You Keep Tearing Your Labrum Because Your Cartilage Was Built From a Weaker Blueprint

Type V collagen is the quality-control protein of connective tissue. It does not make up the bulk of a tendon or labrum, but it controls how the much larger type I collagen fibers assemble, setting their diameter and spacing. Get this regulation right and you get dense, well-organized fibers that resist tearing.

The T allele at rs12722 changes how this regulator works, producing fibers that are organized differently and less able to handle repetitive and rotational load. **This variant is carried by roughly 30 to 35 percent of people and is one of the most consistently replicated genetic markers for tendon and ligament injury in athletes.** It is especially relevant in runners and any sport built on repetitive motion.

Day to day, this is the athlete who tears, rehabs diligently, returns, and tears again in the same region. The tissue is being asked to do its job with a blueprint that produces a weaker weave, so the recurrent labrum fraying is not bad luck, it is structural.

Type I collagen is the dominant structural protein in your labrum, tendons, ligaments, and bone. It is the rope that bears the load. The body manufactures it in a precise ratio of protein chains, and that ratio determines how much tension the tissue can take before it fails.

The Sp1 variant rs1800012 shifts that production ratio and changes the makeup of the type I collagen the body builds. **The T allele is carried by roughly 25 to 30 percent of people and is associated with cruciate ligament rupture, shoulder dislocation, and tendon injury across impact and contact sports.** The altered ratio produces a rope that is wound slightly wrong.

For you, this can show up as a shoulder that dislocates or subluxes more easily and a labrum that gives way under loads other athletes shrug off. The tissue is not lazy, it was simply assembled from a recipe that trades a little tensile strength away.

Growth differentiation factor 5 is the signal that tells your body how to build and maintain joints, cartilage, and the tendons that anchor them. It drives the development of healthy connective tissue and keeps the repair machinery responsive when that tissue gets stressed.

The rs143383 risk allele lowers GDF5 expression in connective tissue, and it is common: **the risk allele is carried by roughly 40 to 60 percent of people, and lower GDF5 signaling is linked to osteoarthritis, Achilles tendinopathy, and patellar (jumper’s) knee.** Less of this growth signal means joints that develop and repair with less structural reserve.

In practice this is the athlete whose joints feel a step behind in recovery, where cartilage and the labral rim wear faster than the training load alone would explain. The catch, the ache, and the slow return after each setback can trace back to a connective-tissue system running on a quieter build signal.

Matrix metalloproteinase 3 is the demolition-and-rebuild enzyme of connective tissue. After every microtear, it clears away damaged matrix so new collagen can be laid down. Healthy remodeling is a balance: enough breakdown to clear debris, enough restraint to let new tissue mature.

The rs679620 variant tips that balance and alters extracellular-matrix turnover and tendon healing. **This variant is carried by roughly 40 percent of people and is associated with Achilles tendinopathy and recurrent soft-tissue injury in athletes.** When the remodeling rhythm is off, the new tissue laid down after a tear can be lower quality and slower to fully mature.

This is why your labrum can feel healed and then fail again under the first real test. The repair crew is doing the work, but the rebuild is not as durable, so the same region keeps reopening.

Tenascin-C is a matrix protein that helps organize the connective-tissue scaffold and guides cells during loading and repair. It shapes how the tendon and labral matrix is composed, influencing how the tissue distributes mechanical stress.

The rs2104772 and variable-number-repeat variants change tendon matrix composition, and prevalence varies by ancestry. **These variants alter the structural makeup of the tendon matrix and are associated with higher Achilles tendon injury risk**, a marker for how the broader connective-tissue scaffold is built. A differently composed matrix can concentrate stress where it is least able to handle it.

For you, this can mean tissue that frays at predictable weak points and a recovery that lags after each loading cycle. The scaffold holding your labrum together was assembled with a slightly different recipe, so it absorbs load differently than the bodies of athletes who rarely tear.

The vitamin D receptor is how your cells actually read and use vitamin D, which is required for muscle protein synthesis, calcium signaling, and the recovery that protects the joints muscles are meant to stabilize. When this receptor works well, your tissue translates vitamin D into real repair and adaptation.

The BsmI and FokI variants change how efficiently the receptor functions, and **these variants are carried by roughly 30 to 50 percent of people and can impair recovery and training adaptation even when blood vitamin D looks normal.** A blood test can show adequate vitamin D while your cells still struggle to use it.

This often looks like an athlete who supplements vitamin D, sees normal labs, and still recovers slowly and adapts poorly, leaving the stabilizing muscles around the shoulder underpowered. When those muscles cannot protect the joint, more load lands directly on the labrum.