Postpartum Pelvic Girdle Pain: This condition is common during and after pregnancy due to hormonal changes and mechanical stress on the pelvic girdle. The symptoms of intermittent dull to moderate pain, worsened by movement such as bending or standing for long periods, are consistent with this diagnosis. The onset in the third trimester and persistence postpartum further support this likelihood.

Osteitis Pubis: Inflammation of the pubic bone and its surrounding structures, which can occur postpartum due to the stress of childbirth on the pelvic area. Symptoms include pain in the pubic area that can radiate to the hips and worsen with movement.
Sacroiliac Joint Dysfunction: The sacroiliac joints can become inflamed or dysfunctional during pregnancy due to the increased mobility caused by hormonal changes. This can lead to hip and lower back pain that worsens with activities like bending or standing.
Stress Fracture: Although less common, stress fractures in the hip or pelvis can occur, especially if there was increased activity during pregnancy or postpartum. Pain typically worsens with weight-bearing activities.

Osteonecrosis of the Femoral Head: A condition where the blood supply to the femoral head is interrupted, leading to bone death. It can be a complication of pregnancy due to increased coagulability and potential for thrombosis. Early diagnosis is crucial for treatment to prevent collapse of the femoral head.
Deep Vein Thrombosis (DVT): Although DVT typically presents with leg swelling and pain, in some cases, it can cause hip pain if the clot is located in the pelvic veins. Given the increased risk of thromboembolism postpartum, it's essential to consider DVT in the differential diagnosis.
Septic Arthritis: Infection within a joint, which can occur postpartum, especially if there were any complications during delivery. It presents with severe pain, swelling, and decreased range of motion of the affected joint.

Pregnancy-Associated Osteoporosis: A rare condition where pregnancy leads to a significant loss of bone density, potentially resulting in fractures. Hip pain could be a symptom if there's a fracture or significant bone loss in the hip area.
Primary Bone Tumors: Although extremely rare, primary bone tumors (benign or malignant) could present with hip pain. The pain is typically constant and worsens at night, but any new onset of hip pain warrants a thorough investigation.