Progesterone and Injury Risk: What the Hormonal Cycle Really Means for Female Athletes’ Ligaments
Table of Contents
Key Takeaways: Progesterone and Injury Risk
- Female athletes have higher ACL injury rates than male athletes, and menstrual-cycle hormones — including progesterone — may be one piece of this complex risk picture.
- Studies suggest that the progesterone-dominant luteal phase may be associated with a lower risk of ACL injury compared with other menstrual-cycle phases, but the relationship is not simple or fully understood.
- Progesterone may counterbalance some estrogen-related effects on ligament collagen biology, while other hormones such as relaxin may influence connective tissue in the opposite direction.
- Hormonal contraception and progestin-only formulations are scientifically interesting areas of research, but current evidence does not support using them specifically as an injury-prevention strategy.
- Menstrual-cycle tracking can provide useful context for symptoms, fatigue, and recovery, but there are currently no clear evidence-based rules for assigning specific types of training to specific cycle phases.
- For athletes, established injury-prevention strategies — including neuromuscular training, appropriate load management, recovery, and individualized monitoring — remain more actionable than trying to optimize performance or injury risk through hormone manipulation.
Introduction: Progesterone and Injury Risk
Female athletes suffer ACL tears at rates reported to be three to six times higher than male athletes [1], and for years the search for “why” has focused mostly on estrogen. Progesterone gets far less attention — yet research on progesterone and injury risk suggests it may be an important, underappreciated part of the explanation for why risk shifts across the menstrual cycle, and why the relationship is not as simple as “high hormones equal high risk.”
In clinical practice, progesterone is usually familiar to both clinicians and patients in a much narrower context. Most people associate it with contraception, progestin-only pills, hormonal intrauterine devices, menstrual regulation, or delaying menstrual bleeding. It is often viewed mainly as a reproductive hormone — something used to control or modify the menstrual cycle.
What many athletes may not realize is that progesterone also has biological roles beyond reproduction, including possible effects on connective tissue. Its relationship with ligament biology and injury risk is a fascinating example of how complex the human body can be.
At the same time, this needs to be interpreted carefully. In everyday clinical practice, progesterone and injury risk remain more of a physiological insight than a routine factor guiding medical decisions. Understanding progesterone’s role does not mean predicting injuries from hormone levels — but it can give athletes and coaches a more complete picture of why injury risk may fluctuate across the menstrual cycle.
Progesterone and Injury Risk: Why the Prevalence Data Matters
The idea that progesterone and injury risk are linked across the menstrual cycle isn’t new. In a case-control study of recreational alpine skiers, skiers whose menstrual cycle phase was staged using serum progesterone concentrations were significantly more likely to tear their ACL during the preovulatory phase (low progesterone) than the postovulatory phase (odds ratio 3.22, 95% CI 1.09-9.52, P = .027) [2]. Notably, when the same cohort was instead classified using self-reported menstrual history rather than hormone testing, the same direction of effect appeared but did not reach statistical significance (odds ratio 2.38, 95% CI 0.86-6.54, P = .086) [2] – a useful reminder that hormone-confirmed cycle staging and self-reported cycle staging don’t always agree, and that the strength of a progesterone-and-injury-risk finding often depends on how rigorously “cycle phase” was actually measured.
Looking across multiple menstrual-cycle studies together, a systematic review and meta-analysis concluded that the luteal phase – when progesterone is highest – came out as the phase least associated with ACL injury in most (four of five) of the individual studies reviewed, among women not using hormonal contraception [1]. A separate systematic review and meta-analysis pooling nine studies and 2,519 subjects quantified this further, finding a significantly decreased relative risk of ACL tear in the luteal phase compared with the follicular and ovulatory phases combined (RR 0.72, 95% CI 0.56-0.89) [3].
A natural follow-up question is whether progesterone-containing contraceptives show a similar pattern. This is a complicated question because synthetic progestins are not identical to the body’s own progesterone, and hormonal contraceptives also change the normal cycling of multiple hormones. Interestingly, newer observational data suggest that some progestin-only oral contraceptive users may have lower rates of ACL injuries requiring reconstruction [7]. However, this should be interpreted as another clue in the progesterone-and-ligament biology discussion — not as evidence that the mini-pill should be used as an injury-prevention strategy.
In real-world practice, however, this remains mostly a point of physiological interest rather than a major driver of training or medical decisions. In my experience, it is still relatively uncommon for athletes to structure training blocks very precisely around menstrual cycle phase. Some athletes may track symptoms and adjust load or recovery accordingly, but competition schedules are usually fixed, and athletes often cannot choose when an important event falls in relation to their cycle.
The same caution applies to contraception. Current evidence is not strong enough to use progestin-only contraception as an injury-risk intervention, and there are no established clinical pathways that treat contraceptive choice as an ACL prevention strategy. For now, the practical value of this information is mainly interpretive: it can help athletes and clinicians understand one possible piece of the hormonal injury-risk puzzle, without turning progesterone into a treatment target.
The Mechanism Behind Progesterone and Injury Risk
The ACL is not just a passive rope of collagen — it appears to be hormonally responsive tissue. Estrogen, progesterone, testosterone, and relaxin receptors have all been identified on the ACL [1]. In cell-culture studies, increasing estradiol concentrations were associated with a dose-dependent decrease in ACL fibroblast proliferation and type I procollagen synthesis, while increasing progesterone concentrations attenuated that effect [1]. Put another way, progesterone may partly counterbalance some estrogen-related effects on ACL collagen metabolism. This offers one plausible mechanistic explanation — not a proven causal pathway — for why the progesterone-dominant luteal phase has been associated with lower ACL injury rates in some studies.
Relaxin adds another layer to progesterone and injury risk. This ovarian and placental hormone contributes to laxity of the pubic symphysis in pregnancy and childbirth and has also been postulated to affect the ACL in nonpregnant women [4]. In a small prospective study of elite female Division I athletes, relaxin levels greater than 6.0 pg/mL were associated with more than a fourfold higher risk of ACL tear; using this cutoff, the test had 71% sensitivity and 88% negative predictive value [4]. This makes relaxin an important part of the hormonal injury-risk discussion, but its clinical utility as a screening tool still requires further investigation.
Mechanistically, this is fascinating — but it should not be overtranslated into clinical or performance claims. The current understanding of progesterone, relaxin, and ligament biology is not mature enough to justify hormone-based strategies for improving performance or reducing injury risk. In practice, an athlete’s status as an athlete is not, by itself, an indication for hormone treatment. Hormonal therapy should be based on a broader clinical assessment, symptoms, contraceptive needs, menstrual health, medical contraindications, and the patient’s goals — not on the assumption that manipulating progesterone or related hormones will improve ligament resilience or athletic performance.
The same caution applies to training design. Cycle tracking can be useful context for symptoms, recovery, and individual patterns, but there is still no clear, broadly accepted evidence-based rule for exactly what type of training should be done in each phase of the menstrual cycle. In practice, training decisions still need to be based on the athlete’s overall load, recovery, symptoms, injury history, goals, and competition schedule — not on a rigid hormone-phase template.
This distinction matters because mechanistic plausibility can easily sound more actionable than it really is. For now, the progesterone-and-relaxin story is best understood as a useful biological framework for interpreting injury-risk patterns, not as a treatment pathway, performance-enhancement tool, or strict cycle-based training formula.
Progesterone and Injury Risk Beyond the Knee
The picture isn’t purely reassuring when it comes to progesterone and injury risk more broadly. A 2025 prospective study following 59 elite adolescent female team athletes across a season found the luteal phase was significantly associated with a higher overall incidence of sports injuries – specifically joint/ligament injuries (P = .024) and muscle/tendon injuries (P = .040) – alongside significantly worse sleep quality and greater fatigue (P < .001) during the early and late luteal phases [6]. That looks contradictory to the ACL-specific findings above, but it likely isn’t measuring the same thing. One plausible interpretation is that the ACL data reflects a structural, ligament-specific effect of progesterone on collagen, while the adolescent injury data reflects the systemic effects of the luteal phase – fatigue, poorer sleep, and reduced recovery – that can raise injury risk across many tissue types regardless of what’s happening at the ligament level [6].
For a knee-specific ligament like the ACL, progesterone’s local collagen-supportive effect on injury risk may dominate. For overall injury burden across a training season, the luteal phase’s toll on sleep and fatigue may matter more to injury risk than local hormone-receptor biology [6]. Both can be true at once, and an athlete or coach who only tracks one side of the progesterone-and-injury-risk equation will get an incomplete picture.
From a practical clinical perspective, this is where I would be careful not to overstate what hormone tracking can currently do. The menstrual cycle involves multiple interacting hormones, connective-tissue effects, sleep, fatigue, symptoms, training load, recovery, and competition timing. That system is too complex to reliably “optimize” with simple hormone-phase rules.
In my view, this information is nice to know, but it should mostly remain background context for now. Until stronger data or formal recommendations exist, I would not use progesterone, relaxin, or menstrual-cycle phase as a major basis for clinical decision-making, hormone manipulation, or training-periodization plans. For most athletes, the more reliable approach is still to prioritize established injury-prevention work, sensible load management, sleep, recovery, and individual symptom tracking.
Conclusion: Progesterone and Injury Risk
Progesterone and injury risk is not a simple story of one hormone making female athletes safer or more vulnerable. The strongest takeaway is more nuanced: progesterone, estrogen, relaxin, sleep, fatigue, training load, and individual symptoms all interact in ways that are biologically interesting but not yet clinically predictable.
For ACL injury specifically, the progesterone-dominant luteal phase appears to be associated with lower risk in several studies. At the same time, broader injury data suggest that the luteal phase may also bring poorer sleep, greater fatigue, and higher overall injury burden in some athletes. Both findings can fit together if we remember that ligament biology and whole-athlete recovery are not the same thing.
In practice, I would treat progesterone as useful context, not as a target for treatment or a basis for rigid cycle-based training plans. Athletes do not need to ignore their cycle, but they also should not be told that hormone phase alone can predict injury risk or dictate training. At least for now, there are no established recommendations to use exogenous progestins for injury prevention. Established injury-prevention work, sensible load management, adequate recovery, and individualized symptom tracking remain far more actionable than trying to optimize training around progesterone.
Bibliography
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5524267/
[2] https://pubmed.ncbi.nlm.nih.gov/16436538/
[3] https://pubmed.ncbi.nlm.nih.gov/31490339/
[4] https://journals.sagepub.com/doi/full/10.1177/0363546511413378
