title: Which factors predict the long-term outcome in chronic patellofemoral pain syndrome? A 7-yr prospective follow-up study.
abstract: OBJECTIVE
  The aim of this prospective study was to determine which factors predict the long-term (7-yr) outcome of conservative treatment of chronic patellofemoral pain syndrome.
  
  
  METHODS
  The general predictors registered were age, gender, body composition, athletic activity, duration of symptoms, and follow-up time. The remaining 13 predictors were clinical or radiological measurements of the knee joint. In 45 consecutive patients, these predictors were measured at the beginning of the 6-wk treatment protocol (rest, NSAID, and intense isometric quadriceps exercises) and at the end of the follow-up. The outcome criteria were the 100-mm Visual Analog Scale (VAS) pain score, and the Lysholm and Tegner functional knee scores.
  
  
  RESULTS
  The extension strength of the affected knee was a significant predictor of the outcome scores (Lysholm score: r = 0.37, P < 0.05, and the Tegner score: r = 0.39, P < 0.01): the smaller the strength difference between the affected and unaffected knee, the better the outcome. In a multiple stepwise regression analysis, the variables pain in the patella apprehension test, patella crepitation at baseline and at follow-up, bilateral symptoms developed during the follow-up, and patient's age and height were also independent predictors of the final outcome and could together account 60% for the variation seen in the Lysholm score and 52% in the Tegner score, respectively. Neither the radiologic nor the magnetic resonance imaging changes at the affected knee had a clear association with the 7-yr outcome.
  
  
  CONCLUSIONS
  The results of the current and our previous (15) observations support the concept that restoration of good quadriceps strength and function to the affected extremity is important for good recovery of the patient. In addition, negative findings in the clinical tests of patellar pain and crepitation, nonappearance of bilateral symptoms during the follow-up, low body height, and young age are associated with good long-term outcome.
authors.affiliation: Tampere Research Center of Sports Medicine and Accident and Trauma Research Center, UKK Institute, Finland. jnatri@zoo.uvm.edu
authors.forename: A
authors.initials: A
authors.lastname: Natri
authors.forename: P
authors.initials: P
authors.lastname: Kannus
authors.forename: M
authors.initials: M
authors.lastname: Järvinen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D018771:Arthralgia / Q000534:rehabilitation / Q000628:therapy*; D001823:Body Composition / Q000502:physiology; D001827:Body Height; D002908:Chronic Disease; D005081:Exercise Therapy; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010329:Patella / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011446:Prospective Studies; D011859:Radiography; D012044:Regression Analysis; D012146:Rest; D012737:Sex Factors; D013177:Sports / Q000502:physiology; D013577:Syndrome; D016896:Treatment Outcome
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal