The morbidity associated with idiopathic osteonecrosis of the femoral head (ION) is increasing. The primary goal of treatment for ION is to prevent collapse of the femoral head. With the exception of hip arthroplasties, current joint-preserving surgeries for ION require long-term reduction of the load placed on the hip joint. To allow these patients to return quickly to their daily and social activities, we have developed a novel extra-articular device that reduces the weight-bearing of the hip joint. In this study, we evaluated the load-bearing function and the range of motion of a hip joint equipped with the extra-articular device. To demonstrate load reduction on the hip joint with this device, we measured the contact pressure on the femoral head surface and the principal strain on the coxal bone during static loading conditions, which simulated the various phases of human gait. The range of motion of the hip joint with the device was measured using an electro-goniometer. The extra-articular device remarkably reduced the contact pressure on the hip joint, with some restriction in hip flexion. Our novel extra-articular device appears to be a promising tool to secure reductions in the weight-bearing function of the hip joint, and will be applicable to new bone regeneration therapies.