1. BIOCHEMICAL MARKERS OF TYPE II COLLAGEN DEGRADATION AND SYNTHESIS ARE NOT ASSOCIATED WITH BIOMECHANICAL VARIABLES IN PATIENTS FOLLOWING ACL RECONSTRUCTION Solis FM 1, Trumble TN 2, Leeuwenburgh C 1, Shuster J 1, Dominguez JA1 1, Cicuttini FM 3, Chmielewski TL 1 1 University of Florida, Gainesville, Florida, USA. 2 University of Minnesota, St. Paul, Minnesota, USA. 3 Monash University, Melbourne, Australia BIOCHEMICAL MARKERS OF TYPE II COLLAGEN DEGRADATION AND SYNTHESIS ARE NOT ASSOCIATED WITH BIOMECHANICAL VARIABLES IN PATIENTS FOLLOWING ACL RECONSTRUCTION Solis FM 1, Trumble TN 2, Leeuwenburgh C 1, Shuster J 1, Dominguez JA1 1, Cicuttini FM 3, Chmielewski TL 1 1 University of Florida, Gainesville, Florida, USA. 2 University of Minnesota, St. Paul, Minnesota, USA. 3 Monash University, Melbourne, Australia BACKGROUND Post-traumatic knee osteoarthritis (OA) is prevalent after anterior cruciate ligament reconstruction (ACLR). OA results in part from an imbalance in type II collagen metabolism with a shift towards greater degradation than synthesis. Serum C-propeptide of type II collagen (sCPII), a biomarker of type II collagen synthesis, and urinary CTX-II (uCTXII) a biomarker of type II collagen degradation can be used to monitor articular cartilage metabolism. While articular cartilage responds to mechanical loading in vitro, it is unknown if jump-landing forces influence biomarker levels. In addition, it is unknown if quadriceps strength protects articular cartilage when jump-landing activities are initiated. OBJECTIVES METHODS STATISTICAL ANALYSIS Pearson’s correlation, with and without adjustment for age, was used to analyze associations of sCPII, uCTX-II, and uCTX-II/sCPII with PVGRF and PKET. RESULTS Table: Mean values for biomarkers and biomechanical variables on the surgical side Figure 2: correlation between PKET and uCTX-II:sCPII was r = 0.406, p =.076 There were no significant correlations between biomarkers of synthesis and degradation with PVGRF on the surgical side (p ≥ 0.2), except for a trend towards a positive correlation between PKET and uCTXII:sCPII. CONCLUSIONS In a population of young individuals with ACLR, biomarkers of type II collagen metabolism were not associated with jump-landing forces. However, higher quadriceps strength may be associated with a shift in articular cartilage metabolism towards degradation. CLINICAL RELEVANCE Jump-landing forces may not provide insight into articular cartilage status until patients have increased the frequency of jump-landing tasks. Higher quadriceps strength is usually a goal in ACLR rehabilitation, but its potential role in articular cartilage degradation needs to be examined further. 22 patients with ACLR Male = 14, Age = 19.6 ± 4 yr Subjects were tested after the 8 week of low- or high-intensity plyometric exercise. Early morning blood and urine samples were collected. sCPII and uCTX-II were analyze using commercial ELISAs. uCTX-II was corrected for creatinine concentrations using another ELISA method Biomarker concentrations were log transformed prior to statistical analysis. Subjects performed 3 trials of a forward drop land and a drop vertical jump. Subjects started on a 20 cm step and landed on a force platform (AMTI). Peak vertical ground reaction forces (PVGRF) from forward drop land and drop vertical jump were analyzed on the surgical side and averaged across trials. Quadriceps strength (peak knee extensor torque, PKET) was assessed with an isokinetic dynamometer (60°/s). PVGRF and PKET were normalized to body weight (BW). To investigate the association of sCPII, uCTX-II, and uCTX-II:sCPII with PVGRF and quadriceps strength in patients with ACLR. VariablesMean ± SD sCPII (lpg/µmol )2.88 ± 0.19 uCTX-II (pg/µmol )3.32 ± 0.49 uCTX-II:sCPII1.16 ± 0.18 PVGRF (BW) Forward drop land 3.2 ± 0.3 PVGRF (BW) Drop vertical jump 1.4 ± 0.3 PKET (BW)0.92 ± 0.2 AKNOWLEDGMENT NFL Charities NIH-NICHD K01-HD052713