What you carry at this position in your DNA and what research says about it.
Bone Density and Injury Risk: 4/10 evidence, 28 publications.
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Sample genotype (not yours): C/C
Typical Bone Density and Injury Risk
Standard collagen production supports typical bone mineral density and normal skeletal strength. Risk levels for osteoporosis, fractures, and joint injuries remain at the population baseline.
What this genotype means: Typical bone mineral density; Standard baseline risk of fractures; Standard baseline risk of ACL tears.
Sample genotype (not yours): A/A
Higher Bone Loss Risk but Lower ACL Rupture Risk
Two copies of the variant allele significantly increase the risk of bone loss and disc disease, but offer notable protection against ACL ligament tears.
What this genotype means: Increased risk of osteoporosis and bone fractures; Significantly lower risk of ACL ligament ruptures; Higher susceptibility to intervertebral disc degeneration.
Sample genotype (not yours): C/A
Slightly Higher Risk of Bone Loss
A single copy of the variant allele is associated with a mild reduction in bone mineral density. This can slightly elevate the long-term risk of osteoporosis and bone fragility.
What this genotype means: Slightly lower bone mineral density; Slightly increased risk of osteoporosis; Potential for reduced bone density when taking certain medications.
Gene function and biological role
Gene Function: The COL1A1 gene encodes the major component of type I collagen, which is the primary structural protein found in bones, skin, tendons, and other connective tissues [1]. Type I collagen fibers provide essential tensile strength and structural integrity throughout the musculoskeletal system [2]. Variations in this gene can alter the ratio of collagen chains produced, directly affecting how tightly these fibers are woven [3]. Consequently, these molecular changes can influence bone mineral density, susceptibility to fractures, and the elasticity of ligaments [4].
Variant Impact: The rs1800012 variant is located in the first intron of the COL1A1 gene and alters a binding site for the Sp1 transcription factor [1]. This nucleotide change increases transcription factor binding, which leads to an overproduction of the collagen alpha-1 chain relative to the alpha-2 chain [3]. The resulting imbalance causes the assembly of weaker collagen homotrimers instead of the normal, stronger heterotrimers [5]. This structural alteration compromises the strength of bone tissue while paradoxically altering the mechanical properties of ligaments [6].
Key Insight: An imbalance in collagen chain production can weaken bone density but simultaneously make ligaments more pliable, reducing the likelihood of sudden joint tears.
Location: COL1A1. Chromosome 17 · 17q21.33 · 50.2 Mb
Estimated prevalence by population
Global 74.8%; European 66.3%; African 86.3%; East Asian 99.5%; South Asian 83.0%; Americas 73.3%; Ashkenazi 66.8%; Finnish 75.0%; Middle Eastern 67.2%; Amish 74.4%.
Estimated CC genotype frequency.
Global 23.0%; European 30.3%; African 13.2%; East Asian 0.5%; South Asian 16.2%; Americas 24.7%; Ashkenazi 29.8%; Finnish 23.2%; Middle Eastern 29.6%; Amish 23.7%.
Estimated CA genotype frequency.
Global 2.2%; European 3.5%; African 0.5%; East Asian < 0.1%; South Asian 0.8%; Americas 2.1%; Ashkenazi 3.3%; Finnish 1.8%; Middle Eastern 3.3%; Amish 1.9%.
Estimated AA genotype frequency.
Showing effects for C/C genotype
Organ Systems
Bone, Joint & Connective Tissue Health
Bone Mineral Density. Evidence: 4/10. Source: PMID 8841196. Typical Density.
Osteoporosis. Evidence: 4/10. Source: PMID 9535665. Typical Risk.
Spinal Disc Disease. Evidence: 3/10. Source: PMID 29088884. Typical Risk.
Lifestyle, Fitness & Aging
Injury Risk & Recovery
ACL Rupture Risk. Evidence: 3/10. Source: PMID 19193663. Typical Risk.
Showing effects for A/A genotype
Bone Mineral Density. Evidence: 4/10. Source: PMID 8841196. Decreased Density.
Osteoporosis. Evidence: 4/10. Source: PMID 9535665. Higher Risk.
Spinal Disc Disease. Evidence: 3/10. Source: PMID 29088884. Higher Risk.
ACL Rupture Risk. Evidence: 3/10. Source: PMID 19193663. Lower Risk.
Showing effects for C/A genotype
Bone Mineral Density. Evidence: 4/10. Source: PMID 8841196. Slightly Decreased.
Osteoporosis. Evidence: 4/10. Source: PMID 9535665. Slightly Higher Risk.
Spinal Disc Disease. Evidence: 3/10. Source: PMID 29088884. Slightly Higher Risk.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Standard structural integrity of type I collagen fibers is maintained by this genotype, which represents the most common genetic profile globally. Normal transcription factor binding ensures a balanced ratio of collagen chains, supporting optimal bone mineralization [1]. Clinical studies consistently associate this profile with typical bone mineral density and a standard baseline risk for osteoporosis and low-energy fractures [2]. While bone health is well-supported, the natural stiffness of standard collagen fibers means there is no additional genetic protection against ligament injuries like ACL tears [3]. Maintaining a balanced diet rich in calcium and engaging in regular weight-bearing exercise helps preserve this natural skeletal strength over time.
Typical bone mineral density; Standard baseline risk of fractures; Standard baseline risk of ACL tears.
Sample genotype: AA (Homozygous)
An altered ratio of collagen chains leads to the formation of weaker collagen homotrimers, which compromises the structural strength of bones [1]. This significant structural change is strongly linked to reduced bone mineral density, accelerated bone loss, and a higher risk of osteoporosis and fractures [2]. The structural weakness also extends to the spine, increasing susceptibility to intervertebral disc degeneration [3]. However, this same structural flexibility in collagen fibers appears to make ligaments more elastic and resilient to sudden mechanical stress [4]. As a result, this genotype is highly protective against anterior cruciate ligament (ACL) ruptures [4]. Individuals may also show a poorer response to certain bone-building therapies like etidronic acid [5].
Increased risk of osteoporosis and bone fractures; Significantly lower risk of ACL ligament ruptures; Higher susceptibility to intervertebral disc degeneration.
Sample genotype: CA (Heterozygous)
Slightly altered collagen fiber composition occurs due to a minor imbalance in the production of collagen alpha-1 chains [1]. This subtle structural shift can lead to a modest reduction in bone mineral density, particularly in postmenopausal women [2]. While the impact is generally mild, individuals with this genotype may experience a slightly elevated risk of developing osteoporosis or experiencing fractures over their lifetime [3]. Additionally, certain medications like valproic acid may further compound bone density loss in carriers of this variant [4]. Standard joint and ligament strength remain close to typical baseline levels. Prioritizing bone-supporting lifestyle habits, such as adequate vitamin D intake and resistance training, can help mitigate these minor risks.
Slightly lower bone mineral density; Slightly increased risk of osteoporosis; Potential for reduced bone density when taking certain medications.
Variants with shared genetic architecture
rs11898505 · SPTBN1 Gene · Chr 2 · Bone Density
rs3736228 · LRP5 Gene · Chr 11 · Bone Density and Fractures
rs6426749 · ZBTB40 Gene · Chr 1 · Bone Mineral Density
Genetic risk factors for anterior cruciate ligament ruptures: COL1A1 gene variant.
Content updated August 2026.
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