title: Synovial haemangioma of the knee: an under recognised condition.
abstract: BACKGROUND
  Synovial haemangioma is a rare type of tumour for which only around 200 cases have been reported worldwide. It usually occurs in the female population during the second decade of life and most commonly affects the knee joint. Patients can complain of pain, recurrent knee swelling and limitation of motion. Since these lesions are uncommon and radilogical findings are nonspecific, physician awareness is low and diagnosis is often delayed, leading in turn to treatment delays and irreversible complications of the affected joint.
  
  
  METHODS
  We report four cases of synovial haemangioma of the knee seen over a period of 20 years (1993-2013). Age at presentation ranged from six to 43 years (mean of 22.7 years) with an equal male-to-female ratio. Average duration of symptoms prior to treatment was three years--patients were often misdiagnosed and appropriate treatment was subsequently delayed. Radiographs showed moderate to severe degenerative changes. Magnetic resonance (MR) imaging revealed poorly defined intra-articular contrast-enhancing lesions, all of which were of the localised type. Three patients underwent open synovectomy and en bloc excision of the lesion; the fourth deferred surgery but continues to be monitored. Follow-up ranged from one to 11 years; all four patients are doing well, with no signs of symptom recurrence or progression.
  
  
  CONCLUSIONS
  Synovial haemangioma is a rare but treatable condition. It should remain a differential for any patient with recurrent knee-joint symptoms.
authors.affiliation: Musculoskeletal Tumour Service, Department of Orthopaedics, University of the Philippines-Philippine General Hospital, Ermita, Manila, Philippines. claire.lopezoliva@yahoo.com.
authors.forename: Clarissa Linda Liboro
authors.initials: CL
authors.lastname: Lopez-Oliva
authors.affiliation: Musculoskeletal Tumour Service, Department of Orthopaedics, University of the Philippines-Philippine General Hospital, Ermita, Manila, Philippines. ehwang@up.edu.ph.
authors.forename: Edward H M
authors.initials: EH
authors.lastname: Wang
authors.affiliation: Department of Radiology, University of the Philippines-Philippine General Hospital, Ermita, Manila, Philippines.
authors.forename: Johanna Patricia A
authors.initials: JP
authors.lastname: Cañal
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D057210:Delayed Diagnosis; D003951:Diagnostic Errors; D018450:Disease Progression; D005260:Female; D006391:Hemangioma / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis* / Q000601:surgery; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D013583:Synovial Membrane / Q000473:pathology*
keywords: Knee mass; Knee pain; Knee swelling; Synovial haemangioma