This is the first study to show that there is a specific genetic risk factor associated with risk of anterior cruciate ligament ruptures in female athletes.

The TT genotype of the COL1A1 Sp1 binding site polymorphism was significantly under-represented in South African participants with ACL ruptures. We propose that this sequence variant be the first specific genetic element to be included in multifactorial models developed to understand the aetiology and risk factors for ACL rupture.

The COL12A1 AluI RFLP is associated with ACL ruptures among female participants in this study. The results suggest that females with an AA genotype are at increased risk of ACL ruptures. These initial genetic association studies should be explored further and, if repeated, incorporated into multifactorial models developed to identify predisposed individuals.

Angiogenesis-associated signaling is a fundamental component in the remodeling of the extracellular matrix in response to loading. Genes encoding protein components within this signaling cascade are therefore suitable candidates for investigation into ACL injury susceptibility: namely, vascular endothelial growth factor A isoform (VEGFA), kinase insert-domain receptor (KDR), nerve growth factor (NGF), and hypoxia inducible factor-1a (HIF1A). A case-control genetic association study was conducted on 227 asymptomatic control participants and 227 participants with surgically diagnosed ACL ruptures of which 126 participants reported a non-contact mechanism of rupture. All participants were genotyped for seven polymorphisms within the four genes. The VEGFA rs699947 CC genotype (p ¼ 0.010, OR: 1.92, 95% CI: 1.17-3.17) was significantly over-represented within participants with non-contact ACL ruptures. The VEGFA rs1570360 GA genotype was significantly over-represented in the CON group (p ¼ 0.007, OR: 1.70, 95% CI: 1.16-2.50). Furthermore, the KDR rs2071559 GA genotype was significantly over-represented in the female controls (p ¼ 0.023, OR: 2.16, 95% CI: 1.11-4.22). Inferred haplotype analyses also implicated genomic regions spanning the VEGFA and KDR genes. These novel findings suggest that regions within VEGFA and KDR may be implicated in the pathophysiology of ACL ruptures; highlighting the potential biological significance of angiogenesis-associated signaling in the aetiology of ACL ruptures. ß

The COL5A1 and COL12A1 variants are independently associated with modulating the risk of anterior cruciate ligament (ACL) rupture in females. The objective of this study was to further investigate if COL3A1 and COL6A1 variants independently, as well as, collagen gene-gene interactions, modulate ACL rupture risk. Three hundred and thirty-three South African (SA, n = 242) and Polish (PL, n = 91) participants with diagnosed ACL ruptures and 378 controls (235 SA and 143 PL) were recruited. Participants were genotyped for COL3A1 rs1800255 G/A, COL5A1 rs12722 (T/C), COL6A1 rs35796750 (T/C) and COL12A1 rs970547 (A/G). No significant associations were identified between COL6A1 rs35796750 and COL3A1 rs1800255 genotypes and risk of ACL rupture in the SA cohort. The COL3A1 AA genotype was, however, significantly (p = 0.036) over-represented in the PL ACL group (9.9%, n = 9) when compared to the PL control (CON) group (2.8%, n = 4). Although there were genotype distribution differences between the SA and PL cohorts, the T+A-inferred pseudo-haplotype constructed from COL5A1 and COL12A1 was significantly over-represented in the female ACL group when compared to the female CON group within the SA (T+A ACL 50.5%, T+A CON 38.1%, p = 0.022), PL (T+A ACL 56.3%, T+A CON 36.3%, p = 0.029) and combined (T+A ACL 51.8%, T+A CON 37.5%, p = 0.004) cohorts. In conclusion, the novel main finding of this study was a significant interaction between the COL5A1 rs12722 T/C and COL12A1 rs970547 A/G variants and risk of ACL injury. These results highlight the importance of investigating gene-gene interactions in the aetiology of ACL ruptures in multiple independent cohorts.