Ultrasound-detected effusion-synovitis is associated with greater limb loading rate asymmetry during walking post-ACL...

Chronic inflammation and altered walking biomechanics are common after ACL reconstruction (ACLR) and contribute to the development of osteoarthritis. Clinically accessible techniques are needed to monitor inflammation (ultrasound-assessed effusion-synovitis) and walking biomechanics (force-measuring insoles), and they must improve the translation of these assessments and determine whether inflammation and walking biomechanics are related in patients after ACLR. This study aimed to determine the association between ultrasound-detected knee effusion-synovitis and limb loading asymmetries during walking in patients 1-5 years post-ACLR.

15 participants (9 women; age: 26 ± 6yrs; mass: 71 ± 15 kg; height: 173 ± 9 cm; months post-ACLR: 29 ± 13) were included in this cross-sectional study. Knee effusion-synovitis was assessed using a standardized protocol and graded using a validated scoring atlas (0 = absent, 1 = mild, 2 = moderate, 3 = severe) in the ACLR limb. Force-measuring insoles were used to capture the vertical ground reaction force (vGRF) during a one-minute treadmill walking trial. Limb symmetry indices (LSIs) were used to quantify limb loading asymmetry for the peak vGRF and the instantaneous loading rate (vGRF-LR). Spearman correlations determined whether effusion-synovitis grade was associated with peak vGRF and vGRF-LR LSI.

Effusion-synovitis was present in the ACLR limb of 13/15 (87 %) participants (Grade 0: n = 2; Grade 1: n = 8; Grade 2: n = 4, Grade 3: n = 1). Effusion-synovitis grade was not significantly associated with peak vGRF LSI (mean±sd: 98.0 ± 5.6; ρ = 0.38, p = 0.162), but was significantly associated with vGRF-LR LSI (98.2 ± 11.4; ρ = 0.55, p = 0.035).

Most participants 1-5 years post-ACLR have ultrasound-detected effusion-synovitis. Participants with more severe effusion-synovitis load their ACLR limb more rapidly. This study highlights the utility of clinically accessible techniques in assessing inflammation and walking biomechanics in ACLR patients.