Longitudinal ultrasound and clinical follow-up of Baker's cysts injection with steroids in knee osteoarthritis.

This study was conducted to assess ultrasound (US) and clinical changes of Baker's cyst (BC) of patients with knee osteoarthritis (OA) after steroid injection. Patients with knee OA complicated with symptomatic BC (40) were treated with US-guided direct (posterior) aspiration. The injection of 40 mg triamcynolone acetonide was in 20 patients direct into the BC and in other 20 subjects intra-articular (anterior). BC diameters (longitudinal, transverse, and thickness) were measured and followed up with US at baseline, 2, 4, and 8 weeks after injection. Swelling, pain, and range motion were scored at clinical examination with Rauschning and Lindgren classification (RLC, since 0 normal to 3 maximal signs). All US measures of BC and RLC significantly decreased after treatment, in comparison to baseline (p < 0.001) and during the follow-up, did not change through the time (no significant difference between 2, 4, and 8 weeks). At 4 and 8 weeks, diameters measured at US are lower when BC is directly infiltrated in comparison to intra-articular injection (p < 0.01). US steroid direct injection reduces US measures and clinics of BC in knee OA, in particular, when steroid is directly infiltrated into BC.