Ultrasound characteristics of the lateral retinaculum in 10 patients with patellofemoral pain syndrome compared to healthy controls

Summary Background Histopathologic changes of the lateral retinaculum are described in patients with patellofemoral pain syndrome (PFPS). No information is available on the presence of structural changes of the lateral retinaculum on ultrasound examination in patients with PFPS. Purpose To describe ultrasound characteristics and colour Doppler findings in patients with unilateral PFPS and in healthy controls. Methods 10 patients with unilateral PFPS and 10 healthy control subjects underwent ultrasound and colour Doppler examination of the lateral retinaculum of both knees. Thickness of the lateral retinaculum was measured at three predefined locations. In addition presence of neovascularisation was assessed. Results Thickness of the lateral retinaculum of both affected (mean [SD] of three locations 4.0 [1.4] mm, 95%CI: 1.2–6.8) and asymptomatic (3.7 [0.8] mm, 95%CI: 2.1–5.3) knees was increased in the patient group compared to the control subjects (3.0 [0.1] mm, 95%CI: 2.8–3.2), although not reaching statistical significance. Positive colour Doppler signals of the lateral retinaculum were found in 4 patients and in none of the control subjects (4/10 versus 0/10; 2 × 2 Fisher's exact test 1-tailed p = 0.0433; 2-tailed p = 0.0866; mid p value = 0.0217). Conclusions The results of these measurements indicate a trend towards a larger thickness of the lateral retinaculum and showed neovascularisation measured by ultrasound and colour Doppler examination in patients with PFPS. The larger thickness of the lateral retinaculum on ultrasound examination was found in both affected and in asymptomatic knees of the patients, supporting the concept that PFPS is a bilateral rather than a unilateral disorder. Further research is needed to unravel the role of the lateral retinaculum in pathogenesis of PFPS and to clarify the role of the lateral retinaculum as a target for therapy in patients with PFPS.