Gravity-Assisted Passive Flexion in Total Knee Arthroplasty Recovery

Orthopedics. 2020 Sep 1;43(5):e431-e437. doi: 10.3928/01477447-20200721-09. Epub 2020 Aug 6.


This study examined the use of gravity-assisted passive flexion (GAP-FLEX) for perioperative total knee arthroplasty (TKA) recovery. The main questions associated with this technique were: (1) Can GAP-FLEX improve patient recovery of range of motion after TKA? (2) Does GAP-FLEX reduce patient time and effort associated with therapy compared with continuous passive motion (CPM)? (3) Does GAP-FLEX reduce overall episodic care cost? A prospective, randomized multicenter study was conducted. Two senior surgeons used identical surgical approach, prosthesis, and postoperative management protocols. Patients consenting to the study were randomly assigned to either standard of care (CPM) or GAP-FLEX groups. Active flexion range of motion (ROM) was measured via goniometer with a primary endpoint established at 4 weeks after surgery. Secondary endpoints included pain and functional mobility. A total of 27 patients completed the study. Average ROM in the GAP-FLEX sample was 8.4° greater than the CPM sample (P=.009) at study endpoint. The GAP-FLEX patients achieved greater postoperative ROM within 2 days and maintained an improvement over CPM to study endpoint. Eighty-five percent (11 of 13) of GAP-FLEX patients achieved or surpassed their baseline ROM by study endpoint, compared with 50% (7 of 14) of CPM patients. These improvements occurred while requiring 90% less therapy time on device compared with the CPM patients. Patients did not report any statistically different pain levels but did exhibit higher functional mobility at endpoint (P=.026). [Orthopedics. 2020;43(5):e431-e437.].

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Arthroplasty, Replacement, Knee / rehabilitation*
  • Female
  • Gravitation
  • Humans
  • Male
  • Middle Aged
  • Motion Therapy, Continuous Passive / methods*
  • Postoperative Period
  • Prospective Studies
  • Range of Motion, Articular*
  • Treatment Outcome