Differential Diagnosis for Pain in Left Hip on Flexion and Internal Rotation

Single Most Likely Diagnosis

• Femoroacetabular Impingement (FAI): This condition is characterized by abnormal contact between the femoral head and the acetabulum, leading to pain, especially with flexion and internal rotation of the hip. The mechanism of injury and the specific movements that exacerbate the pain align closely with the symptoms of FAI.

Other Likely Diagnoses

• Labral Tear: Tears in the labrum, the cartilage that surrounds the socket of the hip joint, can cause pain with movements that involve flexion and internal rotation. This is because such movements can irritate or further injure the labrum.
• Piriformis Syndrome: This condition involves the piriformis muscle compressing or irritating the sciatic nerve, leading to pain in the hip and buttock area. While it more commonly presents with pain radiating down the leg, it can also cause localized hip pain, especially with certain movements.
• Osteoarthritis: Hip osteoarthritis can cause pain with various movements, including flexion and internal rotation, due to the degeneration of the joint cartilage and the resultant bone-on-bone contact.

Do Not Miss Diagnoses

• Septic Arthritis: Although less common, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. It can present with acute onset of hip pain, especially with movement, and is accompanied by systemic symptoms such as fever.
• Avascular Necrosis (AVN): AVN of the femoral head can cause hip pain that worsens with weight-bearing and certain movements. It is crucial to diagnose AVN early to prevent further damage to the hip joint.
• Slipped Capital Femoral Epiphysis (SCFE): In adolescents, SCFE is a condition where the ball at the upper end of the femur (thigh bone) slips out of place. It can cause hip pain that worsens with movement and is a critical diagnosis to make promptly to avoid long-term damage.

Rare Diagnoses

• Synovial Chondromatosis: A rare condition characterized by the growth of cartilage in the synovium of the joint, leading to pain and mechanical symptoms.
• Intra-articular Tumors: Tumors within the hip joint, such as chondroblastoma or synovial sarcoma, are rare but can cause pain and stiffness, especially with movement.
• Legg-Calve-Perthes Disease: A rare childhood hip disorder initiated by a disruption of blood flow to the ball of the femur called the femoral head, leading to pain and limited mobility.