Pregnancy Results in Lasting Changes in Knee Joint Laxity.
Stacey R Chu, Elizabeth H Boyer, Bruce Beynnon and 1 others
PMID 29964215WHAT IT FOUND
Pregnant women measured in first trimester and about 5 months postpartum had lasting knee changes, but not the expected increase.
Side-to-side and posterior laxity decreased; anterior laxity increased in first-time mothers. The changes were small, and no knee arthritis outcome was measured.
Key findings
01Knee laxity decreased by 20-22% in the coronal plane and by 51% in the posterior direction in both primiparous and multiparous women.
02Anterior knee laxity increased in primiparous women and tended to decrease in multiparous women.
03Posterior knee compliance decreased for both parity groups, while anterior compliance increased for primiparous women and overall but not for multiparous women.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study used first-trimester values as a stand-in for pre-pregnancy knees because it did not measure before pregnancy. 50 women completed baseline, but 48 had usable postpartum data. The magnitude of change was small compared with day-to-day measurement variability. The study did not measure knee structures directly or follow participants to knee osteoarthritis, so it cannot show that the changes cause disease. Postural changes during pregnancy were not measured, so they could have contributed to the knee findings. Age differed between primiparous and multiparous participants.
Declared interests
No author conflicts were declared in the supplied text. The article lists NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not conclude that pregnancy increases knee laxity or causes knee osteoarthritis. The study did not measure knees before pregnancy or follow participants to arthritis, and the changes were small relative to measurement variability.