Differential Diagnosis for Right Anterior Hip Pain with Restricted Hip Extension

• Single most likely diagnosis
  • Psoas major: The psoas major muscle is a key flexor of the hip, and its tightness or spasm can restrict hip extension. Given the patient's presentation of right anterior hip pain and restricted hip extension, the psoas major is the most likely muscle responsible for this limitation.
• Other Likely diagnoses
  • Piriformis: Although the piriformis muscle primarily affects external rotation of the hip, it can also contribute to restrictions in hip movement, including extension, especially if it is tight or inflamed.
  • Adductor magnus: While the adductor magnus is more involved in hip adduction, its proximal attachment and role in hip stability mean it could potentially contribute to restrictions in hip extension, especially if there is significant tightness or pathology.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pathology involving the lumbar spine (e.g., disc herniation, spinal stenosis): Although not directly a muscle issue, conditions affecting the lumbar spine can refer pain to the hip and restrict movement. Missing a serious spinal condition could have significant consequences.
  • Intra-abdominal or pelvic pathology (e.g., appendicitis, diverticulitis): Certain intra-abdominal conditions can cause hip pain due to referred pain patterns and should be considered to avoid missing a potentially life-threatening condition.
• Rare diagnoses
  • Quadratus lumborum: While the quadratus lumborum can contribute to lower back and pelvic stability, it is less commonly associated directly with restrictions in hip extension compared to other muscles listed.
  • Biceps femoris: The biceps femoris, part of the hamstring group, is more involved in knee flexion and hip extension rather than restriction of hip extension. Its involvement would be less likely given the presentation.