Herring classification Introduction (What it is)
Herring classification is a radiographic grading system used in pediatric hip care.
It describes how much of the outer (lateral) part of the femoral head has lost height during Legg–Calvé–Perthes disease.
Clinicians use it to estimate prognosis and to support treatment planning.
It is most commonly applied when reviewing plain X-rays of a child’s hip.
Why Herring classification used (Purpose / benefits)
Legg–Calvé–Perthes disease (often shortened to “Perthes disease”) affects the blood supply to the femoral head (the “ball” of the hip joint) in children. Over time, the femoral head can soften, fragment, and change shape before it heals and remodels. Because the condition evolves over months to years, clinicians need a consistent way to describe severity and communicate expectations.
Herring classification is used because it:
- Standardizes severity on X-ray using a shared language (so different clinicians can discuss the same findings).
- Supports prognosis discussions by relating X-ray appearance to the likely final shape of the femoral head (prognosis varies by clinician and case).
- Helps guide treatment selection in combination with age, symptoms, hip range of motion, and other imaging findings.
- Improves communication across orthopedics, sports medicine, radiology, and physical therapy.
In general terms, the problem it helps solve is risk stratification: identifying which hips appear more structurally preserved versus those with more collapse, so follow-up intensity and treatment approaches can be matched to severity.
Indications (When orthopedic clinicians use it)
Orthopedic clinicians typically use Herring classification in scenarios such as:
- Suspected or confirmed Legg–Calvé–Perthes disease in a child
- Baseline staging after diagnostic imaging suggests Perthes disease
- Severity grading during follow-up when the disease enters stages where the classification is most applicable (often when fragmentation is visible on X-ray)
- Care coordination between providers (orthopedics, radiology, physical therapy)
- Documentation for clinical decision-making, second opinions, or research/registry settings (where applicable)
Contraindications / when it’s NOT ideal
Herring classification is not “unsafe,” but it can be not suitable or less informative in certain situations, including:
- Hip conditions other than Perthes disease, such as slipped capital femoral epiphysis (SCFE), hip dysplasia, inflammatory arthritis, fractures, or adult avascular necrosis (different classification systems are used for those problems).
- Very early presentations when the characteristic radiographic changes needed for grading are not yet clear (another approach may be monitoring or using advanced imaging when appropriate).
- Very late presentations when the femoral head has already healed and reshaped, where other outcome-focused systems may be more relevant.
- Poor-quality or non-standard radiographs, where the lateral portion of the femoral head is difficult to see reliably.
- Uncertain staging (for example, if it is unclear whether the hip is in the phase where the grading is intended to be applied), since interpretation can vary by clinician and case.
How it works (Mechanism / physiology)
Herring classification is not a treatment and does not change physiology by itself. Instead, it reflects the biomechanical consequence of Perthes disease on the femoral head.
The underlying principle
Perthes disease involves a period where part of the femoral head loses normal blood supply. During the course of the disease, the bony structure can weaken and lose height, especially under everyday loading (standing and walking). The Herring classification focuses on the lateral pillar, the outer third of the femoral head on an anteroposterior (AP) pelvis or hip X-ray.
The “pillar” idea is a practical way to describe whether the outer portion of the femoral head is still acting like a supportive column. In general terms:
- More preserved lateral pillar height suggests better structural support and a greater likelihood that the femoral head may heal with a more spherical shape.
- More loss of lateral pillar height suggests more collapse and a higher risk of residual deformity (prognosis varies by clinician and case).
Relevant hip anatomy
Key structures involved include:
- Femoral head (capital femoral epiphysis): the ball portion of the hip joint.
- Acetabulum: the socket that articulates with the femoral head.
- Articular cartilage: smooth surface covering the joint.
- Growth plate (physis): present in children; influences remodeling and healing potential.
- Lateral pillar region: the outer part of the femoral head evaluated on X-ray for height preservation.
Onset, duration, and reversibility (what applies here)
Because Herring classification is a descriptor, not an intervention, “onset” and “duration” are not directly applicable. The closest relevant concept is that the grade is typically assigned when radiographic changes are visible, and the appearance can evolve as the disease progresses. Clinicians may re-evaluate classification over time as imaging changes, depending on the stage and clarity of findings.
Herring classification Procedure overview (How it’s applied)
Herring classification is not a procedure performed on the body. It is a structured way to interpret imaging. A typical high-level workflow looks like this:
-
Evaluation / exam
A clinician evaluates symptoms (often limp, hip/groin/thigh/knee pain), hip range of motion, gait, and overall function. History and physical exam help decide whether hip imaging is needed. -
Preparation
Standardized plain radiographs (commonly an AP pelvis view and additional views as clinically indicated) are obtained. Good positioning and image quality matter for consistent interpretation. -
Testing / interpretation
The clinician (often with radiology input) reviews the X-ray and identifies whether the hip shows changes consistent with Perthes disease and whether the hip is in an imaging phase where the classification is typically used.
The femoral head is conceptually divided into thirds, and the lateral pillar height is compared with expected height or with the opposite side when appropriate. -
Immediate checks
The grade is documented (for example, Group A, B, B/C, or C). Clinicians also consider other factors (age, symptoms, range of motion, and other imaging findings) because classification alone does not capture the whole clinical picture. -
Follow-up
Follow-up intervals and additional imaging are determined based on clinical context. The classification may be revisited if imaging evolves or if different clinicians review the case.
Types / variations
Herring classification is commonly described as the lateral pillar classification with the following groups. Exact interpretation can vary slightly by clinician and case, but the core concept is the same: how much lateral pillar height is preserved.
Group A (more preserved lateral pillar)
- The lateral pillar maintains its height without meaningful collapse on the relevant radiographic view.
- In general terms, this suggests relatively better structural preservation.
Group B (partial loss of lateral pillar height)
- The lateral pillar shows some loss of height, but it is not severely collapsed.
- This is often considered an intermediate category.
B/C border group (borderline features)
- Some cases do not fit cleanly into B or C.
- A B/C border category is often used to reflect mixed or borderline features and to acknowledge interpretive limits.
Group C (substantial loss of lateral pillar height)
- The lateral pillar shows marked loss of height, suggesting more extensive collapse.
- This category generally reflects more severe structural involvement on X-ray.
Related systems (commonly discussed alongside it)
While not “types” of Herring classification, clinicians often reference other Perthes-related frameworks for a fuller picture, such as:
- Catterall classification (another radiographic severity system)
- Salter–Thompson classification (often based on subchondral fracture extent in a specific disease phase)
- Stulberg classification (commonly used later to describe the healed/final shape outcome)
Which system is emphasized varies by clinician, institution, and timing within the disease course.
Pros and cons
Pros:
- Provides a clear, commonly used language for Perthes severity on X-ray
- Focuses on a structurally meaningful region (the lateral pillar) linked to femoral head support
- Helps with risk stratification and planning follow-up intensity (varies by clinician and case)
- Useful for communication across teams and for documentation
- Can be applied using widely available imaging (plain radiographs)
- Often discussed in education and training, supporting consistent teaching
Cons:
- Not a diagnosis and not a standalone decision tool; it must be interpreted with clinical findings
- Depends on disease stage and radiographic visibility; may be less useful early or late
- Image quality and positioning can affect grading consistency
- Some cases are borderline, leading to variability between readers (interobserver variability can occur)
- Does not directly measure cartilage, synovitis, or early marrow changes that may be better seen on MRI
- Does not capture patient-specific factors (age, motion, activity limits, and symptoms) that influence outcomes
Aftercare & longevity
Because Herring classification is a way to describe imaging, “aftercare” refers to what commonly happens after a clinician assigns a grade, and “longevity” refers to how the classification is used over time.
Key factors that can affect how the classification relates to outcomes include:
- Severity of femoral head involvement shown on imaging
- Timing within the disease course, since radiographic appearance evolves
- Age and growth potential, which can influence remodeling capacity (varies by clinician and case)
- Hip range of motion and gait mechanics, which affect functional impact and may influence management decisions
- Follow-up consistency, including repeat exams and imaging when indicated
- Rehabilitation approach (often focused on motion and function), if used as part of overall care planning
- Weight-bearing status, if modified as part of a broader management plan (details vary by clinician and case)
- Comorbidities and overall health, which can affect tolerance of treatment pathways
A given Herring classification grade is often recorded at a specific timepoint, but clinicians may update their assessment as imaging becomes clearer or as the hip changes through the natural stages of Perthes disease.
Alternatives / comparisons
Herring classification is one tool among several. Alternatives are not “better” in all cases; they answer different questions or apply at different timepoints.
Herring classification vs observation/monitoring
- Observation/monitoring is a management strategy, not a classification.
- Herring classification can support monitoring decisions by describing severity on X-ray, but it does not replace clinical follow-up.
Herring classification vs other Perthes classification systems
- Catterall and Salter–Thompson are also used to describe severity, often emphasizing different imaging features or stages.
- Herring classification is frequently favored for its practical focus on lateral pillar height, but selection varies by clinician and case.
Herring classification vs MRI-based assessment
- MRI can show early changes (including soft tissue and marrow signals) that may not be visible on X-ray.
- X-ray-based Herring classification is more accessible and commonly used for serial comparisons, while MRI may be used when the diagnosis is uncertain or when more detail is needed (varies by clinician and case).
Herring classification vs outcome-focused grading
- Systems like Stulberg classification are often discussed later because they describe the healed shape and long-term joint congruence rather than early severity.
- Herring classification is generally used earlier to support prognosis and planning.
Herring classification Common questions (FAQ)
Q: What condition is Herring classification used for?
It is primarily used for Legg–Calvé–Perthes disease in children. The classification describes how much the outer part of the femoral head has maintained its height on X-ray. It is not typically used for adult hip arthritis or other pediatric hip diagnoses.
Q: Does the Herring classification grade explain why my child has hip or knee pain?
It helps describe the structural changes seen on imaging, which may correlate with symptoms, but pain is influenced by multiple factors. Muscle tightness, inflammation, gait changes, and activity levels can all affect discomfort. Symptom severity does not always match X-ray severity.
Q: Is Herring classification the same as a “stage” of Perthes disease?
Not exactly. “Stage” usually refers to the phase of disease evolution over time (for example, when fragmentation is present). Herring classification is a severity grading based on the lateral pillar appearance on X-ray, often applied during a stage when those changes can be assessed.
Q: Can the Herring classification change over time?
The recorded grade reflects what is visible on a specific X-ray at a specific time. As the disease evolves and imaging becomes clearer, clinicians may re-assess severity, especially if earlier films were borderline or taken at a different phase. How often this happens varies by clinician and case.
Q: How does the grade affect treatment decisions?
Clinicians often use the grade as one piece of the overall picture, along with age, hip motion, walking pattern, and other imaging findings. In general terms, more preserved lateral pillar height suggests more favorable structural preservation, while more collapse suggests greater concern for shape changes. Exact decisions vary by clinician and case.
Q: Is it safe to get the X-rays needed for Herring classification?
Plain radiographs use ionizing radiation, but the amount is typically kept as low as reasonably achievable with pediatric protocols. Clinicians balance the need for diagnostic clarity and follow-up with minimizing exposure. Imaging choices depend on clinical context.
Q: How much does it cost to be evaluated with Herring classification?
The classification itself is part of interpreting imaging, so costs relate to clinic visits, radiographs, and sometimes advanced imaging. Out-of-pocket costs vary widely by region, insurance coverage, facility type, and billing structure. A clinic or hospital billing office is usually the best source for estimates.
Q: Does the grade tell how long recovery will take?
Not precisely. Perthes disease typically unfolds over a prolonged period, and timelines vary by child and by severity. The grade can help frame expectations about structural involvement, but it cannot provide an exact timeline for symptom improvement or return to activities.
Q: Will my child need to stop sports or change weight-bearing based on the grade?
Activity recommendations are part of a broader care plan and are not dictated by the classification alone. Clinicians consider pain, hip motion, gait, and imaging trends, and recommendations can change over time. Specific restrictions, if any, vary by clinician and case.
Q: If the grade is “worse,” does that automatically mean surgery is needed?
No. The classification does not mandate a single treatment pathway. It helps estimate severity and risk, but management decisions also depend on age, clinical findings, and how the hip is moving and functioning. Treatment approaches vary by clinician and case.