Osteochondral injury increases type II collagen degradation products (C2C) in synovial fluid of Thoroughbred racehorses

SummaryObjectivesTo investigate the effects of exercise and osteochondral (OC) injury on type II collagen degradation products (collagenase cleavage neoepitope commercially known as C2C) in synovial fluid (SF) from Thoroughbred (TB) racehorses and to compare these results with radiographic and arthroscopic scores of severity of joint injury.MethodsMetacarpophalangeal/metatarsophalangeal (MCP/MTP) and carpal SF was obtained from (1) 20 normal rested horses, (2) the same horses after 5 to 6 months of race training, and (3) 27 horses with OC injury from racing. For group 3, radiographic and arthroscopic scores were determined. Concentrations of SF C2C were determined by ELISA.ResultsSF C2C concentrations in OC injured carpal and MCP/MTP joints were significantly different than rested and exercised joints (P < 0.01). However, carpal and MCP/MTP SF C2C concentrations were not significantly different between rested and exercised groups. Arthroscopic scores were significantly higher for OC injured carpal than OC injured MCP/MTP joints (P = 0.002). OC injured SF C2C concentrations were positively correlated with radiographic and arthroscopic scores. Arthroscopic scores were positively correlated with radiographic scores. SF C2C concentrations ≥64 pmol/mL for MCP/MTP joints and ≥75 pmol/mL for carpal joints discriminated OC injured joints from rested or exercised joints.ConclusionOC injury caused a significant increase in SF C2C concentrations in carpal and MCP/MTP joints compared to rested and exercised horses. SF C2C concentrations were correlated to severity of joint injury. Based on these findings, SF C2C analysis may be useful for evaluation of joint injury.