Patellar dysostosis is a rare genetic condition that affects how the kneecaps develop and can also affect nearby bones and joints. Many living with patellar dysostosis have small, uneven, unstable, or absent kneecaps, which can lead to knee pain, stiffness, or trouble with walking, running, kneeling, or climbing stairs. It is usually present from birth, but the features of patellar dysostosis may be noticed in childhood or later when movement problems become clearer. Not everyone will have the same experience, and most people with patellar dysostosis have a normal life expectancy unless it occurs as part of a broader syndrome with other health problems. Treatment does not reverse the bone changes, but many people are helped by physical therapy, pain relief, activity changes, braces or supports, and sometimes orthopedic surgery for joint instability.
How many people live with Patellar dysostosis?
Patellar dysostosis is so rare that no reliable worldwide headcount is available; Orphanet lists the condition’s prevalence as unknown rather than giving a global estimate (Orphanet, 2024). The same is true in the United States, where the Genetic and Rare Diseases Information Center says the number of people living with patellar dysostosis is not known (GARD, 2024).
Overview
Patellar dysostosisSymptoms
Patellar dysostosis mainly affects the kneecaps, which may be very small, oddly shaped, or missing. Many living with patellar dysostosis have knee pain, kneecap instability, trouble straightening the leg, or walking differences noticed in childhood.
Outlook and prognosis
For many living with patellar dysostosis, outlook is often good, especially when knee symptoms are mild. Some may have ongoing kneecap instability, pain, or trouble with squatting and stairs. Long-term joint wear can develop in more affected knees.
Causes and risk factors
Patellar dysostosis is usually caused by a genetic change that affects kneecap development before birth. It may run in families or happen for the first time in one child, and lifestyle or environmental factors are not known primary causes.
Genetic influences
Genetics are very important in patellar dysostosis, which is usually caused by changes in genes involved in kneecap and limb development. Many cases run in families, though the exact gene can vary, so genetic testing may help clarify the cause.
Diagnosis
Patellar dysostosis is usually diagnosed from clinical features seen on exam and imaging findings, especially knee X-rays. Genetic tests may help confirm the diagnosis of Patellar dysostosis and check for related inherited conditions.
Treatment and drugs
Treatment for patellar dysostosis focuses on comfort, knee stability, and mobility. Many living with patellar dysostosis benefit from physical therapy, activity changes, pain relief, or bracing. If the kneecap is very unstable or painful, orthopedic surgery may help.
Symptoms
Knee problems with stairs, squatting, sports, or getting up from the floor can be one of the first clues to Patellar dysostosis. In daily routines, this might show up as small but noticeable changes. The early features of Patellar dysostosis usually relate to a kneecap that is smaller than usual, shaped differently, unstable, or sometimes hard to feel at the front of the knee. Some people have mild findings, while others have more obvious limits with knee strength, comfort, and stability.
In Patellar dysostosis, the kneecap may be unusually small, irregular, or hard to feel. Imaging may show that it formed incompletely or sits in an unusual position.
The kneecap can slide out of place or feel as if it is about to shift, especially with stairs, squatting, or quick turns. Repeated slipping can make the knee feel unreliable.
Many living with Patellar dysostosis notice aching or sharp pain at the front of the knee after walking, running, kneeling, or standing up from a chair. Soreness or mild swelling may follow heavier activity.
Deep bending, kneeling, or squatting may be uncomfortable or hard to do fully. Some people avoid sitting low to the ground because getting back up takes extra effort.
How people usually first notice Patellar dysostosis?
The first signs of patellar dysostosis are often noticed in infancy or early childhood, when a baby or young child seems to have unstable knees, delayed walking, trouble fully straightening the leg, or frequent falls. In some children, a doctor first suspects it during a checkup because the kneecaps feel unusually small, oddly shaped, or hard to feel, and an X-ray then shows that the patella, or kneecap, did not develop in the usual way. How patellar dysostosis is first noticed can vary, but for many families it starts with repeated knee giving-way, unusual kneecap appearance on imaging, or concerns about early motor development.
Types of Patellar dysostosis
No distinct types of Patellar dysostosis are widely recognized.
Can I slow down the onset of symptoms?
No, there is no good evidence that lifestyle changes or medicine can meaningfully delay the start of symptoms in patellar dysostosis, because this is a genetic condition where the kneecap develops differently from the start. Staying at a healthy weight, avoiding repeated knee strain, and working with physical therapy may help with pain, stability, and daily movement, but that is about managing symptoms, not preventing the condition or stopping symptoms from appearing. Even so, early support and regular care can often help many living with patellar dysostosis stay more comfortable and active.
What genetics can tell you about symptoms
Genetics can sometimes help explain why people with patellar dysostosis have different symptoms, such as very small or missing kneecaps, knee instability, pain, or trouble fully straightening the leg. Certain inherited gene changes are linked to how the kneecap and nearby bones form, and they may influence how severe the condition is, but they usually cannot predict exactly which symptoms will happen in one person because symptoms can vary even within the same family. In many living with patellar dysostosis, the bone changes are present from birth, although day-to-day problems may become more noticeable in childhood or later as walking, sports, or repeated kneeling put more stress on the knees.
Causes and risk factors
The main causes of patellar dysostosis are gene changes that affect how the kneecap and nearby bones form before birth. These changes may be inherited from a parent or may happen for the first time as a new mutation. Family history is the main known risk factor, and genetic testing can sometimes clarify your personal risk. The exact gene involved can affect how mild or severe it is, and some people have patellar dysostosis as part of a broader inherited bone condition. Body weight, muscle strength, and knee injuries can affect symptoms and function, but lifestyle or environmental factors do not usually cause patellar dysostosis.
What are the most common causes or risk factors?
Patellar dysostosis, which means the kneecap does not form in the usual way, is most often caused by genetic changes that affect bone growth before birth, and the strongest risk factor is having a family history of the condition or a related inherited condition. In some people, it appears along with other birth differences involving the hips, feet, nails, or other bones. There are no well-known lifestyle or everyday environmental risk factors, and it is not usually caused by sports, an injury, or anything a parent did during pregnancy.
Environmental and biological risk factors
Patellar dysostosis is uncommon, and clear risk factors are not mapped out as well as they are for many other birth conditions. Many families searching for what causes patellar dysostosis find that doctors often cannot point to one specific exposure or event. Doctors often group risks into internal (biological) and external (environmental), but for patellar dysostosis the strongest links involve early fetal development, while outside triggers remain uncertain.
Patellar dysostosis starts very early in pregnancy, while the knee and lower limb are still forming. That makes early fetal development the main biological window linked to this condition, even though it is not something parents can see happening day to day.
Patellar dysostosis is more likely to be seen when there are other differences in bone, joint, or limb formation before birth. When doctors notice a wider pattern of skeletal development changes, underdevelopment of the kneecap becomes more likely.
Clear environmental causes of patellar dysostosis have not been firmly identified. Researchers study harmful exposures that can affect fetal development in general, but no specific outside exposure is a well-established risk factor for this condition.
Serious disruptions in the pregnancy environment can affect fetal growth and bone formation overall. Still, direct links between common maternal health conditions and patellar dysostosis have not been clearly proven.
Genetic risk factors
Patellar dysostosis usually happens because of a change in a gene involved in early leg and knee development, most often TBX4. In many living with patellar dysostosis, the change is inherited from a parent, though it can also appear for the first time in a child. Carrying a genetic change doesn’t guarantee the condition will appear, and relatives can be affected in very different ways.
TBX4 changes: The best-known genetic cause of patellar dysostosis is a change in the TBX4 gene, which helps guide how the lower limbs form before birth. Changes in this gene can lead to small, misshapen, or absent kneecaps and may also affect the hips, pelvis, or feet.
Family history: Patellar dysostosis often follows an autosomal dominant inheritance pattern, which means a child may develop it if just one parent carries the gene change. For each pregnancy, the chance of passing that change on is 1 in 2, or 50%.
New changes: Some children with patellar dysostosis have a new genetic change that was not inherited from either parent. This helps explain why the genetic causes of patellar dysostosis may be found even when no one else in the family is known to have it.
Variable features: People with the same genetic change can have very different effects, even within one family. One relative may have clear knee and leg findings, while another has milder changes that are noticed much later.
Lifestyle risk factors
Patellar dysostosis is present from birth, so lifestyle habits do not cause it, but they can influence pain, joint function, and the chance of secondary problems over time. In practice, how lifestyle affects patellar dysostosis often comes down to knee loading, muscle support, body weight, and injury prevention. Daily habits can either reduce stress on an underdeveloped or unstable kneecap or make symptoms harder to manage.
Higher body weight increases force across the kneecap and the front of the knee with walking, stairs, and squatting. In patellar dysostosis, that extra load can worsen pain and make tracking or instability symptoms more noticeable.
Repeated jumping, deep squats, hard running surfaces, and contact sports can place extra stress on a small, malformed, or unstable patella. This may raise the risk of pain flares, giving-way episodes, or cartilage wear over time.
Weak quadriceps, hip abductors, and core muscles can reduce control of knee alignment during movement. Better strength and neuromuscular control may improve patellar tracking and help compensate for structural differences.
Tight hamstrings, calves, or iliotibial band can change knee mechanics and increase pressure around the kneecap. Regular, well-guided stretching may improve movement patterns and reduce discomfort with daily activity.
Risk prevention
For patellar dysostosis, there is no known way to prevent the condition itself because it is usually present from birth and relates to how the kneecap develops. Prevention mainly means lowering the chance of pain, kneecap instability, falls, and joint damage over time. Some people have only mild symptoms, while others may need more support with activity, footwear, or medical follow-up. Prevention is flexible—it adapts to your life and health background.
If patellar dysostosis runs in your family, genetic counseling may help you understand the chance of passing it on. This can be useful before pregnancy or when planning a family.
Low-impact activity and guided strengthening around the hips and thighs can help support the knee and improve stability in patellar dysostosis. Many living with patellar dysostosis do better with swimming, cycling, or physical therapy than with repeated jumping or hard pivoting sports.
Repeated kneeling, deep squats, and high-impact exercise can put extra stress on an already fragile kneecap or knee joint. Protecting the knee during work, sports, and daily tasks may reduce pain and lower the risk of injury.
Good footwear, home safety changes, and balance training can help lower the chance of falls if the knee feels weak or gives way. This matters because unstable knees can lead to sprains, bruising, or worsening joint symptoms.
Can you prevent Patellar dysostosis?
No, patellar dysostosis, a condition where the kneecap does not form in the usual way, cannot usually be prevented. It is generally linked to genetic changes that affect bone development before birth, so there are no proven lifestyle steps that can stop it from happening. If it runs in your family, genetic counseling before pregnancy may help you understand the chances of passing it on, but it cannot prevent the condition itself.
Transmission
Patellar dysostosis is not infectious, so it cannot spread from one person to another through touch, coughing, sex, food, or shared spaces. Instead, the genetic transmission of patellar dysostosis happens through changes in genes that affect how the kneecap and nearby bones develop.
How patellar dysostosis is inherited can vary depending on the exact diagnosis, but some forms run in families in a dominant pattern, meaning a parent with the gene change may pass it on to each child. In other families, it appears for the first time because of a new genetic change, with no earlier history of the condition.
When to test your genes
Consider genetic testing if patellar dysostosis is suspected because of very small or absent kneecaps, knee instability, related limb differences, or a family history of similar findings. Testing is most useful early in life or before pregnancy planning, because it can confirm the diagnosis and help guide orthopedic follow-up and family counseling.
Diagnosis
Patellar dysostosis is usually diagnosed by putting together the pattern of knee features, growth and bone findings, and family history, then confirming the cause with targeted tests. Many living with patellar dysostosis are assessed after delayed walking, kneecap problems, frequent falls, or knee pain draws attention to the joints. Getting a diagnosis is often a turning point toward answers and support.
Doctors look for small, missing, or unstable kneecaps and check how the knees move and line up. They also examine the feet, pelvis, and other bones because patellar dysostosis can occur with a wider pattern of skeletal changes.
A detailed family and health history can help show when knee problems began and whether relatives have had similar features. This part of the diagnosis of patellar dysostosis can also clarify whether symptoms are isolated or part of a broader inherited condition.
Imaging findings often show absent, very small, or unusually shaped kneecaps. X-rays may also reveal changes in the pelvis or lower limbs that support the diagnosis and help rule out other bone disorders.
Genetic tests may be offered when the physical findings suggest an inherited skeletal condition. These tests can confirm the genetic diagnosis of patellar dysostosis in some families and help with counseling about recurrence risk.
How is Patellar dysostosis diagnosed?
Patellar dysostosis, which means the kneecaps do not form normally, is usually diagnosed with a doctor’s exam, a review of symptoms and family history, and imaging tests such as X-rays to show whether the kneecaps are small, uneven, or missing. Doctors may also look for related bone changes in the hips, legs, or feet, since these can help support the diagnosis. If it seems to run in a family or be part of a wider inherited condition, genetic testing may also be offered.
Stages of Patellar dysostosis
Patellar dysostosis does not have defined progression stages. This is because it is usually a difference in how the kneecap develops rather than an illness that steadily worsens over time. Doctors usually start with a conversation about knee symptoms, mobility, and any family history, then confirm the finding with a physical exam and imaging such as X-rays. In many people, patellar dysostosis symptoms are picked up when knee pain, instability, or unusual kneecap shape leads to an orthopedic evaluation.
Outlook and prognosis
The outlook for people with patellar dysostosis is generally good, because the condition is usually nonprogressive and does not affect life expectancy. Prognosis depends mainly on how much the kneecap abnormality alters knee stability, pain, and mobility, with some individuals having few symptoms and others experiencing recurrent dislocation, difficulty with kneeling, or early joint wear. Many people do well with physical therapy, activity modification, pain management, and in selected cases orthopedic surgery to improve alignment or stability. When patellar dysostosis occurs as part of a broader genetic syndrome, long-term outcome is shaped more by the associated features than by the patellar abnormality itself. Mortality is not typically increased by isolated patellar dysostosis.
Long-term effects
For many living with patellar dysostosis, the long-term picture centers on how well the knees stay stable and tolerate everyday movement. Some have mild effects, while others notice more trouble with walking, stairs, kneeling, or sports as the years go on. Long-term effects vary widely, and the outlook often depends on how underdeveloped the kneecap is and whether one or both knees are affected. In adulthood, some may find that wear and tear in the joint becomes more noticeable than the early symptoms of patellar dysostosis were in childhood.
A small, misshapen, or absent kneecap can make the knee feel less steady during walking, turning, or climbing stairs. Over time, this may lead to repeated giving-way episodes or a feeling that the joint does not track smoothly.
Many people with patellar dysostosis have some reduction in knee strength or range of motion. For many, this can mean difficulty with squatting, kneeling, running, or getting up from a low chair.
Long-term strain on the front of the knee can lead to ongoing aching, especially after activity or long periods of standing. Some may have little pain in childhood but notice more discomfort in the teen or adult years.
If the knee does not move in a stable way, gait can stay altered over many years. In children this may show up as delayed motor milestones or awkward stair use, while adults may notice fatigue or a persistent limp.
How is it to live with Patellar dysostosis?
Living with patellar dysostosis can be very different from one person to another, but for many it means dealing with kneecaps that are small, misshapen, or unstable, which can make walking, climbing stairs, kneeling, running, or getting up from a chair more tiring or uncomfortable. Some people have only mild limitations, while others may have repeated knee pain, a feeling that the knee might give way, or trouble with activities that put pressure on the joint, so daily life may involve pacing activity, doing physical therapy, or using supportive braces after medical advice. This can also affect people around you, since family members, teachers, coaches, or coworkers may need to understand that mobility can vary from day to day and that certain physical tasks may need to be modified rather than pushed through.
Treatment and drugs
Treatment for patellar dysostosis focuses on improving comfort, knee stability, and day-to-day movement, since there is no medicine that can correct the way the kneecap developed. Many people with patellar dysostosis do well with a tailored plan that may include physical therapy to strengthen the muscles around the knee, activity changes, and sometimes a brace or support if the knee feels loose or slips out of place. Doctors sometimes recommend a combination of lifestyle changes and drugs, such as pain-relieving medicines when needed, especially if early symptoms of patellar dysostosis include knee pain, giving way, or trouble with stairs. If symptoms are more severe, an orthopedic specialist may discuss surgery to improve kneecap tracking or treat repeated dislocations, and what works best often depends on age, bone structure, and how much the knee is affecting daily life.
Can you cure Patellar dysostosis?
No, patellar dysostosis cannot usually be cured, because the kneecap does not develop in the usual way and treatment cannot fully reverse that. Care is aimed at improving pain, knee stability, and movement, and may include physical therapy, changes in activity, pain relief, and sometimes surgery if problems are more severe. Many people with patellar dysostosis can still improve comfort and day-to-day function with the right support.
Non-drug treatment
Patellar dysostosis can affect walking, stair climbing, kneeling, and sports because the kneecap and nearby joints may not form in the usual way. For many, treatment begins not at the pharmacy, but with practical support to improve movement, protect the knees, and make daily activities easier. Non-drug care is tailored to age, symptoms, and whether there is knee instability, pain, or trouble with other joints. Not every approach works the same way, so care often changes as a child grows or as activity needs shift.
Physical therapy is often a main part of care for people with patellar dysostosis. It can build strength in the thigh, hip, and core muscles, improve balance, and help the knee track more steadily during walking and stairs.
Some may find that kneeling, deep squats, jumping, or high-impact sports make symptoms worse. A therapist or orthopedic specialist can help adjust activities so joints stay active without being pushed in ways that raise the risk of pain or kneecap instability.
Knee braces, sleeves, taping, or shoe inserts may help some people feel more stable during daily movement. These supports do not change the bone shape, but they can reduce strain and make walking or exercise feel safer.
When patellar dysostosis affects more than the knees, occupational therapy can help with dressing, school tasks, hand use, or other everyday activities. Supportive therapies can also suggest adaptive tools and simpler movement patterns that save energy and protect sore joints.
Your genes may have an impact on how drugs work for you
For people with patellar dysostosis, treatment usually focuses on symptoms such as knee pain, joint strain, or surgery-related care, and there is no well-established evidence that the genetic change linked to this condition routinely changes how common medicines work. In everyday life, this means pain relievers, anti-inflammatory medicines, and medicines used around surgery are usually chosen based on age, overall health, and the specific problem being treated, not on this diagnosis alone. Even so, if someone living with patellar dysostosis is having surgery or needs longer-term pain treatment, it is still wise to tell the care team about the diagnosis and any unusual past reactions to medicines.
Pharmacological treatments
There is no specific medicine that corrects patellar dysostosis itself, because the condition involves how the kneecap develops rather than a problem a drug can reverse. When treatment is needed, medicines are usually used to ease pain or inflammation from knee strain, instability, or arthritis that can develop over time. Some medicines work quickly, while others are used only during symptom flare-ups or after procedures. Not everyone with patellar dysostosis needs medication, and choices depend on symptoms, age, and joint changes seen on imaging.
Acetaminophen is often used for mild to moderate knee pain in people with patellar dysostosis. It can help with day-to-day discomfort but does not reduce swelling or fix kneecap instability.
Nonsteroidal anti-inflammatory drugs such as ibuprofen, naproxen, or diclofenac may help if pain comes with swelling or irritation around the knee joint. These are often considered among the first medicines tried for early symptoms of patellar dysostosis when overuse or arthritis is contributing.
Gels or creams such as topical diclofenac can be useful when pain is limited to the knee area. They may ease symptoms with less whole-body exposure than tablets, though skin irritation can happen.
In some cases, corticosteroid injections are used when there is significant joint inflammation or arthritis-related pain. They can provide temporary relief, but repeated injections are usually limited because they do not treat the underlying bone shape.
Genetic influences
For many people with patellar dysostosis, knee symptoms are tied to the way the kneecaps and nearby bones formed very early in development, and this is most often linked to a change in the TBX4 gene. You may notice that patellar dysostosis seems to run in the family, because it is usually inherited in an autosomal dominant pattern, which means one changed copy of the gene can be enough to cause it. A parent with the condition can pass that gene change to a child, although in some families it appears for the first time in one person. Even within the same family, the effects can vary, so one relative may have more noticeable knee, hip, or foot changes while another has milder features. Knowing the genetic cause of patellar dysostosis can help confirm the diagnosis and guide family planning, testing, or genetic counseling for relatives.
Is Patellar dysostosis genetic?
Genetics are very important in patellar dysostosis, which is usually caused by changes in genes involved in kneecap and limb development. Many cases run in families, though the exact gene can vary, so genetic testing may help clarify the cause.
Having a genetic risk is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are common across the general population. Most of these variants do not directly affect health and are simply part of normal human diversity. For many genes, having a variant tied to a condition suggests a possible link rather than a certain diagnosis, especially when several genes and environmental factors are involved. In some cases, though, a single well-understood variant in a particular gene is enough to confirm a diagnosis.
Pharmacogenetics—how genetics influence drug effects
For many living with patellar dysostosis, treatment is aimed at easing knee pain, improving stability, and making everyday movement like climbing stairs, standing up, or walking longer distances feel safer and easier. Patellar dysostosis is often linked to an inherited change in a gene involved in early leg and kneecap development, so genetic testing can help confirm the diagnosis and show whether other family members may also be affected. This usually does not change one specific medicine, because there is no drug that fixes the underlying gene change itself. Genetics is only one factor, and doctors usually choose medicines based on symptoms such as pain or swelling, along with age, joint function, other health conditions, and whether physical therapy, bracing, or surgery is also needed. So when people look into treatment options for patellar dysostosis, the genetic result is often most helpful for diagnosis, family planning, and guiding follow-up, while day-to-day treatment remains focused on symptom relief and joint support.
Interactions with other conditions
Day to day, patellar dysostosis can become more noticeable when another joint problem is present, especially knee arthritis, loose joints, or conditions that affect balance and muscle strength. Someone might notice that climbing stairs, getting up from a low chair, or walking on uneven ground feels harder when knee pain from another cause is added on top. Certain diseases may overlap, meaning a kneecap that is small, misshapen, or unstable can add to symptoms from other bone and joint conditions rather than causing a completely separate set of problems. If patellar dysostosis is part of a broader inherited syndrome, doctors may also check for problems outside the knee, especially kidney disease and glaucoma, because those links come from the underlying syndrome and not just the kneecap change itself. For many living with patellar dysostosis, this means care may involve more than one specialist when early symptoms of knee instability appear alongside other health issues.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Patellar dysostosis?
Patellar dysostosis can look like other conditions that affect the kneecap, especially nail-patella syndrome, a genetic condition that also changes the nails, elbows, and sometimes the kidneys, and small patella syndrome, which can cause very small or missing kneecaps along with changes in the hips and feet. More common knee problems, such as repeated kneecap dislocation or pain from the kneecap not moving smoothly, can also cause similar symptoms like knee pain, a feeling that the knee may give way, or trouble with stairs.
History
For many living with patellar dysostosis, the history of the condition helps explain why it can still take time to recognize. A child may be the first in the family to have knee pain, trouble with sports, or a kneecap that seems unstable, while someone else is only diagnosed after an X-ray done for another reason. Patellar dysostosis did not become widely discussed in medicine all at once; it was pieced together gradually from reports of unusually small, misshapen, or absent kneecaps and related bone findings.
Early doctors usually described what they could see and feel rather than grouping these changes under one clear label. Once considered rare, now recognized as a distinct skeletal finding, patellar dysostosis appeared in older medical reports under broader descriptions of kneecap underdevelopment or congenital knee differences. As imaging improved through the 20th century, doctors became better at telling patellar dysostosis apart from injuries, arthritis, or kneecap problems that develop later in life.
Over time, the way the condition has been understood has changed, and that has been important for patients and families. Researchers learned that kneecap changes could occur on their own or as part of a wider pattern affecting bones elsewhere in the body, which helped make diagnosis more accurate. Later studies also showed that some cases have a genetic basis, even though the day-to-day experience can vary a lot from one person to another.
That shift in understanding matters because the early symptoms of patellar dysostosis can be subtle. Some people mainly notice knee instability when climbing stairs or getting up from the floor, while others have few symptoms until adulthood. Today, the history of patellar dysostosis is less about one dramatic discovery and more about a steady improvement in recognizing a condition that had often been overlooked or grouped with other knee disorders.