title: Is There a Threshold for Stiffness Complaints Following TKA on the WOMAC Stiffness Subscale?
abstract: BACKGROUND
  Stiffness complaints after total knee arthroplasty (TKA) are frequent, yet poorly understood and can be challenging for surgeons to address. The WOMAC stiffness subscale is a widely used measure of stiffness and can serve as a simple screening tool for complaints.
  
  
  OBJECTIVE
  We aimed to identify a threshold for stiffness complaints on the WOMAC stiffness subscale and investigate its overlap with range of motion (ROM) in TKA patients.
  
  
  METHODS
  TKA patients were enrolled preoperatively and followed for 6 months. At follow-up, patients reported their ROM, completed the WOMAC stiffness subscale (range 1-8 with 8 continuous stiffness) and indicated whether they experienced more stiffness than expected. To identify a threshold for complaints, we compared patients' WOMAC stiffness scores to when they experienced more stiffness than expected, visually, and statistically. We also mapped ROM limitations at 6 months to WOMAC stiffness scores. Finally, we determined if baseline characteristics were associated with stiffness complaints.
  
  
  RESULTS
  Two hundred and forty-six TKA patients were enrolled preoperatively with 82% follow-up rate at 6 months. Our results showed that patients with a WOMAC stiffness score = 3+ were significantly more likely to experience more stiffness than expected. Patients reporting full ROM (54%) reported a wide range of WOMAC stiffness subscale scores (1-6). Baseline WOMAC pain and function scores were the only factors associated with stiffness complaints.
  
  
  CONCLUSIONS
  ROM is a poor surrogate of patient-reported stiffness, and the patients' perception of "stiffness" is clearly more complex than just ROM. We identified a WOMAC threshold that could potentially easily serve this purpose.
authors.affiliation: Department of Healthcare Policy and Research, Weill Cornell Medical College, 425 East 61st Street, Third Floor, Suite 301, New York, NY 10065 USA ; Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Hassan M K
authors.initials: HM
authors.lastname: Ghomrawi
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Mancuso
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gonzalez Della Valle
authors.affiliation: New York University School of Medicine, New York, NY USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Herrero
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Geoffrey H
authors.initials: GH
authors.lastname: Westrich
keywords: WOMAC; stiffness; total knee arthroplasty