a flat articular process of the femur, a patella alta (raised patella), genu recurvatum (high knee), atrophies of the stabilizing musculature, femoral torsions are associated with an increased risk of patellar luxation. Reduced blood flow as well as bone necrosis in the area of the knee joint, especially at the sliding bearing or at the patella, can lead to an impairment of the adjacent cartilaginous structures, thus to an instability of the patella and accordingly to luxations. In addition, external trauma or twisting accidents during sports activities can cause the patella to slip out of its guiding groove (traumatic patellar luxation).
Symptoms, complaints, and signs
The most noticeable and characteristic symptom of a popped-out kneecap is sudden, severe pain on movement. This is particularly noticeable below the knee and on the inside of the knee. The affected person can no longer move the lower leg or put weight on the leg due to the severe pain. They usually automatically adopt a gentle posture. As a result, a striking deformation of the knee is also immediately recognizable from the outside. Rarely, paralysis occurs. In a few cases, the patella is so severely dislocated that it can only be returned to its original position by force. The sliding away of the kneecap is noticeable for the affected person. In addition, there may be visible swelling of the knee when joint effusions also occur. Sometimes bruising can be seen on the skin, provided that there is bleeding into the ligaments when they are injured. In such cases, there is also clearly audible pressure pain. Along with patellar luxation, various bone fractures and cartilage injuries can occur, which cause a number of other symptoms. In addition, pressure or movement pain may 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 may thus be perceived as attenuated for the time being.
Diagnosis and course
In all cases, patellar dislocation, especially acute traumatic dislocation, can be diagnosed on the basis of characteristic symptoms. The diagnosis is confirmed by a radiograph, which also provides information about congenital causes and concomitant bone or cartilage injuries. Above all, a so-called patella défilée image, a target image taken under increasing flexion, is used to evaluate patellar laterization and possible cartilage damage (chondropathy). During arthroscopy, uncertain cases can be excluded and at the same time minor cartilage and bone damage can be surgically repaired. Magnetic resonance imaging (MRI) is used for a more precise assessment of cartilage damage and possible impairment of other soft tissues of the knee.If necessary, a puncture should be performed in the case of a joint effusion to exclude concomitant injuries. In the long term, retropatellar arthrosis (joint wear) is to be expected after patellar luxation in many cases, despite a good prognosis, because the previous stability of the patella cannot be restored even with consistent therapy.
Complications
Usually, patellar luxation results in dislocation of the kneecap. This complaint is very painful, so there is a lot of pain, especially in the knees. This pain can also spread to other regions of the body. Furthermore, the knee pain can lead to sleep problems at night and thus irritability of the affected person. Likewise, due to patellar luxation, patients suffer from an effusion on the knee and severe swelling. The clinical picture also includes walking difficulties and restricted mobility. Many activities of everyday life are thus 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 luxation can be limited with the help of medication. However, long-term use of painkillers can damage the stomach. Likewise, the affected person usually relies on therapy to achieve a complete recovery. In severe cases, patellar luxation can also damage the cartilage. In this case, surgery is usually necessary to remove the destroyed cartilage.
When should you see a doctor?
If visual changes in the knee joint are noticed, a visit to the doctor should be made. If sudden pain or displacement of the kneecap occurs after a fall or accident, a doctor is needed. Restrictions in range of motion or low weight-bearing capacity of the knee should be examined and treated. In some cases, the irregularities of the bone structure occur after an unfortunate twisting movement of the leg or during the practice of sports as well as other physical activities. As soon as they are noticed, a gentle posture should be adopted and the activity should be stopped. Sensitivity disorders, paralysis of the leg or problems with blood circulation should be presented to a doctor. Swelling, discoloration of the skin and sensitivity to pressure are signs of health impairment. To avoid permanent damage to locomotion, a doctor’s visit is advised. If there is a displacement of the kneecap without a triggering momentum, a doctor is also needed. The cause of the discomfort must be determined so that an optimal treatment plan can be developed. Limping, misalignment of the body or incorrect loading must be corrected by seeking medical attention. Otherwise, there is a risk of lifelong damage and limitations to the musculoskeletal system. Sleep disturbances, a pain at rest or irritability should be presented to a doctor. Taking pain medication is not advised until a medical professional has been consulted, as there can be numerous complications.
Treatment and therapy
The primary measure for patellar dislocation is reduction (“setting”) of the kneecap, which can also take place under pain medication if the pain is pronounced. The further therapeutic measures for patellar luxations depend on the extent and causative trigger of the instability. As part of a conservative therapy, habituated patellar luxations with less pronounced form deviations can be treated physiotherapeutically to build up and strengthen the stabilizing muscles (especially the vastus medialis muscle). If no improvement of symptoms can be observed after 3 to 6 months, surgical measures such as a capsular split, arthroscopic transection of the retinaculum, or knee joint capsular retraction to correct the form deviations should be considered. Traumatic patellar dislocations are also initially treated conservatively for minor form deviations. If these are accompanied by a joint capsule tear and/or hemorrhage, arthroscopic irrigation followed by physical therapy is recommended. If cartilage avulsions or ruptures of the medial patellofemoral ligament are present, the cartilage fragments should be surgically attached and the ligament stabilizing the patella should be minimally invasively replaced with endogenous material.If the instability of the kneecap is caused by cartilage damage, conservative treatment is usually given with rest of the affected knee and, if necessary, anti-inflammatory medication. In the case of advanced cartilage wear, the triggering focus can be drilled ante- or retrogradely to restore normal blood flow. To prevent so-called “joint mice” (free joint bodies), it may be necessary to surgically remove necrotic cartilage material. If necessary, mosaicplasty (cartilage grafting) may be considered.
Outlook and prognosis
The prognosis of patellar luxation is generally favorable. If the health complaints arise due to an accident, the kneecap is repositioned in a conservative treatment. This is followed by drug therapy to alleviate existing pain. Normally, the patient is discharged from treatment within a few weeks as symptom-free. Many patients also receive physiotherapeutic support. Movement patterns are optimized so that existing complaints are alleviated and a recurrence of the health irregularities is prevented. In severe cases, surgical intervention is necessary. Surgery increases the risk of complications. Similarly, sudden irregularities may occur in the subsequent wound healing process. Under optimal conditions, the surgery proceeds without any disturbances. Physiotherapeutic support is also provided during the healing phase. Recovery can be expected within six months in these patients. If irreversible damage to the cartilage or surrounding areas of the knee is documented, the prognosis worsens. Affected individuals may experience lifelong impairments in locomotion. Coping with everyday life and performing sports activities are then limited. As a result, psychological disorders may occur due to the emotional stress. Likewise, there is the possibility that occupational tasks can no longer be adequately performed.
Prevention
In the case of congenital form deviations within the knee joint, prophylactic measures to reduce the risk of patellar luxation are only possible to a limited extent. However, consistent strengthening training of the stabilizing thigh muscles can prevent patellar reluxation.
Aftercare
In most cases of patellar luxation, only a few or even limited aftercare measures are available to those affected. First and foremost, those affected must see a doctor early on to prevent further complications or a further worsening of the symptoms. As a rule, early diagnosis always has a very positive effect on the further course of the disease. In most cases, patients are dependent on taking various medications that can alleviate the symptoms. Patients should pay attention to the prescribed dosage in order to limit the symptoms accordingly. In the event of side effects or if anything is unclear, a doctor should be consulted first. Furthermore, in the case of patellar luxation, measures of physiotherapy or physiotherapy may also be necessary to alleviate the symptoms. Many of the exercises can also be repeated at home, which accelerates the healing process. Regular checks by a doctor are also very important so that further damage can be detected and treated at an early stage. The patellar luxation thereby does not usually limit the life expectancy of the affected person.
What you can do yourself
If there is discomfort of the knee joint after a fall or accident, the affected person should consult a doctor as soon as possible. He needs medical care, because the damage to the knee joint can not be sufficiently regenerated during the self-healing process of the organism. In the case of patellar luxation, the affected person should take sufficient care of himself and his body. In the case of swelling, cooling compresses also help. Physical strain or overexertion should be avoided. Movement patterns should be optimized so that as few complaints or sequelae as possible occur. One-sided physical strain and incorrect posture should be corrected immediately if possible. It is helpful to restructure the way in which everyday tasks are performed.Support should be sought from people in the immediate vicinity. To minimize stress on the skeletal system and joints, excess weight should always be avoided. The weight should be in the normal range of the BMI. In the case of existing overweight, a change in lifestyle and diet is important. Excess weight can be lost through 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 physician as well as physiotherapists is advisable for this disease. This can ensure that the healing process proceeds optimally.