🧬 biology

Genetic susceptibility to anterior cruciate ligament rupture in athletes: a genome-wide association case–control study

This genome-wide association study of 607 athletes of European ancestry failed to identify genome-wide significant genetic variants for anterior cruciate ligament rupture but highlighted several suggestive loci involved in inflammation, cellular stress, and ciliary function that warrant further investigation in larger cohorts.

Original authors: Miklós Tátrai, András Tállay, Tamás Halasi, Eszter Papp, András Pavlik, Csaba Barta, Ábel Fóthi, Zsolt Rónai, Hajnalka Vágó, Attila Pavlik

Published 2026-06-30

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Original authors: Miklós Tátrai, András Tállay, Tamás Halasi, Eszter Papp, András Pavlik, Csaba Barta, Ábel Fóthi, Zsolt Rónai, Hajnalka Vágó, Attila Pavlik

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine your body's ligaments, like the Anterior Cruciate Ligament (ACL) in your knee, are the strong ropes holding a tent together. Sometimes, even with good weather and careful setup, a rope snaps. For a long time, doctors and scientists have wondered: "Why does this rope snap for some athletes but not others?"

We know that bad luck (like landing awkwardly) and external factors (like a slippery field) play a part. But this study asked a different question: Is there a hidden "instruction manual" inside our DNA that makes some people's ropes more likely to snap than others?

Here is the story of what the researchers found, explained simply.

The Big Search (The "Genome-Wide" Hunt)

The researchers gathered a team of 607 people of European descent.

The "Snapped Rope" Group: 401 athletes who had their ACLs tear (some tore one knee, some tore both).
The "Strong Rope" Group: 206 active athletes who had never injured their ACL, no matter how hard they played.

They didn't just look at a few specific genes they guessed might be important. Instead, they did a "genome-wide" search. Think of this like reading every single page of a massive 3-billion-word instruction book (your DNA) to find any tiny typos that might be different between the two groups.

The Results: No "Smoking Gun," But Some "Faint Clues"

The most important thing to know is this: They did not find a single, definitive genetic "smoking gun."

In the world of genetics, a "smoking gun" is a specific genetic typo so obvious that it proves it causes the injury. This study didn't find any that were strong enough to be called a fact.

However, they did find some faint clues. Imagine you are looking for a needle in a haystack. They didn't find the needle, but they did find a few pieces of thread that looked suspiciously like they might belong to a needle. These were genetic variations that showed up more often in the injured group, but not often enough to be 100% sure.

The "Suspicious" Characters

The study highlighted several specific genes that showed these faint clues. The researchers compared them to characters in a story, noting what they usually do in the body:

The Firefighters (ITGAM, GALNT11): These genes are usually involved in how the body handles inflammation and immune responses. The researchers suspect that maybe, in some people, the body's way of reacting to tiny, invisible micro-tears in the ligament isn't quite right, making the rope weaker over time.
The Stress Managers (HSPA12A, NEK10): These genes help cells deal with stress and repair themselves. If these managers are a bit "off," maybe the ligament can't bounce back from the daily wear and tear of sports.
The Tiny Builders (C10orf82, NEK10): Some of these genes are involved in building tiny hair-like structures called "cilia" on cells. This was a surprise! The researchers had no idea these tiny builders had anything to do with knee ligaments. It's like finding out that the quality of a tent's rope depends on the design of the tent's tiny ventilation tubes.
The Pain/Signal Switches (OPRD1, OR7E47P): Some clues pointed to genes that usually handle pain signals or smell (even though one was a "broken" smell gene). This suggests the injury might be linked to how the body senses or signals pain and stress.

What Does This Mean?

The authors are very careful not to overpromise. They say:

We don't have a test yet: You cannot take a DNA test today and know if you will tear your ACL.
It's a "Hypothesis Generator": Think of this study as a map that points to a few interesting islands. It doesn't tell us what's on the islands yet, but it tells us where to look next.
The "Super-Strong" Control Group: A unique part of this study was that the "healthy" group wasn't just random people off the street; they were active athletes who had never hurt their knees. This makes the comparison very strict.

The Bottom Line

The researchers concluded that while there is no single "ACL gene" that guarantees an injury, there are likely many tiny genetic factors working together. These factors seem to be related to how the body handles inflammation, stress, and cellular repair.

They found some interesting suspects (like the genes mentioned above), but they need to check these clues with a much larger group of people in the future before they can say, "Yes, this is definitely why some athletes get hurt."

In short: The study didn't find the "magic bullet" gene, but it did find a few interesting footprints that suggest the story of ACL injuries is more complex and involves more parts of the body's instruction manual than we previously thought.

Technical Summary: Genetic Susceptibility to Anterior Cruciate Ligament Rupture in Athletes

Problem Statement
Anterior cruciate ligament (ACL) rupture is a prevalent and severe injury among athletes, often resulting in prolonged rehabilitation and delayed return to sport. While the injury mechanism typically involves non-contact valgus trauma, risk is modulated by a complex interplay of external factors (e.g., surface conditions) and internal factors (e.g., neuromuscular control, anatomy, and genetics). Previous genetic investigations have largely relied on candidate gene approaches focusing on collagen structure (e.g., COL3A1), extracellular matrix (ECM) remodeling, and inflammatory mediators. However, these studies have yielded inconsistent results, and robust, genome-wide significant associations remain elusive. Furthermore, existing literature often lacks rigorous phenotypic characterization of controls, frequently utilizing unscreened general populations rather than active athletes without injury history. This study addresses the gap in hypothesis-free, genome-wide analysis of genetic susceptibility to ACL rupture within a well-characterized athletic cohort.

Methodology
This study employed a case–control design conducted between 2019 and 2024 in Hungary. The cohort consisted of 607 participants of European ancestry:

Cases: 401 patients with confirmed ACL rupture, subdivided into unilateral (ACL1, n=293) and bilateral (ACL2, n=108) groups. Diagnosis was confirmed via arthroscopic evaluation, MRI, and surgical reports.
Controls: 206 screened active athletes (aged ≥19) with no history of ACL injury.

Genotyping and Analysis:

Data Collection: DNA was extracted from buccal epithelial cells.
Platform: Genotyping was performed using the Illumina Global Screening Array (GSA) MD v3.0.
Quality Control (QC): Rigorous QC was applied using PLINK v1.9. Criteria included call rates >98%, removal of individuals with sex discrepancies or excess heterozygosity, exclusion of cryptic relatedness (PI_HAT > 0.2), and filtering for minor allele frequency (MAF) >1% and Hardy–Weinberg equilibrium.
Population Stratification: Multidimensional scaling (MDS) was performed using pruned SNPs against the 1000 Genomes Project reference panel to ensure only individuals clustering with the European (EUR) group were retained.
Statistical Modeling: Association analyses utilized logistic regression under an additive genetic model, adjusting for the top 10 MDS components.
Significance Thresholds: The study applied a genome-wide significance threshold of $p < 5 \times 10^{-8}$ and a suggestive significance threshold of $p < 5 \times 10^{-5}$ to identify candidate loci.

Key Results

Demographics: No significant differences were found in sex distribution across groups. However, the unilateral ACL group (ACL1) was significantly younger than controls, and both ACL groups had significantly lower Tegner activity scores compared to controls.
Genome-Wide Significance: No variants reached the genome-wide significance threshold ( $p < 5 \times 10^{-8}$ ).
Suggestive Associations: Several loci demonstrated suggestive associations ( $p < 5 \times 10^{-5}$ $p < 5 \times 1 0^{- 5}$ ) across different comparison groups:
- ACL vs. Controls: The strongest signals were observed in or near GALNT11 (5 SNPs, lowest $p = 2.46 \times 10^{-5}$ ), ITGAM (3 SNPs), C10orf82, and OR7E47P.
- Unilateral (ACL1) vs. Controls: Suggestive associations were found in HSPA12A and OR7E47P.
- Bilateral (ACL2) vs. Controls: A cluster of 4 SNPs was identified in the OPRD1 gene.
- Unilateral vs. Bilateral (ACL1 vs. ACL2): Enrichment of 4 SNPs was observed around the NEK10 gene.

Key Contributions and Claims
The primary contribution of this work is the execution of a hypothesis-free genome-wide association study (GWAS) in a highly specific cohort: active athletes with verified injury status compared against a "super-negative" control group of active athletes without injury history. This design minimizes the phenotypic heterogeneity often found in previous studies.

The authors identify several novel genetic candidates that have not been traditionally implicated in ligament biology:

Inflammatory and Immune Regulation: ITGAM (integrin alpha M) is linked to leukocyte adhesion and inflammatory responses, suggesting a potential role in tissue remodeling following micro-injury.
Cellular Stress and Signaling: HSPA12A (a heat shock protein) and NEK10 (a kinase involved in DNA damage response and ciliogenesis) point toward mechanisms involving cellular stress adaptation and metabolic regulation.
Ciliary Function and Glycosylation: GALNT11, C10orf82, and NEK10 are associated with ciliary structure, function, or O-glycosylation pathways, introducing a previously unexplored biological dimension to ligament integrity.
Pain Perception: OPRD1 (delta opioid receptor) suggests a potential, albeit speculative, link to pain modulation or injury susceptibility mechanisms.

Significance and Limitations
The paper modestly frames its findings as "hypothesis-generating." The authors explicitly state that no definitive genetic markers for ACL susceptibility were established, as no variants reached genome-wide significance. The significance of the study lies in highlighting biological pathways—specifically inflammation, cellular stress responses, and ciliary function—that warrant further investigation.

The authors acknowledge several limitations:

Sample Size: While larger than many candidate gene studies, the cohort (n=607) may lack the statistical power required to detect variants with small effect sizes at genome-wide significance.
Population Specificity: The exclusive focus on Hungarian/European ancestry limits the generalizability of findings to other ethnic groups.
Design Constraints: The cross-sectional nature prevents causal inference, and environmental/biomechanical factors were not comprehensively assessed.
Functional Validation: The biological relevance of the identified loci remains unproven and requires functional validation.

In conclusion, the study suggests that genetic susceptibility to ACL rupture may extend beyond traditional collagen-related genes to include regulatory genes involved in inflammation and cellular stress, but firm conclusions require replication in larger, independent cohorts.