Pelvic rehabilitation practitioners often focus on mechanical concerns such as diastasis recti, pelvic floor weakness, and altered load transfer. However, one foundational element that deserves equal attention in the postpartum period is the ongoing effect of hormonal shifts on connective tissues and joints.

Even after delivery, hormones such as relaxin, estrogen, and progesterone continue to influence tissue behavior, joint mobility, and the body's response to rehabilitation. Understanding how these hormones affect ligament laxity, collagen turnover, and neuromuscular control helps clinicians design safer and more effective recovery programs.

Hormonal Changes in Pregnancy and Early Postpartum
Relaxin is produced by the corpus luteum and placenta, and rises significantly during pregnancy. It is known for its role in “relaxing” muscles and ligaments, especially in the pelvis, to facilitate childbirth. Estrogen and progesterone also rise and modulate connective-tissue metabolism and receptor expression in ligaments.

A recent review highlights that pregnancy-associated hormonal fluctuations (relaxin, estrogen, progesterone) contribute to increased joint laxity (Yalçınkaya et al., 2025). These hormonal effects do not cease abruptly at delivery; they taper variably and may persist for months postpartum, meaning joint and tissue behavior remains altered during rehab.

Hormones Affect Connective Tissue and Joint Mechanics
At the cellular level, relaxin increases the activity of matrix metalloproteinases (MMPs) such as MMP-1, -9, and -13, which degrade collagen and weaken ligament/tendon architecture (Parker et al., 2-22). Estrogen and progesterone increase expression of relaxin receptors in ligaments, amplifying these effects (Yalçınkaya et al., 2025).

In animal and human tendon studies, both relaxin and estrogen have been shown to reduce tendon stiffness and increase compliance, which can reduce load tolerance (Danos et al., 2023). The net mechanical effect is increased joint mobility (or perceived laxity), reduced passive stability, and a greater need for neuromuscular control to compensate.

Clinically, this manifests as more “loose-feeling” joints, increased cushioning of movement, greater reliance on muscular control for stability, and potentially slower progress of load-transfer training. A prospective cohort during pregnancy found associations between estrogen changes and increased low-back/pelvic-girdle pain and disability (Daneau et al., 2025). Although postpartum longitudinal data are sparse, the same mechanisms are likely to persist into the early postpartum period and influence rehab.

Implications for postpartum rehabilitation of joints

1. Assessment and monitoring: Include joint laxity screening (e.g., Beighton score or joint-specific tests) and ask the client about subjective joint “giveness” or instability. Recognize that normal endpoints may be slower to return.
2. Loading progression: Because connective tissues are in a transiently weakened state, adopt more conservative load progressions. Emphasize neuromuscular control (motor control, stability) before heavy mechanical loading. Use subsets such as closed-chain, low-velocity, high-control activities.
3. Tailored timeline: Do not assume pre-pregnancy tissue behavior has returned simply because the organ-based recovery period has ended. A busy schedule, hormonal fluctuations (including lactation, menses return) may continue to modulate tissue mechanics.
4. Patient education: Explain that “it’s not just about the tummy and pelvic floor” but that “your ligaments and joints are still adjusting.” This can help set realistic expectations and foster adherence to graded rehab.
5. Coordination with other practitioners: Ensure communication with obstetric, primary-care, and sports-medicine colleagues about longer-term musculoskeletal implications of hormonal and biomechanical changes. As one review concluded, many women are at elevated risk for persistent joint instability and possible long-term sequelae such as early osteoarthritis (Yalçınkaya et al.., 2025).

Case example
A 34-year-old primipara at 10 weeks postpartum presents with “clicking” in the pubic symphysis region when lifting her 9-month-old toddler and reports a sense of “unstable hips” when stepping sideways. On assessment, she has a Beighton score of 5/9 (with bilateral thumb-to-forearm and elbow hyperextension). She also reports previous hip discomfort in adolescence.

Given her history and findings, you design a graduated program: phase 1 focused on pelvic-floor activation + hip stability in non-weight-bearing by week 12; phase 2 at week 16, introducing unilateral step-downs with low amplitude; phase 3 at week 20, adding higher load functional tasks (carrying child + step).

You monitor joint symptoms, ensure neuromuscular control precedes full load, and educate her regarding ligamentous recovery timeline (~6-12 months). You explain that although the baby is 9 months old, her connective tissues may still be adjusting to hormone-mediated changes.

Conclusion
Hormonal recovery is a critical but sometimes overlooked element of postpartum rehabilitation. The lingering influence of relaxin, estrogen, and progesterone shapes how connective tissues behave and respond to loading. By integrating hormonal awareness into clinical decision-making, pelvic health practitioners can enhance precision, promote safety, and improve long-term functional outcomes. Recovery after childbirth is not limited to muscle or fascia; it is a systemic process involving hormones, tissues, and time.

For clinicians interested in expanding their postpartum rehabilitation skills, consider registering for the upcoming Postpartum Rehabilitation Remote Course scheduled for December 13-14. This course covers acute postpartum management, mental health screening, and musculoskeletal considerations. Participants will learn to modify examinations and interventions for the relevant stages of postpartum recovery. In addition to abdominal wall considerations, typical spine and extremity dysfunctions will be addressed. The course includes instruction on postpartum exercise and return to fitness, with labs covering external perineal screening as well as techniques for the abdominal wall, spine, and ribs, and upper and lower quarter dysfunction.

References

1. Yalçınkaya, B., Sezgin, E. A., Saçıntı, K. G., & Özçakar, L. (2025). Neuromusculoskeletal disorders in pregnancy revisited. Journal of Joint Diseases and Related Surgery, 36(3), 741-750.
2. Parker, E. A., Meyer, A. M., Goetz, J. E., Willey, M. C., & Westermann, R. W. (2022). Do Relaxin Levels Impact Hip Injury Incidence in Women? A Scoping Review. Frontiers in Endocrinology, 13, 827512. https://doi.org/10.3389/fendo.2022.827512
3. Danos, N., Patrick, M., Barretto, J., Bilotta, F., & Lee, M. (2023). Effects of pregnancy and lactation on muscle-tendon morphology. Journal of Anatomy, 243(5), 860-869. https://doi.org/10.1111/joa.13916
4. Daneau, C., Nougarou, F., Abboud, J., Ruchat, M., & Descarreaux, M. (2025). Changes in pregnancy-related hormones, neuromechanical adaptations and clinical pain status throughout pregnancy: A prospective cohort study. PLOS ONE, 20(2), e0314158. https://doi.org/10.1371/journal.pone.0314158