title: Case report: multifocal subchondral stress fractures of the femoral heads and tibial condyles in a young military recruit.
abstract: BACKGROUND
  Subchondral stress fractures of the femoral head may be either of the insufficiency-type with poor quality bone or the fatigue-type with normal quality bone but subject to high repetitive stresses. Unlike osteonecrosis, multiple site involvement rarely has been reported for subchondral stress fractures. We describe a case of multifocal subchondral stress fractures involving femoral heads and medial tibial condyles bilaterally within 2 weeks.
  
  
  METHODS
  A 27-year-old military recruit began having left knee pain after 2 weeks of basic training, without any injury. Subsequently, right knee, right hip, and left hip pain developed sequentially within 2 weeks. The diagnosis of multifocal subchondral stress fracture was confirmed by plain radiographs and MR images. Nonoperative treatment of the subchondral stress fractures of both medial tibial condyles and the left uncollapsed femoral head resulted in resolution of symptoms. The collapsed right femoral head was treated with a fibular strut allograft to restore congruity and healed without further collapse.
  
  
  METHODS
  There has been one case report in which an insufficiency-type subchondral stress fracture of the femoral head and medial femoral condyle occurred within a 2-year interval.
  
  
  CONCLUSIONS
  Because the incidence of bilateral subchondral stress fractures of the femoral head is low and multifocal involvement has not been reported, multifocal subchondral stress fractures can be confused with multifocal osteonecrosis. Our case shows that subchondral stress fractures can occur in multiple sites almost simultaneously.
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Korea.
authors.forename: Pil Whan
authors.initials: PW
authors.lastname: Yoon
authors.forename: Jeong Joon
authors.initials: JJ
authors.lastname: Yoo
authors.forename: Kang Sup
authors.initials: KS
authors.lastname: Yoon
authors.forename: Hee Joong
authors.initials: HJ
authors.lastname: Kim
mesh_terms: D000328:Adult; D015519:Bone Density; D005270:Femur Head / Q000000981:diagnostic imaging / Q000293:injuries*; D005360:Fibula / Q000637:transplantation; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000628:therapy*; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000601:surgery / Q000628:therapy*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008889:Military Personnel; D011859:Radiography; D013978:Tibial Fractures / Q000000981:diagnostic imaging / Q000628:therapy*; D014184:Transplantation, Homologous