Developmental Dysplasia

Developmental dysplasia of the hip — DDH — is the umbrella term for a hip socket that didn't form quite right. The socket (the cup that the ball at the top of the thigh bone fits into) is too shallow, tilted too vertical, or otherwise shaped so it doesn't fully cover the ball. The hip is mechanically less stable, the labrum and cartilage take abnormal stress every step you walk, and arthritis tends to set in years earlier than in a normal hip.

DDH ranges from a subtle under-cup that only shows up on imaging in your 20s, all the way to a hip that's already dislocated at birth. Mild cases often go undetected for decades — patients first show up with hip or groin pain, a torn labrum, or early arthritis in their 20s, 30s, or 40s. Women are affected more often than men.

Many young adults with mild DDH have no idea anything is wrong until groin pain starts — typically a deep ache in the front of the hip that comes on with walking, stair climbing, or sitting for a long time. The pain often builds gradually over months. Clicking, catching, or a sharp pinch with certain hip positions points to a labral tear, which is common because the shallow socket forces the labrum to carry loads it wasn't designed for.

You may notice that your hip feels stiff after sitting and loosens up after a few minutes of walking. Some patients feel a sense of instability — as though the hip is about to give way — especially during single-leg activities like lunging or pivoting. A limp may develop as symptoms progress, and one leg may feel shorter than the other if the socket coverage is significantly asymmetric.

Young adults with dysplasia usually show up with groin pain and signs of a labral tear. The key measurement is the lateral center-edge angle taken from a standing pelvis X-ray — anything under about 25° means the socket isn't covering the ball enough. MRI shows the labrum and cartilage; CT gives a full 3D model of the bony anatomy when surgery is being planned.

1. Intra-articular injection

   An injection of numbing medication and corticosteroid directly into the hip joint — both diagnostic (if it relieves the pain, the joint is the source) and therapeutic (calms labral-driven pain).

Surgery is considered when symptoms are significant and the anatomy can still be corrected. The goal of joint-preserving surgery (a periacetabular osteotomy) is to physically rotate the socket into better position so it covers the ball properly — done before the cartilage takes irreversible damage. For hips that are already arthritic, hip replacement is the answer.

External patient-education references and related OSI pages for additional background:

• Britannica — Hip (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language