Knee dysplasia is a congenital developmental disorder of the skeleton that results from a genetic mutation and is characterized by severe short stature. The prognosis depends on the severity in each individual case. Causal therapies are not yet available.
What is knee dysplasia?
Spondylometaepiphyseal dysplasia manifests in growth and associated gait disturbances from about the second year of life. One dysplasia from this group of diseases is Knee Dysplasia. The condition is also called Kniest syndrome and corresponds to a congenital developmental disorder of the skeletal bones. This severe skeletal dysplasia causes extreme short stature associated with characteristic skeletal changes. The disease is classified as a collagenosis. This group of diseases encompasses systemic diseases with degeneration of connective tissue associated with dysregulation in the immune system and autoantibody formation against endogenous structures. The incidence of knee dysplasia is not known. It was first described by Kniest, a pediatrician, who documented the condition in the late 20th century. Kniest dysplasia has an extremely wide spectrum of severity.
Causes
Knee dysplasia is a genetic disorder of which 200 cases have been documented to date. Familial clustering has been observed in the cases documented to date. Inheritance may be autosomal dominant. However, most of the cases documented so far are new mutations. Type II collagens, which carry secretory defects in patients with Knee syndrome, have now been identified as causative. The defective collagens are due to mutations in the COL2A1 gene. Most of the mutations are structural defects that appear as in-frame mutations. Thus, the cause of the disease is a deletion or splicing mutation of the gene that codes for type II collagens. Most cases of knee dysplasia correspond to a heterozygous new mutation of the COL2A1 gene. To pass on the defect to biological children, patients with the dysplasia have a 50% risk.
Symptoms, complaints, and signs
Patients with knee dysplasia may be affected by a variable spectrum of symptoms that affect prognosis. Clinically, Kniest syndrome presents immediately after birth and is characterized by dysproportional short stature in infancy. The dysproportionality results primarily from shortening of the trunk. Most patients reach an adult height between only 106 and 156 centimeters. In addition to a kyphosis of the thorax, a lumbar lordosis is often present. The patients’ short extremities further exacerbate the dysproportioned appearance. In most cases, Kniest syndrome is also accompanied by distended joints. As the disease progresses, this association often worsens. A flat midface and a widely sunken nasal bridge may be additional symptoms. Around half of all sufferers also have a cleft palate. Hearing loss is equally common. A somewhat rarer symptom is myopia, i.e. nearsightedness of varying severity. In addition, there is often progressive dysplasia of the limb and axial skeleton. Because of the thickening of the bones and the largely immobile joints, some patients are affected by complete inability to walk. Osteoporosis may also be an accompanying symptom of the disease.
Diagnosis and course of the disease
Radiographic findings are generally used to diagnose Kniest syndrome. In addition to deformed epiphyses, radiographs provide evidence of the affected individual’s missing femoral heads, widened femoral metaphyses, platyspondylia, and vertebral anomalies. Histopathologic findings may support the diagnosis by showing inclusions in the chondrocyte cytoplasm or an extremely vacuolated matrix of cartilage. Specific forms of spondyloepiphyseal dysplasia and metatropic dysplasia should be considered as differential diagnoses. Young patients of knee dysplasia in particular often have clinical and radiologic findings that overlap with OSMED findings. Myopia helps in the differential diagnosis to OSMED. In a case, molecular genetic analysis can confirm the diagnosis. If the dysplasia is known in the family, the mutation can also be diagnosed prenatally.Micromelia is detectable by ultrasound from the second trimester. The prognosis for patients with knee dysplasia depends on the severity of their joint and vertebral abnormalities in each individual case. Thus, depending on the severity, the prognosis can vary between lethal and favorable.
Complications
Knee dysplasia usually results in significant limitations in everyday life and in the life of the affected person. Due to the various malformations on the skeleton, movement restrictions and, in most cases, pain occur. The quality of life is greatly reduced by knee dysplasia. Furthermore, patients also suffer from severe short stature. This can lead to teasing or bullying, especially in children, and thus cause severe psychological discomfort or depression. Not infrequently, the parents and relatives of the affected are also affected by psychological complaints, which can usually be treated by a psychologist. Furthermore, the patient also develops myopia and hearing difficulties. Cleft palate is also not uncommon and can limit the aesthetics of the affected person. The joints cannot be moved properly, so that there may be restrictions in everyday life. The affected person may be dependent on the help of other people. Likewise, the mental development of the child may also be disturbed by the knee dysplasia, so that retardation occurs. Causal treatment of knee dysplasia is usually not possible. The disease can only be treated symptomatically. Life expectancy is reduced by this disease in most cases.
When should you see a doctor?
If symptoms such as hearing loss, nearsightedness, or short stature occur, there may be underlying Knee Dysplasia. A doctor must be consulted if serious symptoms occur that significantly affect well-being and quality of life. If the symptoms persist for more than a few days, medical advice is also required. The congenital form of knee dysplasia is usually diagnosed immediately after birth. Treatment is initiated immediately thereafter, and parents are advised to present the child to a physician on a regular basis. If after the initial treatment symptoms reappear, the appropriate medical professional must be consulted. Signs of osteoporosis require clarification by a specialist. Knee dysplasia often takes a severe course and represents a great psychological burden for the child and the parents. For this reason, therapeutic counseling should always accompany the treatment of the deformities and physical complaints. The family doctor or orthopedist can establish contact with a specialist and, if necessary, refer affected family to a self-help group.
Treatment and therapy
Causal therapy is not available to patients with knee dysplasia. Affected individuals can only receive supportive care. The goal of therapy is to maintain patient mobility. Symptomatic treatment designed to achieve this may include, for example, surgical intervention. For example, if hip dislocation is suspected in the near future, this dislocation can sometimes be averted by surgical intervention. During the growth phase, other neurological deficits may occur in addition to myopia. Not only the motor, but also the mental development of the patients can be retarded in this way or in the worst case even stopped. For this reason, close monitoring by a neurologist is recommended during the growth phase. In the case of flexions or displacements of the bones that exceed five millimeters, stabilization is mandatory. This stabilization usually corresponds to a surgical intervention by a surgeon. If signs of retinal detachment are detected, surgical repair is also usually performed. Supportive therapy for dysplasia may extend to the parents of the affected individual, who may receive therapeutic care or genetic counseling, for example.
Outlook and prognosis
As parents of a child suffering from knee dysplasia, you can take action to help the child have a better quality of life. Even before birth, parents can seek psychotherapeutic help to better process and accept the new situation.Contact with other affected families, for example through self-help groups, has proven positive. They get a good overview of what to expect in the future and receive valuable advice for problems in everyday life. After the birth, adequate medical treatment must be provided immediately. For this purpose, it is necessary to see specialists early on and to have any necessary operations performed. After the wounds have healed, it can be clarified with the doctor when physiotherapeutic treatment can be started. The earlier such therapy begins, the better the chances of preserving the existing mobility. Nevertheless, it is advisable to adapt the living environment to the needs of the handicapped or to plan a move to an apartment suitable for the handicapped. If the child needs a walker or a wheelchair later on, it is not necessary to find a solution under time pressure. Regular check-ups with a neurologist reveal bone displacements that require immediate stabilization. Further neurological deficits can also be detected quickly. Through this it is possible to slow down or even stop them.
Prevention
The primary causes of the mutation of the causative gene are not yet known in Knee Dysplasia. For this reason, few preventive measures are available. However, in family planning, potential parents can at least have their genetic risk for offspring with the dysplasia assessed.
Follow-up
In most cases, the options for follow-up care in knee dysplasia are severely limited, with the primary focus in this disease being rapid and, most importantly, early detection of the disease. Therefore, the affected person should ideally see a doctor at the first signs and symptoms of the disease, so that there is no further worsening of the symptoms. In most cases, those affected are dependent on the help and care of other people in their everyday lives. The support of one’s own family in particular has a very positive effect on the further course of the disease. Loving and intensive conversations are also very helpful and can prevent the development of depression or other psychological upsets. Since this disease can also have a negative effect on the eyes of the affected person, a surgical intervention should definitely be performed in case of detachment of the retina. After such an operation, the eyes should be covered and cared for particularly well. If the patient wishes to have children, genetic testing and counseling can be done first to prevent the Knee dysplasia from recurring in the descendants.
This is what you can do yourself
Individuals suffering from knee dysplasia require comprehensive care from physicians and therapists. Parents of affected children should seek support early and also arrange any surgeries as soon as possible. Good preparation gives parents the necessary space after the birth to first come to terms with their own child’s illness. Therapeutic help is usually nevertheless useful, because the knee dysplasia will burden the parents for many years and cause stress that must be worked through. In addition, measures must be taken to enable the child to live as complication-free a life as possible. In most cases, the home must be adapted for the disabled, and aids such as walking aids, a wheelchair or visual aids must also be organized. After a comprehensive examination, the doctor can make a good assessment of what subsequent complaints are to be expected. The affected child should also receive psychological support at the latest in adolescence. Otherwise, the severe mental and physical limitations may lead to the development of psychological suffering. Preventive therapy is necessary in any case to avoid complications of this kind. A close-meshed medical control is always necessary in case of knee dysplasia.
