title: Hyaluronic acid injections protect patellar tendon from detraining-associated damage.
abstract: BACKGROUND
  Having previously demonstrated that detraining affects patellar tendon (PT) proteoglycan content and collagen fiber organization, we undertook the present study with two aims: to improve knowledge on the adaptation of PT and its enthesis to detraining from a histological and histomorphometric point of view, and to investigate the hypothesis that repeated peri-patellar injections of hyaluronic acid (HA) on detrained PT may reduce and limit detrained associated-damage.
  
  
  METHODS
  Twenty-four male Sprague-Dawley rats were divided into 3 groups: Untrained (n=6), Trained (n=6) (10 wks-treadmill) and Detrained (n=12). In the detrained rats, the left tendon was untreated while the right tendon received repeated peri-patellar injections of either HA or saline (NaCl). Structure and morphology of PTs (modified Movin score, tear density, collagen type I and III) and enthesis (cell morphology, chondrocyte cluster formation, tidemark integrity, matrix staining and vascularization) were evaluated.
  
  
  RESULTS
  The left PT and enthesis of the Detrained groups showed altered structure and morphology with the highest Movin score values, the highest percentage of collagen III and the lowest of collagen I; the lowest score values were observed in the Trained and Detrained-HA groups. Detrained-NaCl PTs showed the highest collagen III and the lowest collagen I values with respect to Detrained-HA PTs.
  
  
  CONCLUSIONS
  This study strengthens previously published data showing the alteration in tendon and enthesis morphology due to discontinuation of training, and provides new data showing that treatment with HA is effective in the maintenance of the structural properties of PT and enthesis in Detrained rats. Such beneficial effects could play a significant role in the management of conservative and rehabilitation strategies in athletes that change type, intensity and duration of training.
authors.affiliation: Department of Orthopaedic Rehabilitation, University of Padova School of Medicine, Padova, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Frizziero
authors.affiliation: Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies-Department Rizzoli RIT- Rizzoli Orthopaedic Institute, Bologna, Italy. francesca.salamanna@ior.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Salamanna
authors.affiliation: Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies-Department Rizzoli RIT and Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Giavaresi
authors.affiliation: Department of Orthopaedic Rehabilitation, University of Padova School of Medicine, Padova, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ferrari
authors.affiliation: Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies-Department Rizzoli RIT and Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Martini
authors.affiliation: Department of Experimental, Diagnostic, and Specialty Medicine, University of Bologna, Bologna, and Center of Sports Medicine, Don Gnocchi Foundation, IRCCS, Milan, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Marini
authors.affiliation: Center of Sports Medicine, Don Gnocchi Foundation, IRCCS, and Department of Biomedical Sciences for Health, University of Milan, Milan, Italy.
authors.forename: Arsenio
authors.initials: A
authors.lastname: Veicsteinas
authors.affiliation: Department of Phisical and Rehabilitation Medicine, University of Salerno, San Giovanni Di Dio and Ruggi d'Aragona Hospital, Salerno, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Maffulli
authors.affiliation: Department of Orthopaedic Rehabilitation, University of Padova School of Medicine, Padova, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Masiero
authors.affiliation: Laboratory of Biocompatibility, Technological Innovations and Advanced Therapies-Department Rizzoli RIT and Laboratory of Preclinical and Surgical Studies, Rizzoli Orthopaedic Institute, Bologna, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Fini
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D006820:Hyaluronic Acid / Q000494:pharmacology*; D008297:Male; D017847:Patellar Ligament / Q000187:drug effects*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D055675:Viscosupplements / Q000494:pharmacology*
chemical_list: D055675:Viscosupplements; D006820:Hyaluronic Acid