Understanding Anatomy and Associated Conditions

While the name Proximal Femoral Focal Deficiency (PFFD) focuses on the hip and thigh, it is important to understand that this is often a “global” condition. This means it can affect the entire leg, from the hip down to the toes ^[1][2].

Understanding the anatomy helps you move from seeing a “short leg” to understanding the specific structures that your medical team will need to monitor and treat.

PFFD vs. DDH: More Than a Dislocation

You may hear people mention Developmental Dysplasia of the Hip (DDH), a much more common condition where the “ball” of the hip is simply out of its socket. It is critical to know that PFFD and DDH are very different:

• DDH (The Fit): In DDH, the bones themselves are usually normal in shape and length, but they aren’t positioned correctly in the joint.
• PFFD (The Bone): In PFFD, the bone itself is structurally different (hypoplasia). The thigh bone (femur) is not just out of place; it is shorter, shaped differently, and the marrow cavity inside the bone is often narrower than normal ^[3][4].

The “Hidden” Knee: Why MRI is Mandatory

Even if your child’s knee looks normal on the outside, the internal structures are often missing or underdeveloped. This is known as ligamentous agenesis ^[5].

• Missing Ligaments: Many children with PFFD are born without an ACL (Anterior Cruciate Ligament) or PCL (Posterior Cruciate Ligament), which are the “straps” that keep the knee stable ^[6][7].
• Why it matters: If a surgeon tries to lengthen a leg without knowing the knee is unstable, the knee joint could dislocate during the process. An MRI is essential to map out these ligaments before any surgical planning begins ^[5].

Fibular Hemimelia: The Most Common Partner

More than 50% of children with PFFD also have a condition called Fibular Hemimelia ^[8].

• Fibular Hemimelia means the smaller bone in the lower leg (the fibula) is either shorter than normal or completely missing.
• Impact on the Foot: When the fibula is affected, the ankle and foot are often involved too. You might notice a “ball-and-socket” ankle (which is less stable than a typical ankle) or fewer than five toes on the foot ^[1][1].

Summary of Commonly Affected Areas

Because PFFD is a global limb deficiency, your care team should be looking at the following areas:

Empowering Your Observations

As a parent, you are the most consistent observer of your child’s body. When you speak with your orthopedic surgeon, ensure they are evaluating the entire limb. A diagnosis of PFFD should always trigger a close look at the knee and the lower leg to ensure no part of the “global” deficiency is missed ^[5][8].