Dear Editor of Clinical Biomechanics,
We read with interest Kibsgård et al.'s above Clinical Biomechanics paper. Radiostereometric Analysis was performed to measure sacroiliac movements during the Active Straight Leg Raise (ASLR) in 12 patients with chronic Pelvic Girdle Pain (PGP). Of the patients, 8 had been diagnosed with bilateral, and 4 with unilateral sacroiliac pain. All were about to undergo sacroiliac fusion surgery.
We fully agree with Kibsgård et al. that this is an important field. About 5% of all pregnant women suffer from PGP that is sufficiently serious to warrant medical attention (Wu et al., 2004). Also athletes with groin pain may have PGP (Verrall et al., 2001), often in the form of osteitis pubis. Both groups of patients have difficulties performing the ASLR (Mens et al., 2006).
Contralateral to the side of the raising leg, Kibsgård et al. observed 0.8° backward rotation of the ilium with respect to the sacrum (range−0.3° to −1.3°, ‘minus’ for backward), and ipsilaterally on average 0.0° (range −1.0° to +0.5°). We congratulate Kibsgård et al. with this contribution to the field. Still, there are some questions.

Active straight leg raise, Pelvic girdle pain, Pubic symphysis, Sacroiliac joints,
Clinical Biomechanics
The clinical Biomechanics paper, to which this letter is a response, can be accessed online:
Department of Rehabilitation Medicine

Hu, H. (Hai), Prins, M.R. (Maarten R.), Wu, W.H, van Dieën, J.H, Xia, C. (Chun), Mens, J.M.A, & Meijer, O.G. (2018). “Movement of the sacroiliac joint during the active straight leg raise test in patients with long-lasting severe sacroiliac joint pain”. Clinical Biomechanics, 52, 100–101. doi:10.1016/j.clinbiomech.2018.01.008