CONGENITAL DISLOCATION OF THE PATELLA

Congenital dislocation of the patella is a medical condition where the knee cap (patella) is not in its normal position at birth. It is caused by a malformation of the knee joint or the muscles and ligaments that support the knee cap. The patella may become dislocated laterally, medially, or superiorly and cause pain, instability, and difficulty moving the knee.

The severity of this condition can range from mild to severe. In certain cases, the patient may require surgery or physical therapy, to manage symptoms and improve knee function.

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Congenital Dislocation of the Patella

Congenital Dislocation of Patella (CDP) is a birth defect. Unfortunately, the kneecap (patella) is abnormally positioned and is not properly aligned with the knee joint. This condition can result in knee pain, instability, and limited range of motion. It is a rare condition that is usually diagnosed in childhood and may require surgical treatment to correct.

Congenital dislocation of the patella is linked to several medical conditions. Notably, diastrophic dysplasia is one such condition, characterized by skeletal abnormalities. Additionally, arthrogryposis, which involves joint contractures, is also associated.

People with Down syndrome may experience this dislocation, alongside individuals diagnosed with Rubinstein-Taybi syndrome, which affects development and growth. Nail-patella syndrome, known for its effects on nails and bones, can also play a role.

Other associated conditions include Larsen syndrome, which presents with multiple joint dislocations, and Ellis-van Creveld syndrome, typically influencing bone development. Each of these conditions may share a connection to congenital patellar dislocation in unique ways.

Etiology and Causes

One specific cause of this condition is the failure or improper development of fetal myotomes. Myotomes are groups of muscle fibers that embryonic cells form during development. When these myotomes do not develop correctly, it can lead to structural abnormalities, affecting the stability and positioning of the kneecap.

By understanding both the broader and more specific causes, we gain a clearer picture of how congenital dislocation of the patella can develop, allowing for better diagnosis and treatment strategies.

QUESTIONS AND ANSWERS

What is Congenital Dislocation of the Patella in a child, and how does it occur?

Congenital Dislocation of the Patella is a condition present at birth where the kneecap (patella) is located abnormally, usually dislocated or unstable. It can occur due to a variety of factors, including abnormal development of the quadriceps muscles, ligaments, or bone structure in the knee joint during fetal development. Genetic factors may also play a role in its occurrence.

What are the common symptoms and signs of Congenital Dislocation of the Patella in a child?

Children with Congenital Dislocation of the Patella may exhibit signs such as an abnormal alignment or position of the kneecap, instability or dislocation of the kneecap with movement, difficulty in straightening the leg, and possible limping or an abnormal gait. As the child grows and becomes more active, they may experience recurrent pain, stiffness, or limited mobility in the affected knee. These symptoms can vary in severity from mild to more severe cases.

How do doctors diagnose and treat Congenital Dislocation of the Patella in a child ?

Diagnosis of Congenital Dislocation of the Patella typically involves a thorough physical examination, imaging studies (e.g., X-rays, MRI), and sometimes additional specialized imaging like CT scans to assess the alignment and anatomy of the knee joint. Treatment depends on the severity of the condition and may include conservative measures like physical therapy to strengthen the muscles around the knee, bracing, or orthotics. In more severe cases, doctors may recommend surgical intervention to correct the alignment of the patella, repair ligaments, or address any other structural abnormalities.

When congenital medical problems arise, the experts are at the Medical City Children’s Orthopedics and Spine Specialists. We urge you to make an appointment

Symptoms

Children with Congenital Dislocation of the Patella may exhibit signs such as an abnormal alignment or position of the kneecap, instability, or dislocation of the kneecap with movement, difficulty in straightening the leg, and possible limping or an abnormal gait.

At birth, clinical findings can be subtle due to the small size and character of the knee structures being examined. A careful examination might reveal:

A hypoplastic patella dislocated laterally, resting adjacent to the lateral femoral condyle
An empty trochlear groove
Knee flexion contracture, which is the inability to achieve full active extension
A tibia positioned in valgus with external rotation, contingent on the severity of the deformity

As the child grows and becomes more active, they may experience recurrent pain, stiffness, or limited mobility in the affected knee. These symptoms can vary in severity from mild to more severe cases.

Additionally, if the flexion deformity exceeds 90 degrees, the lateralized extensor mechanism may function as a flexor, affecting the child’s movement. Associated conditions, such as hip and foot deformities like club foot or vertical talus, often coexist, further impacting mobility.

In older children, the presentation can be more subtle, often marked by delayed ambulation, weak quadriceps, and anterior knee pain. These developmental changes highlight the importance of early recognition and intervention to manage the condition effectively.

Diagnosing a Congenital Dislocation of Patella

Doctors diagnose Congenital Dislocation of the Patella (CDP) by performing a physical examination and imaging tests. During the physical exam, the doctor will assess the knee’s range of motion, and stability, and look for any signs of deformity. Imaging tests, such as X-rays or MRI scans, are used to confirm the diagnosis and to determine the extent of the condition. Furthermore, these tests help doctors see the position of the patella. Additionally, they disclose any other underlying skeletal problems that may contribute to the dislocation.

In some cases, doctors may also request additional tests. For instance, a CT scan, to get a more detailed view of the knee joint and surrounding structures. The diagnostic process may also involve consultations with orthopedic surgeons and other specialists to determine the best course of treatment.

Why Choose Ultrasound Over Radiographs for Diagnosing Congenital Dislocation of the Patella in Young Children?

When it comes to diagnosing congenital dislocation of the patella in younger children, ultrasound often takes precedence over traditional radiographs. Here’s why:

Incomplete Bone Development: In young children, the patella and surrounding areas often haven’t fully ossified. This means that bones aren’t completely formed, making it hard for radiographs to provide accurate images. Ultrasound excels here by showing detailed pictures of both soft and developing bony tissue.
Non-Invasive and Safe: Ultrasounds are non-invasive and free from radiation exposure. This makes them a safer option for small children who require frequent monitoring.
Real-Time Imaging: Ultrasound offers the advantage of real-time imaging. This allows healthcare providers to assess joint movement and alignment dynamically, providing a clearer picture of joint issues.
Easy Accessibility: Ultrasound machines are typically more accessible, especially in clinics and non-specialized medical facilities. This makes it easier to perform timely and cost-effective examinations.

By leveraging the capabilities of ultrasound, healthcare professionals can ensure more accurate, safe, and efficient diagnosis of congenital dislocation of the patella in young children.

Clinical Findings of Congenital Dislocation of the Patella at Birth

Identifying congenital dislocation of the patella at birth requires careful examination due to the often subtle nature of the condition. Below are some key observations:

Knee Abnormalities: A newborn’s knee may present with a patella that is underdeveloped (hypoplastic) and positioned laterally, next to the lateral femoral condyle.
Trochlear Groove: The trochlear groove, typically housing the patella, may appear empty.
Knee Motion: There may be a flexion contracture, which implies difficulty or inability to fully extend the knee actively.
Tibial Position: The tibia could exhibit a valgus alignment with external rotation, varying with the severity of the defect.

Additionally, while the quadriceps muscle might still contract voluntarily, allowing potential full knee extension, a flexion contracture over 90 degrees may cause the lateralized extensor mechanism to function more like a flexor.

Associated Conditions

It is common for hip and foot deformities to accompany this condition, including club foot or vertical talus.

Observations in Older Children

In older children, more subtle symptoms may include delayed walking capabilities, weak quadriceps, and anterior knee pain.

Each of these findings is significant in diagnosing congenital dislocation of the patella early in life, aiding in timely intervention and management.

Why Choose Ultrasound Over Radiographs for Diagnosing Congenital Dislocation of the Patella in Young Children?

When it comes to diagnosing congenital dislocation of the patella in younger children, ultrasound often takes precedence over traditional radiographs. Here’s why:

Incomplete Bone Development: In young children, the patella and surrounding areas often haven’t fully ossified. This means that bones aren’t completely formed, making it hard for radiographs to provide accurate images. Ultrasound excels here by showing detailed pictures of both soft and developing bony tissue.
Non-Invasive and Safe: Ultrasounds are non-invasive and free from radiation exposure. This makes them a safer option for small children who require frequent monitoring.
Real-Time Imaging: Ultrasound offers the advantage of real-time imaging. This allows healthcare providers to assess joint movement and alignment dynamically, providing a clearer picture of joint issues.
Easy Accessibility: Ultrasound machines are typically more accessible, especially in clinics and non-specialized medical facilities. This makes it easier to perform timely and cost-effective examinations.

By leveraging the capabilities of ultrasound, healthcare professionals can ensure more accurate, safe, and efficient diagnosis of congenital dislocation of the patella in young children.

Treating a Congenital Dislocation of the Patella

The treatment for Congenital Dislocation of the Patella (CDP) depends on the severity of the condition and may include non-surgical and surgical options.

Non-surgical options include:

Physical therapy: To improve knee strength, flexibility, and stability, a physical therapist may develop an exercise program.
Bracing: Wearing a knee brace can help support the knee and improve stability.
Medications: Anti-inflammatory medications can help relieve knee pain and swelling.

Surgical options include:

Soft tissue surgery: To correct the position of the patella, doctors can surgically adjust the ligaments. This often involves procedures like extensive lateral release, which allows for the centralization of the patella and quadriceps. Techniques such as iliotibial band release and lateral capsulotomy are commonly used. In cases of valgus subluxation of the tibia, biceps femoris lengthening may also be necessary.
Osteotomy: In severe cases, doctors may need to cut and reposition the bones of the knee. This can be supplemented with posterior capsule release if there is a significant knee flexion contracture. These adjustments aim to correct alignment and enhance joint function.
Joint reconstruction: In some cases, surgeons will rebuild the knee joint to improve its stability and function. This can involve V-Y quadricepsplasty, z-lengthening, or even femoral shortening if the extensor mechanism is shortened and cannot be centralized. Imbrication of the redundant medial capsule might be performed to stabilize the patella.

Additionally, a medial patellofemoral ligament reconstruction may be considered to support the medial imbrication. When the patellar tendon insertion is excessively lateral, surgeons might perform a distal realignment with a Roux-Goldthwait transfer or complete medialization of the patellar tendon.

For more complex cases, surgical treatment is often necessary. This typically involves several specialized techniques:

Extensive lateral release:

This procedure allows the centralization of the patella and quadriceps, involving:

Iliotibial band release
Lateral capsulotomy
Biceps femoris lengthening if there is valgus subluxation of the tibia
Posterior capsule release: This may be considered if there is a significant knee flexion contracture.
V-Y quadricepsplasty, z-lengthening, or femoral shortening: These techniques may be necessary if the extensor mechanism is shortened and cannot be centralized.
Imbrication of the redundant medial capsule: This helps stabilize the patella, and a medial patellofemoral ligament reconstruction may supplement the medial imbrication.
Distal realignment: If the patellar tendon insertion is excessively lateral, a Roux-Goldthwait transfer or complete medialization of the patellar tendon may be performed.

The most appropriate treatment option for a patient with CDP will depend on their individual case. Doctors will determine the best procedure after a thorough exam, ensuring the surgical approach is tailored to the specific needs and anatomical considerations of the patient.

Surgical Goals for Treating Congenital Dislocation of the Patella

The primary objectives of surgery for congenital dislocation of the patella are focused on realigning and stabilizing the knee. These goals include:

Realignment of the Patella: The patella, or kneecap, needs to be correctly positioned within the trochlear groove. This groove is a natural indentation at the end of the femur, where the patella normally rests and moves. Proper alignment ensures that the patella functions efficiently during movement.
Medialization Procedures: This involves repositioning the patella towards the center of the body. By doing this, surgeons aim to improve knee mechanics and reduce the risk of further dislocations or misalignments.
Addressing Anterior Thigh Structures: It’s often necessary to adjust the structures in the front of the thigh. This might involve lengthening or reconstructing muscles and tendons to enhance the overall stability of the knee joint. Lengthening can provide more flexibility and accommodate the repositioned patella.

These surgical interventions are crucial for improving functionality, alleviating pain, and preventing future dislocations, ultimately enhancing the quality of life for individuals with this condition.

Potential Complications Following Surgery for Congenital Dislocation of the Patella

When undergoing surgery for congenital dislocation of the patella, patients might face several potential complications. These issues can vary in severity and impact recovery and overall knee function.

Patellofemoral Dislocation: After surgery, the kneecap may continue to dislocate either inward (medially) or outward (laterally), which can complicate healing and normal activities.
Extensor Lag: Difficulty in fully straightening the leg can occur, which is often referred to as extensor lag. This condition can affect walking and knee stability.
Joint Stiffness: Reduced mobility in the knee joint post-surgery is a common challenge, making physical therapy crucial for regaining full movement.
Peroneal Nerve Palsy: There’s a risk of peroneal nerve injury, which may lead to weakness or loss of sensation in the lower leg and foot, affecting gait.

Understanding these potential complications helps in preparing for postoperative care and setting realistic recovery expectations. Regular follow-up with healthcare providers and adhering to rehabilitation protocols are essential for minimizing these risks.

Congenital Dislocation of the Patella can be Helped with Physical Therapy

Physical therapy can help in managing symptoms and improving function in individuals with Congenital Dislocation of the Patella (CDP). Moreover, physical therapy can help improve knee strength, stability, and flexibility, which can reduce pain and improve overall function. A physical therapist will work with the patient to develop an individualized exercise program that takes into account the patient’s specific needs and goals. This may include exercises to strengthen the muscles around the knee, improve range of motion, and improve overall stability.

In some cases, physical therapy and other treatments, such as bracing or surgery will optimize the patient’s recovery and outcome. Physical therapy is an important component of a comprehensive treatment plan for individuals with CDP and can help improve their overall quality of life.

How Long is the Recovery Period for Surgically Repairing a Congenital Dislocation of the Patella

The recovery period after surgical repair of a Congenital Dislocation of the Patella (CDP) varies depending on the type of surgery performed, the patient’s age, and their overall health. In general, patients can expect to undergo a period of rehabilitation following surgery, which may last several months. During this time, patients will typically need to limit their activities to allow the knee to heal and regain strength. Physical therapy will play an important part in the rehabilitation process. The therapist will work with the patient to develop an individualized exercise program to help regain strength and mobility.

Finally, for most patients, it may take several months to a year to fully recover and return to normal activities. Some patients may experience some limitations in knee mobility and strength, even after a successful surgical procedure. The exact length of the recovery period will depend on the specifics of the patient’s case and the doctors will discuss those elements with the patient and their doctor.

Bring your child to Medical City Children’s Orthopedics and Spine Specialists

Through a combination of preventive measures, regular exercise, and ongoing monitoring, our doctors at Medical City Children’s Orthopedics Spine Specialists can support children in overcoming hamstring contracture and fostering their optimal musculoskeletal health. Also, we have offices in Arlington, Dallas, Flower Mound, Frisco, and McKinney. Give us a call and make an appointment for your child.

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Footnote:

National Library of Medicine: Congenital Dislocation of the Patella

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