Perthes disease – Diagnostics – Overview of Information and Clinical Research

Diagnosing Perthes disease requires careful observation of symptoms and specialized imaging tests to understand what is happening inside a child’s hip joint. Early and accurate diagnosis is essential because it helps doctors decide on the best approach to protect the hip during the years-long healing process.

Introduction: Who Should Undergo Diagnostics

Parents should seek medical evaluation if their child begins to limp, especially if the limping appears without an obvious injury or accident. Children with Perthes disease often start limping before they notice any pain, which can make it easy to dismiss the symptoms as something minor like growing pains.^[1] The limp may come and go at first, appearing more noticeably when the child is tired.^[6]

It is also important to consult a doctor if a child complains of persistent pain in the hip, groin, thigh, or knee. Sometimes the pain from a hip problem shows up in a different location, a phenomenon known as referred pain.^[1] Many children with Perthes disease feel discomfort in their knee rather than their hip, which can be confusing for parents trying to understand the source of the problem.^[3]

Children who show stiffness or reduced movement in the hip joint should also be evaluated. This stiffness may become more apparent during physical activities or when the child tries to spread their legs apart.^[4] If a child experiences worsening pain and limping over time, or if the symptoms do not improve with rest and basic home care, medical attention is necessary.^[1]

⚠️ Important

Any child who complains of ongoing hip pain, develops a limp without injury, or shows difficulty moving the hip should be seen by a healthcare professional. Early diagnosis can make a significant difference in the long-term outcome of Perthes disease. If your child has a fever or cannot bear weight on the leg at all, seek emergency medical care immediately.

Classic Diagnostic Methods

Diagnosing Perthes disease begins with a thorough conversation between the doctor and the family. The doctor will ask when the symptoms first appeared, what makes them better or worse, and whether there are any other health concerns.^[4] Understanding the child’s medical history helps the doctor form an initial picture of what might be happening inside the hip joint.

After taking the medical history, the doctor performs a physical examination. This involves moving the child’s legs through different positions to see which movements cause pain or stiffness.^[4] The doctor will check the child’s range of motion, looking particularly at how far the hip can rotate inward and how well the child can spread the legs apart, a movement called abduction.^[3] Limited movement and pain during these tests can suggest a problem with the hip joint.

X-rays

X-rays are the most common and essential tool for diagnosing Perthes disease. However, initial X-rays taken soon after symptoms begin may appear completely normal. It can take one to two months after symptoms start for the characteristic changes of Perthes disease to become visible on X-ray images.^[9] This delay happens because the bone changes gradually as the condition progresses through its stages.

As the disease advances, X-rays reveal changes in the shape and density of the femoral head, which is the ball-shaped top of the thigh bone. The femoral head may appear smaller, less round, or fragmented, as if it is breaking into pieces.^[2] Doctors often recommend taking X-rays at multiple time points to track how the disease is progressing and how the bone is healing.^[9]

Magnetic Resonance Imaging (MRI)

An MRI scan uses magnets and radio waves to create detailed images of the bones and soft tissues inside the body. MRI is particularly valuable in the early stages of Perthes disease because it can detect bone damage and changes in blood supply before these problems show up on X-rays.^[9] This early detection can be crucial for starting treatment at the right time.

MRI scans provide a clearer picture of how much of the femoral head is affected by the loss of blood supply. This information helps doctors understand the severity of the condition and make better decisions about treatment options.^[9] However, MRI is not always necessary for every child with Perthes disease. Doctors decide whether to order an MRI based on the individual child’s situation and the information they need.

Bone Scan

A bone scan is another imaging test that may be used to diagnose Perthes disease. During this test, a small amount of radioactive material is injected into the child’s bloodstream. This material travels to the bones and shows up on special cameras, revealing areas where bone is actively growing or healing, as well as areas where blood supply is reduced.^[4] A bone scan can help identify the affected area and assess the extent of bone damage.

Ultrasound

Ultrasound uses sound waves to create images of the inside of the body. While it is not the primary tool for diagnosing Perthes disease, ultrasound can be helpful in certain situations. It can detect fluid buildup or inflammation in the hip joint, which often accompanies Perthes disease.^[4] Ultrasound is painless and does not use radiation, making it a safe option for children.

Blood Tests

Blood tests do not diagnose Perthes disease directly, but they play an important role in ruling out other conditions that can cause similar symptoms. For example, infections or inflammatory conditions affecting the hip can cause pain and limping just like Perthes disease.^[4] Blood tests help doctors confirm that the symptoms are not caused by an infection or another medical problem that requires different treatment.

Hip Arthrography

Hip arthrography is a specialized imaging procedure that involves injecting a contrast dye into the hip joint while the child is under anesthesia. After the dye is injected, the doctor moves the hip and takes X-ray images or uses a fluoroscopy machine to watch the hip joint in real time.^[16] This procedure helps doctors see how well the femoral head fits into the hip socket and whether there is stiffness or tightness in the surrounding tissues.

Arthrography is particularly useful for assessing whether the hip is properly contained within the socket. If the femoral head is extruding or pushing out of the socket, this can lead to poor healing and deformity.^[11] The information from arthrography helps doctors decide whether surgery or other interventions are needed to reposition the hip for better healing.

⚠️ Important

Perthes disease can look similar to other hip conditions in children. Doctors use multiple diagnostic tests not only to confirm the diagnosis but also to distinguish Perthes from infections, other forms of bone death, or genetic bone disorders. If both hips are affected, additional testing may be needed to rule out conditions like multiple epiphyseal dysplasia.

Diagnostics for Clinical Trial Qualification

When children with Perthes disease are being considered for enrollment in clinical trials, specific diagnostic tests are used to determine eligibility. Clinical trials are research studies that test new treatments or approaches to managing the disease. These studies have strict criteria to ensure that participants are at the right stage of the disease and that researchers can accurately measure whether the experimental treatment is working.

Standard X-rays are essential for clinical trial qualification. Researchers use X-rays to assess the stage of the disease, the amount of femoral head involvement, and the shape of the hip joint.^[9] Classification systems help describe how much of the bone is affected and where the damage is located. This detailed assessment determines whether a child’s condition matches the specific requirements of a clinical trial.

MRI scans may also be required as part of the screening process for clinical trials. MRI provides precise information about the extent of bone death and the condition of the cartilage and soft tissues around the hip.^[9] This detailed imaging allows researchers to select participants whose disease characteristics align with the goals of the study.

Hip arthrography might be used in some clinical trials to assess how well the femoral head is contained within the hip socket. Trials testing new surgical techniques or bracing methods often need this information to measure treatment success.^[16] The results of arthrography help determine whether a child’s hip anatomy is suitable for the intervention being studied.

Blood tests and other laboratory evaluations may be part of the screening process to ensure that participants do not have other medical conditions that could interfere with the trial or make participation unsafe. For example, blood tests can rule out infections, metabolic disorders, or other health issues that might affect bone healing.^[4]

Clinical trials may also require baseline measurements of pain, mobility, and quality of life. These assessments are not diagnostic tests in the traditional sense, but they provide important information about how the disease is affecting the child’s daily life. Researchers use these measurements to track improvements or changes during the trial and to evaluate whether the new treatment makes a meaningful difference for participants.

Enrollment in clinical trials often depends on the child’s age and the stage of the disease. Some trials focus on children in the early stages of Perthes disease, while others may include children with more advanced disease or those who have residual deformities after the bone has healed.^[13] Diagnostic tests help researchers identify participants who are at the right point in their disease journey to benefit from the experimental treatment being tested.

Prognosis and Survival Rate

Prognosis

The long-term outlook for children with Perthes disease varies significantly depending on several key factors. Age at diagnosis is one of the most important predictors of outcome. Children who are diagnosed before the age of six generally have a very good prognosis, with most healing well regardless of treatment.^[16] Younger children have more time for their bones to remodel and grow, which helps the femoral head regain a rounder shape even after significant damage.

Children diagnosed between the ages of six and eight have more variable outcomes. Some do very well with appropriate treatment, while others may develop hip deformities that cause problems later in life.^[16] Children older than eight at the time of diagnosis tend to have poorer outcomes because they have less remaining growth time for the bone to reshape itself.^[13] Girls with Perthes disease tend to have more severe outcomes than boys, although the condition is much more common in boys.^[12]

The extent of femoral head involvement also affects prognosis. Children with less than half of the femoral head affected generally do better than those with more extensive damage.^[10] If the femoral head extrudes or pushes out of the hip socket during healing, this increases the risk of permanent deformity and early arthritis.^[11]

Most children with Perthes disease eventually recover and can return to normal activities after eighteen to twenty-four months of treatment, though the complete healing process can take two to five years.^[2] However, if the femoral head does not heal in a round shape, some children may develop degenerative arthritis in mid-adult life, typically in their forties or fifties.^[3] Without proper treatment, the risk of early arthritis requiring hip replacement surgery increases significantly.

Survival rate

Perthes disease is not a life-threatening condition. All children with this condition survive, and it does not affect life expectancy.^[1] The disease specifically affects the hip joint and does not spread to other parts of the body or cause systemic illness. While the condition can be painful and limiting during the active disease phase, and may lead to long-term hip problems if not properly managed, it does not pose any risk to a child’s life. The focus of treatment is on preserving hip function and preventing complications that could affect quality of life in adulthood, not on survival.

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