title: The John Insall Award: control-matched evaluation of painful patellar Crepitus after total knee arthroplasty.
abstract: BACKGROUND
  Patellar crepitus (PC) is reported in up to 14% of subjects implanted with cruciate-substituting total knee arthroplasty (TKA). Numerous etiologies of PC have been proposed.
  
  
  OBJECTIVE
  We determined when painful PC typically occurs postoperatively and compared patients undergoing primary TKA who developed painful PC requiring subsequent surgery with a matched group without this complication to identify clinical, radiographic, and surgical variables associated with this complication.
  
  
  METHODS
  From the databases of two institutions (greater than 4000 TKAs), we identified 60 patients who required surgery for painful PC from 2002 to 2008. This group was then compared with an identified control group of 60 TKA subjects without PC who were matched for the key variables of age, gender, and body mass index to determine clinical, radiographic, and surgical factors associated with the development of PC.
  
  
  RESULTS
  The mean time to presentation of PC was 10.9 months. The incidence of PC correlated with a greater number of previous knee surgeries, decreased patellar component size, decreased composite patellar thickness, shorter preoperative and postoperative patellar tendon length, increased posterior femoral condylar offset, use of smaller femoral components and thicker tibial polyethylene inserts, and placement of the femoral component in a flexed posture.
  
  
  CONCLUSIONS
  Many of the factors associated with an increased incidence of postoperative PC such as shortened patellar tendon length, use of smaller patellar components, decreased patellar composite thickness, and increased posterior femoral condylar offset may all increase quadriceps tendon contact forces against the superior aspect of the intercondylar box, increasing the risk of fibrosynovial proliferation and entrapment within the intercondylar region of the femoral component. Based on these findings, the authors recommend use of larger patellar components when possible, avoid oversection of the patella or increasing posterior femoral condylar offset, and advising patients preoperatively who have had previous knee surgery or demonstrate a shortened patellar tendon length of an increased risk of development of postoperative patellar crepitus.
  
  
  METHODS
  Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
authors: Colorado Joint Replacement, 2535 S Downing Street, #100, Denver, CO 80210, USA. kslutzky@coloradojoint.com
authors: Douglas A
authors: DA
authors: Dennis
authors: Raymond H
authors: RH
authors: Kim
authors: Derek R
authors: DR
authors: Johnson
authors: Bryan D
authors: BD
authors: Springer
authors: Thomas K
authors: TK
authors: Fehring
authors: Adrija
authors: A
authors: Sharma
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000295:instrumentation; D001363:Awards and Prizes; D016022:Case-Control Studies; D003120:Colorado; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009657:North Carolina; D016017:Odds Ratio; D010147:Pain Measurement; D010149:Postoperative Pain / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery; D010329:Patella / Q000000981:diagnostic imaging / Q000601:surgery*; D011474:Prosthesis Design; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult