What condition is suspected in a 50-year-old woman experiencing left hip pain with marked tenderness over the proximal lateral thigh?

Trochanteric bursitis, often referred to as greater trochanteric pain syndrome, is characterized by tenderness over the lateral aspect of the hip, particularly around the greater trochanter. This condition typically arises from inflammation of the bursa that lies between the greater trochanter of the femur and the overlying iliotibial band. In individuals around the age of 50, such as the woman described in the question, this condition is quite common due to factors like overuse, repetitive movements, or even biomechanical issues.

The marked tenderness over the proximal lateral thigh suggests that the inflammation is localized, a characteristic feature of trochanteric bursitis. The pain may also be exacerbated by certain activities or positions, such as lying on the affected side or climbing stairs, which aligns with a typical presentation of this condition. The age of the patient and the specific location of pain and tenderness support the diagnosis of trochanteric bursitis as the most likely underlying issue in this scenario.

While the other conditions listed could be associated with hip pain, they typically present with different symptoms and locations of tenderness. Osteoarthritis, for instance, tends to cause a more generalized stiffness and pain in the hip joint rather than localized tenderness.