Differential Diagnosis for SLE Patient with Right Knee Pain and Limited Hip Movement

• Single Most Likely Diagnosis
  • B. Avascular necrosis of hip joint: This is a common complication in patients with Systemic Lupus Erythematosus (SLE), especially those on long-term corticosteroid therapy. The patient's complaint of right knee pain with limited movement of the right hip, particularly on internal rotation, is suggestive of hip joint pathology. Avascular necrosis (AVN) can cause such symptoms and is a well-known association with SLE and steroid use.
• Other Likely Diagnoses
  • C. Degenerative changes of hip joint: While less specific to SLE, degenerative changes can occur in any patient and might be exacerbated by the inflammatory nature of SLE. However, the patient's age and the presence of SLE might make AVN a more likely consideration.
• Do Not Miss Diagnoses
  • A. Septic infection of hip joint: Although the patient's symptoms and the normal imaging of the left knee and pelvis might not strongly suggest septic arthritis, it is a critical diagnosis not to miss due to its potential for severe and rapid joint destruction. SLE patients are at increased risk of infections, making this a crucial consideration.
• Rare Diagnoses
  • Other rare diagnoses might include conditions such as Slipped Capital Femoral Epiphysis (SCFE) in younger patients or Transient Osteoporosis of the Hip, but these would be less likely given the context of SLE and the specific symptoms described.

It's essential to note that the imaging provided was of the left knee and pelvis, which were normal, but the symptoms were on the right side, suggesting that targeted imaging of the right hip would be necessary to confirm the diagnosis.