7 Key Signs and Symptoms of Perthes Disease (Legg-Calve-Perthes Disease)

Legg-Calve-Perthes disease, commonly known as Perthes disease, is a rare childhood condition affecting the hip joint. It occurs when the blood supply to the rounded head of the femur (thighbone) is temporarily disrupted, causing the bone tissue to die and break down. This condition typically affects children between the ages of 4 and 10 years old, with boys being more commonly affected than girls. Early recognition of symptoms is crucial for proper management and better outcomes. Understanding the warning signs can help parents and caregivers seek timely medical attention for their children.

The disease progresses through several stages, and symptoms may develop gradually over weeks or months. While the exact cause remains unknown, recognizing the symptoms early can significantly impact the child’s recovery and long-term hip function. Below are the most common symptoms associated with Perthes disease that every parent should be aware of.

1. Limping (The Most Common Early Sign)

Limping is often the first noticeable symptom of Perthes disease and may be the primary reason parents seek medical evaluation. The child may develop a noticeable limp that comes and goes, particularly after physical activity or by the end of the day.

The limp occurs because the child tries to minimize weight-bearing on the affected hip due to discomfort or pain. Initially, the limp may be subtle and painless, which is why it’s sometimes overlooked or attributed to minor injuries or growing pains. However, as the condition progresses, the limp typically becomes more pronounced and persistent.

Parents should pay attention to:

• Changes in walking pattern, especially after rest periods
• Favoring one leg over the other
• Increased limping after physical activities like running or playing sports
• Limping that persists for more than a few days without improvement

2. Hip Pain and Discomfort

Pain in the hip region is a hallmark symptom of Perthes disease, though interestingly, not all children experience significant pain in the early stages. When pain does occur, it is typically felt in the groin area, along the inner thigh, or directly over the hip joint.

The pain characteristics include:

• Dull, aching sensation that may worsen with activity
• Intermittent pain that comes and goes throughout the day
• Pain that improves with rest but returns with movement
• Discomfort that gradually increases over weeks or months

The pain occurs because the dying bone tissue and subsequent inflammation in the hip joint irritate the surrounding structures. As the femoral head begins to collapse and reshape, mechanical stress on the joint increases, leading to more persistent discomfort. Some children may experience pain primarily during weight-bearing activities, while others may feel discomfort even at rest, especially as the disease progresses.

3. Knee or Thigh Pain (Referred Pain)

One of the most confusing aspects of Perthes disease is that children often complain of pain in the knee or thigh rather than the hip itself. This phenomenon is called “referred pain,” where the problem originates in the hip joint but the pain is felt in other areas along the same nerve pathways.

Many children with Perthes disease will point to their knee as the source of discomfort, which can lead to misdiagnosis or delayed diagnosis if healthcare providers don’t examine the hip joint thoroughly. The referred pain typically affects:

• The inner thigh region
• The front or side of the thigh
• The knee joint area, particularly on the inner side
• The lower groin extending down toward the knee

This is why any child presenting with persistent knee pain without an obvious knee injury should also have their hip evaluated to rule out Perthes disease and other hip conditions.

4. Limited Range of Motion in the Hip

As Perthes disease progresses, children typically develop a restricted range of motion in the affected hip joint. This limitation becomes more noticeable as the femoral head deteriorates and the body tries to protect the joint from further damage.

The range of motion restrictions typically include:

• Reduced internal rotation: The child has difficulty turning the leg inward while the hip is bent
• Limited abduction: Difficulty spreading the legs apart or moving the affected leg away from the body’s midline
• Decreased flexion: Trouble bringing the knee up toward the chest
• Stiffness: General tightness in the hip area, especially after periods of inactivity

Parents may notice these limitations during everyday activities such as putting on shoes and socks, sitting cross-legged, or during sports activities. The child might struggle with movements that were previously easy, like climbing stairs, getting in and out of cars, or participating in activities that require hip flexibility.

5. Leg Length Discrepancy

As the femoral head collapses and reshapes during the disease process, some children develop a noticeable difference in leg length. The affected leg may appear shorter than the healthy leg, creating an asymmetry that contributes to limping and postural changes.

This leg length discrepancy occurs because:

• The collapse of the femoral head effectively shortens the bone structure on the affected side
• Muscle spasms and contractures around the hip can pull the femur upward, creating an apparent shortening
• The body may adapt by tilting the pelvis, which changes the functional leg length

The difference in leg length may be subtle at first, perhaps only a few millimeters, but can become more pronounced as the disease progresses. Parents might notice that their child’s pants appear uneven at the hem, or that the child stands with one hip higher than the other. In some cases, the child may walk on their toes on the affected side to compensate for the leg length difference.

6. Muscle Atrophy (Thigh Muscle Wasting)

Children with Perthes disease often develop noticeable muscle wasting or atrophy in the thigh of the affected leg. This occurs because the child naturally reduces the use of the painful hip, leading to decreased muscle activity and subsequent muscle loss over time.

The muscle atrophy typically affects:

• The quadriceps muscles on the front of the thigh
• The gluteal muscles of the buttock
• The calf muscles, to a lesser extent

When comparing both legs, parents may notice that the affected thigh appears visibly thinner or smaller in circumference than the healthy leg. The skin may appear looser, and the muscle definition is reduced. This atrophy can develop relatively quickly—within weeks to months—especially if the child significantly reduces weight-bearing activities on the affected side.

Muscle atrophy not only affects appearance but also contributes to weakness and reduced function of the leg. The weakened muscles provide less support to the hip joint and can impact the child’s balance, coordination, and ability to perform physical activities.

7. Stiffness and Reduced Activity Level

Children with Perthes disease often experience general stiffness in the hip area, particularly after periods of rest or in the morning upon waking. This stiffness is the body’s protective response to joint inflammation and damage, and it typically improves somewhat with gentle movement but never fully resolves until the condition is treated.

Associated changes in activity level include:

• Decreased participation in sports: The child may voluntarily withdraw from activities they previously enjoyed, such as soccer, running, or gymnastics
• Preference for sedentary activities: Increased time spent sitting or engaging in low-impact activities
• Difficulty with prolonged walking: Tiring more easily during walks or requesting to be carried
• Reluctance to play actively: Avoiding playground equipment, running with friends, or participating in physical education classes

Parents might notice that their once-active child becomes unusually quiet during playtime or makes excuses to avoid physical activities. The child may not explicitly complain about pain but simply shows less enthusiasm for activities that stress the hip joint. This behavioral change is often a coping mechanism to avoid discomfort, and it’s an important symptom that shouldn’t be dismissed as mere laziness or personality change.

Main Causes of Perthes Disease

While the exact cause of Legg-Calve-Perthes disease remains unclear, researchers have identified several factors that may contribute to the development of this condition:

Disrupted Blood Supply: The primary mechanism behind Perthes disease is a temporary interruption of blood flow to the femoral head. Without adequate blood supply, the bone tissue dies (a process called avascular necrosis or osteonecrosis). Why this interruption occurs is not fully understood, but it appears to be the triggering event for the disease process.

Genetic Factors: There appears to be a hereditary component to Perthes disease. Children with a family history of the condition have a higher risk of developing it, suggesting that certain genetic factors may make some individuals more susceptible to blood supply problems in the hip.

Abnormal Blood Clotting: Some studies have found that children with Perthes disease may have abnormalities in blood clotting factors. These clotting problems could potentially lead to small blood clots that temporarily block the tiny blood vessels supplying the femoral head.

Repetitive Trauma: Minor, repetitive trauma to the hip joint may contribute to the development of Perthes disease in susceptible children. This doesn’t mean a single injury causes the condition, but rather that accumulated microtrauma over time might compromise blood flow to the femoral head.

Environmental and Demographic Factors: Certain risk factors have been associated with higher incidence of Perthes disease, including being male (boys are 4-5 times more likely to develop the condition), age between 4-10 years, small stature for age, exposure to secondhand smoke, and lower socioeconomic status. However, these are associations rather than direct causes.

Developmental Factors: Some researchers believe that the blood supply to the femoral head goes through vulnerable periods during childhood development, making it more susceptible to disruption during certain age ranges.

Prevention Strategies

Unfortunately, because the exact cause of Perthes disease is not fully understood, there are no guaranteed methods to prevent its occurrence. However, parents and caregivers can take certain steps to promote overall hip health and potentially reduce risk factors:

Promote General Health: Ensuring children maintain a healthy weight, eat a balanced diet rich in calcium and vitamin D for bone health, and get regular physical activity can support overall musculoskeletal development.

Avoid Secondhand Smoke Exposure: Since exposure to secondhand smoke has been associated with increased risk of Perthes disease, maintaining a smoke-free environment around children is advisable.

Early Detection: While not strictly prevention, being alert to early symptoms and seeking prompt medical evaluation when a child develops a persistent limp, hip or knee pain, or reduced activity level can lead to earlier diagnosis and intervention. Early treatment may help minimize complications and improve long-term outcomes.

Appropriate Activity Modification: If a child is diagnosed with Perthes disease, following medical advice regarding activity restrictions is crucial to prevent further damage to the hip joint during the healing process.

Regular Pediatric Check-ups: Routine well-child visits allow healthcare providers to monitor growth and development and potentially identify hip problems in their early stages.

It’s important to note that Perthes disease is not caused by anything the parent or child did wrong, and in most cases, it cannot be prevented. The focus should be on early recognition and appropriate management rather than prevention.

Frequently Asked Questions

At what age does Perthes disease typically appear?

Perthes disease most commonly affects children between 4 and 10 years old, with peak incidence around age 5-7 years. It rarely occurs in children younger than 2 or older than 12 years.

Is Perthes disease painful?

Pain levels vary among children. Some experience significant hip, groin, thigh, or knee pain, while others have minimal discomfort. Even when pain is mild, other symptoms like limping and limited range of motion are typically present.

Does Perthes disease affect both hips?

Perthes disease usually affects only one hip (unilateral), occurring in about 85-90% of cases. However, approximately 10-15% of children develop the condition in both hips (bilateral), though typically not at exactly the same time.

How long does it take for Perthes disease to heal?

The healing process for Perthes disease typically takes 2-5 years, progressing through several stages: initial stage with blood supply interruption, fragmentation stage where bone breaks down, reossification stage where new bone forms, and finally the healing stage where bone reshapes. Younger children generally have better outcomes and may heal more quickly.

Can a child with Perthes disease walk normally?

During the active phase of the disease, most children develop a limp and may have difficulty with normal walking. With appropriate treatment and management, many children eventually regain normal or near-normal walking ability, though this depends on the severity of the condition and the age at diagnosis.

Will my child need surgery for Perthes disease?

Not all children with Perthes disease require surgery. Treatment decisions depend on the child’s age, the extent of bone involvement, and the shape of the femoral head. Younger children (under 6 years) with mild involvement often do well with observation and activity modification alone, while older children or those with more severe disease may benefit from surgical intervention to improve hip joint alignment.

What activities should be avoided with Perthes disease?

High-impact activities that place significant stress on the hip joint are typically restricted during the active phase of the disease. This includes running, jumping, contact sports, and activities involving repetitive impact. Your child’s doctor will provide specific guidance based on the severity of the condition and the stage of healing.

Can Perthes disease cause long-term problems?

Some children may experience long-term effects, including hip stiffness, leg length discrepancy, or an increased risk of developing hip arthritis in adulthood. However, many children, especially those diagnosed and treated early, achieve good functional outcomes with minimal long-term complications. Regular follow-up with an orthopedic specialist is important for monitoring hip development.

Is Perthes disease hereditary?

While Perthes disease does appear to have a genetic component, with a higher risk among children who have family members with the condition, it is not inherited in a simple, predictable pattern. Most children with Perthes disease have no family history of the condition.

When should I seek medical attention for my child?

Consult a healthcare provider if your child develops a persistent limp lasting more than a few days, complains of ongoing hip, thigh, or knee pain, shows reduced activity level or reluctance to participate in physical activities, or demonstrates stiffness or limited movement in the hip area. Early evaluation is important for proper diagnosis and management.

References:

• Mayo Clinic – Legg-Calve-Perthes Disease
• American Academy of Orthopaedic Surgeons – Legg-Calve-Perthes Disease
• Johns Hopkins Medicine – Legg-Calve-Perthes Disease
• Boston Children’s Hospital – Legg-Calve-Perthes Disease
• National Center for Biotechnology Information – Legg-Calve-Perthes Disease