Pregnancy causes a number of changes to a woman’s musculoskeletal system to create space for the developing fetus. Additionally, biomechanical adaptation as the center of gravity moves forward is critical to pregnancy. Adaptations occur especially in soft tissues, joints and consequently the posture of the body as a whole. Increased levels of relaxin, estrogen and progesterone cause relaxation of soft tissues. In addition, there are musculoskeletal changes, such as increased lumbar lordosis, posterior inclination of the sacrum, instability of the lower limbs, increased mobility of the pelvic joints. All these factors adversely affect the health and quality of life of pregnant women, causing difficulties in daily activities, increasing the risk of falling and/or causing low back/pelvic girdle pain (PGP) (1).
The cause of PGP is not yet fully understood. Pain/injury of the lower back and pelvis before pregnancy has been reported as the most important risk factor. In addition, studies have shown that pregnancy-related PGP results from increased mobility of the sacroiliac joints (SIJ) due to hormonal and biomechanical changes. Due to the position of the pelvis, the sacroiliac joint is an overloaded area with limited mobility. Optimal stability of the sacroiliac joint is provided by its anatomical structure (closed shape) and the surrounding soft tissues (adhesion). During pregnancy, the mobility of the sacroiliac joint increases due to the weakening of the adhesion associated with the hormone-dependent relaxation of the soft tissues and the disruption of the “closed form” as a result of the increasing pelvic forward tilt. However, hormonal factors have also been shown not to cause sacroiliac joint pain. Interestingly, there is no clear relationship between serum relaxin levels and peripheral joint laxity and PGP formation (2).
Another region where postural changes are observed in pregnant women is the feet. It has been noted that increased body weight and pregnancy hormones decrease the height of the arches of the feet, which in turn increases the bearing surface. This may be accompanied by changes in the anthropometric characteristics of the foot (length, width, increase in volume, etc.). Similarly, it has been shown that the stiffness of the ankles increases in pregnant women in order to maintain balance. Changes in the structure of the foot can affect the lower limbs, pelvis and spine (the entire biomechanical chain). Several studies have found a relationship between the foot and the lumbar spine, as well as foot and pelvic pain. As far as we know, the effect of pregnancy on the biomechanical (tone-Hz and stiffness-N/m) and viscoelastic properties of the foot tissue and whether this is related to the manifestation of PGP has not been adequately studied. The plantar fascia is one of the most important structures that maintains the height of the arch of the foot and performs its functions in interaction with the Achilles tendon. Therefore, the tissue properties of the fascia and Achilles tendon are important from the perspective of foot function. In light of these studies, pregnancy is thought to alter foot tissue properties. These changes may also affect the upper segments through the biomechanical chain, contributing to the development of PGP (3).
Martyna Kasper-Jędrzejewska
References:
- Kazma JM, van den Anker J, Allegaert K, Dallmann A, Ahmadzia HK. Anatomical and physiological alterations of pregnancy. J Pharmacokinet Pharmacodyn. sierpień 2020;47(4):271–85.
- Clinton SC, Newell A, Downey PA, Ferreira K. Pelvic Girdle Pain in the Antepartum Population: Physical Therapy Clinical Practice Guidelines Linked to the International Classification of Functioning, Disability, and Health From the Section on Women’s Health and the Orthopaedic Section of the American Physical Therapy Association. J Women’s Health Phys Ther. maj 2017;41(2):102–25.
- Kablan N, Can M, Ayvacı H, Gerçek N, Eroğlu ZA, Özgit B, i in. Biomechanical and Viscoelastic Properties of the Achilles Tendon and Plantar Fascia in Pregnant Women with Pelvic Girdle Pain: A Case–Control Study. Women Health. 15 czerwiec 2022;0(0):1–12.
