Trochanteric Bursitis: This condition is characterized by inflammation of the bursa over the greater trochanter, leading to pain on the lateral aspect of the hip. The pain is often exacerbated by activities that involve adduction of the hip, such as crossing the legs or standing with the affected leg adducted. The location and nature of the pain, along with worsening symptoms upon adduction, make trochanteric bursitis a highly plausible diagnosis.

Gluteus Medius Tendinopathy: Similar to trochanteric bursitis, gluteus medius tendinopathy affects the lateral hip and can cause pain that worsens with activities involving hip adduction. This condition involves inflammation or degeneration of the gluteus medius tendon and is a common cause of lateral hip pain.
Iliotibial (IT) Band Syndrome: Although more commonly associated with knee pain, IT band syndrome can also cause hip pain, especially in the lateral aspect. The pain can be exacerbated by activities that involve repetitive hip adduction, such as cycling or running.
Piriformis Syndrome: This condition involves the piriformis muscle compressing the sciatic nerve, leading to pain in the buttock and hip area. While the primary complaint is often buttock pain, some patients may experience anterior and lateral hip pain, especially if the piriformis muscle is tight and contributes to altered hip mechanics.

Avascular Necrosis (AVN) of the Femoral Head: Although less common, AVN is a critical diagnosis not to miss due to its potential for severe and irreversible damage to the hip joint. Early stages may present with hip pain that worsens with weight-bearing activities, including those that involve adduction.
Stress Fracture: Stress fractures around the hip can cause significant pain, especially with weight-bearing activities. While they might not always present with pain specifically worsened by adduction, they are a critical diagnosis to consider due to the risk of fracture displacement and long-term consequences.
Septic Arthritis: This is an infection within the joint space, which is a medical emergency. Patients may present with acute onset of hip pain, swelling, and decreased range of motion. While the pain pattern may not specifically worsen with adduction, the severity and acute onset of symptoms should prompt urgent evaluation.

Osteoid Osteoma: A benign bone tumor that can cause nocturnal pain and is often relieved by NSAIDs. The pain can be localized to any bone, including those around the hip, and might not have a specific relationship with hip adduction.
Synovial Chondromatosis: A rare condition characterized by the growth of cartilage in the synovial membrane of the joint, leading to joint pain and swelling. The symptoms can be non-specific and might include pain with various movements, including adduction.