Congenital femoral deficiency means the thigh bone is short or partly missing from birth. We explain how it is diagnosed, why classification matters and how staged reconstruction is planned.
On this page 8 sections
- What is congenital femoral deficiency and what causes it?
- How is congenital femoral deficiency diagnosed?
- Does the leg length difference grow with the child?
- How does classification shape the treatment plan?
- What are the reconstruction options for congenital femoral deficiency?
- What should families expect during treatment?
- When should you see a doctor?
- Key points
Congenital femoral deficiency is a rare condition in which the thigh bone (femur) is short, misshapen or partly missing from birth. In mild forms the femur is simply shorter than the other side; in more severe forms the hip joint, the upper end of the femur and the knee are also affected. Treatment is planned individually after examination and imaging, guided by the leg length difference expected at the end of growth, how stable the hip and knee are, and what the family hopes to achieve.
The condition used to be called proximal femoral focal deficiency (PFFD). The broader term congenital femoral deficiency (CFD) is now preferred because it covers the whole spectrum, from a slightly short femur to a major deficiency. Published estimates vary, but it is generally reported in roughly 1 in 50,000 to 1 in 200,000 births, and it usually affects one leg only.
What is congenital femoral deficiency and what causes it?
The femur takes shape in the first weeks of pregnancy. A disturbance in the way the thigh bone grows and forms during this window leaves the bone short and changes the structures around the hip and knee. In most children no specific cause is found. CFD is usually not inherited, and it is not caused by anything the parents did or did not do during pregnancy.
CFD is more than a short bone. Commonly associated findings include:
- Hip: a reduced femoral neck angle (coxa vara), a shallow hip socket (acetabular dysplasia) and tight soft tissues that hold the hip bent and turned outwards.
- Knee: underdeveloped or absent cruciate ligaments with a resulting looseness of the knee, a kneecap that tends to slip outwards, and a tendency towards knock knee (valgus).
- Lower leg and foot: underdevelopment of the fibula, the thin bone beside the shin bone, on the same side (fibular hemimelia), with related ankle and foot deformities.
How is congenital femoral deficiency diagnosed?
For many families the first suspicion arises at the detailed mid-pregnancy anomaly scan, when one femur measures shorter than the other. This finding is valuable for counselling and for planning assessment after birth, but the definitive diagnosis and classification are made once the baby is born.
After birth, parents or midwives may notice a short, bulky thigh, a hip that rests bent and turned outwards, or asymmetric skin creases. The main tools used in assessment are:
- Clinical examination: range of movement at the hip and knee, stability of the knee ligaments and the shape of the foot.
- X-rays: the length and shape of the femur and how far it has ossified (turned from cartilage into bone).
- MRI: in babies the top of the femur is still cartilage and may be invisible on X-ray. MRI shows whether a cartilaginous femoral head and neck are present, which helps with classification.
- Standing full-length leg X-rays: once the child can stand, these films measure the length difference and any alignment problems.
Does the leg length difference grow with the child?
In CFD the affected femur usually grows at a constant, slower rate than the femur on the healthy side. The difference in centimetres therefore increases as the child grows, while the proportion between the two legs stays roughly the same. This allows the difference at skeletal maturity to be predicted from measurements taken in early childhood. Methods such as Paley's multiplier method are used for this, and predictions are refined with repeated measurements. Our article on leg length discrepancy in children explains how these measurements work in general.
How does classification shape the treatment plan?
The most widely known historical system is the Aitken classification (types A to D), based on the appearance of the femoral head and hip socket on X-ray. The Paley classification, widely used for reconstruction planning, focuses instead on whether the hip and knee move and where the femur is deficient, so it points more directly to treatment options.
| Paley type | Main feature | General direction of treatment |
|---|---|---|
| Type 1 | Intact femur with mobile hip and knee; ossification of the upper femur normal or delayed | Hip and knee preparatory surgery if needed, then lengthening |
| Type 2 | Mobile false joint in the upper femur; femoral head mobile in the socket, or absent or fused to it | Reconstruction of the hip, followed by staged lengthening |
| Type 3 | Deficiency of the femoral shaft; knee movement preserved or very limited | Lengthening or prosthesis-oriented options discussed with the family |
| Type 4 | Deficiency of the lower femur | Individual reconstruction plan |
A classification is not a label; it is a shared language for the team and the family. Even within the same type, the hip, knee and foot findings can differ from one child to another.
What are the reconstruction options for congenital femoral deficiency?
The goals of treatment are to balance leg lengths as far as possible by the end of growth, to keep the hip and knee stable and mobile, to give the child a well-aligned foot to stand on, and to allow an active life at school, at play and in sport. Options generally fall into the following groups.
Non-surgical measures
For small differences, or in the periods between surgical stages, shoe raises or orthoses may be used. They do not lengthen the bone, but they help to balance walking and reduce strain on the hips and spine.
Preparatory surgery
If the hip or knee is unstable, the joints need to be made secure before any lengthening. The procedures described by Dror Paley, known as "SUPERhip" and "SUPERknee", aim to correct the hip angle and socket, release tight soft-tissue bands and, where necessary, reconstruct deficient knee ligaments. This preparation is intended to reduce the risk of the hip or knee dislocating during later lengthening.
Bone lengthening
Lengthening relies on a controlled cut in the bone that is then gradually distracted, usually at around 1 mm a day, so that new bone forms in the gap. In CFD the total difference often cannot be corrected in a single lengthening, and two or more stages spaced several years apart may be planned through childhood. In young children external fixators (Ilizarov-type circular frames or monolateral systems) are most often used, and the frame may be extended across the knee to the shin bone to protect the joint. Once the bone is large enough, internal lengthening nails may also be considered. You can read more about the principles on our medical limb lengthening page.
Guided growth
In suitable patients with a relatively small predicted difference, slowing or stopping growth at the growth plate of the healthy leg at the right age (epiphysiodesis) may be planned on its own or combined with lengthening.
Prosthesis-oriented options
Where the deficiency is very severe and knee function is limited, procedures that make a prosthesis easier to use, such as rotationplasty, in which the ankle is turned to work as a knee, are discussed in detail with the family. These are equally valid, function-focused paths; the decision brings together the child's needs and the family's values.
What should families expect during treatment?
Treatment for CFD is usually a roadmap that spans years. Lengthening phases call for frequent reviews, regular physiotherapy and careful frame care. Problems such as joint stiffness, a tendency for the hip or knee to sublux (partly dislocate), slow hardening of the new bone or a fracture of the new bone can occur, which is why the process is followed closely by an experienced team. The child's schooling, emotional support and the family's daily routine are part of the plan too. The timing of each stage depends on the individual.
When should you see a doctor?
It is worth seeing a doctor experienced in paediatric orthopaedics if:
- a pregnancy scan has shown one femur measuring shorter than the other
- your baby's thigh looks clearly short or bulky, or the hip constantly rests bent and turned outwards
- your child limps once walking begins, or walks on tiptoe on the shorter side
- the knee gives way, feels unstable or the kneecap slips out of place
- the difference in leg length seems to become more obvious over time
Prof. Dr. Halil İbrahim Balcı worked at the Paley Institute in the United States as a research fellow in 2014 and as an observer in 2019, focusing on congenital bone anomalies and limb lengthening. Related conditions are covered on our rare childhood limb deformities page.
Key points
- Congenital femoral deficiency means the thigh bone is short or partly missing from birth; it usually affects one leg.
- Associated hip, knee and foot problems shape the treatment plan as much as the length difference itself.
- Because the difference stays proportionally constant, the length difference at maturity can be predicted early.
- Options include orthoses, preparatory surgery, staged lengthening, epiphysiodesis and prosthesis-oriented procedures.
- The right path is agreed with the family after examination and imaging; results vary from child to child.
Frequently Asked Questions
In most children congenital femoral deficiency occurs sporadically and is not inherited, so the chance of it happening again in a later pregnancy is generally considered low. The situation can differ in some rare syndromes where the femoral deficiency comes with other congenital differences. If such a syndrome is suspected, the child is assessed together with a clinical geneticist, and the family receives advice specific to their own circumstances.
There is no single correct age. If the hip or knee is unstable, preparatory surgery is usually planned in early childhood, once the bone and soft tissues are large enough. The first lengthening often follows this preparation. Timing depends on the child's age, the classification type, the condition of the hip and knee and the predicted length difference, and it is discussed in detail with the family before any decision is made.
This depends on the length difference expected at the end of growth and on how much lengthening the joints can safely tolerate at each stage. In mild forms a single lengthening or an epiphysiodesis may be enough, whereas larger differences may call for two or more stages spaced years apart during childhood. The plan is updated over time according to the child's growth and how they responded to earlier stages.
Most children with this condition learn to walk, sometimes with a shoe raise, an orthosis or a prosthesis at first. The quality of walking and the level of sport they can enjoy depend on the severity of the deficiency, the condition of the hip and knee and the treatment chosen. Regular physiotherapy, maintaining joint movement and steady family support all help children stay active alongside their peers.
No. When both femurs measure short, the cause may be family build, the baby's overall growth pattern or other conditions affecting skeletal development. A clear difference between the two sides is more suggestive of congenital femoral deficiency. Follow-up scans, and examination and imaging after birth, are what clarify the picture, so firm conclusions should not be drawn from a single measurement.
This article is for general information only and does not replace a medical examination, diagnosis or treatment. Treatment options and outcomes vary from person to person.
Related treatment area Rare Childhood Limb Deformities: Fibular Hemimelia, Femoral Deficiency
