This study aimed to evaluate the dynamics of the medial meniscus during knee flexion–extension by ultrasonography and compare them with MRI findings to confirm the usefulness of ultrasonography for evaluating early knee osteoarthritis (KOA). In total, 100 patients were diagnosed with early KOA using clinical and radiographical findings. Dynamic ultrasonographic evaluation and MRI were performed in all patients. Medial meniscal extrusion (MME) and medial meniscal tears were evaluated via ultrasonography and MRI. Abnormal MME was defined as MME > 2 mm on ultrasonography during knee extension. Patients with abnormal MME were divided into two groups: a decrease group (group D) and a non-decrease group (group N). Age, sex, absence or type of meniscus tear, and MME were compared between the two groups. Of the 100 patients, 75 demonstrated MME > 2 mm at knee extension. MME at all assessment positions using ultrasonography and MRI were significantly greater in group N (n = 34) than that in group D (n = 41). Medial meniscus posterior root tears or radial tears were observed in most cases in group N. A lack of decrease in MME from 0° to 90° of flexion on ultrasonography was a characteristic finding in patients with a loss of meniscal hoop function.

This study aimed to identify factors affecting anterior knee pain (AKP) after anterior cruciate ligament reconstruction (ACLR) with hamstring tendon autograft using ultrasonography. Forty-two patients were evaluated by ultrasound, 6 months after ACLR. The thickness of the superficial part of the infrapatellar fat pad was measured, as well as the thickness change ratio between the two angles. Color Doppler evaluated the rate of blood flow in the fat pad. AKP was assessed with the Kujala Scale. The correlations between AKP and age, body mass index, the thickness change ratio, and the grade of increased blood flow were examined. Independent variables showing significant correlations with AKP were used for multiple linear regression analysis. There were significant correlations between AKP and age (r = − 0.68), body mass index (r = − 0.37), the thickness change ratio of the fat pad (r = 0.73) and the grade of increased blood flow (r = − 0.42), respectively. Age and the thickness change ratio of the fat pad affected the AKP score (R2 = 0.56). After ACLR, older age and a decrease in the thickness change ratio of the superficial area of the infrapatellar fat pad appear to affect post-operative AKP after 6 months.

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To compare the clinical results and ligamentization of anterior cruciate ligament reconstruction (ACLR) between skeletally immature and mature patients. Two-hundred-and-two patients who underwent primary ACLR were evaluated retrospectively. The clinical outcomes were compared between skeletally immature (immature group 1, n = 27) and mature (control group 1, n = 175) groups. Graft ligamentization of the reconstructed anterior cruciate ligament (ACL) using magnetic resonance imaging (MRI) signal intensity at 6 months postoperatively was compared between immature group 2 (n = 16), which included participants from immature group 1, and control group 2 (n = 32), created by recruiting data-matched controls from control group 1. Immature group 1 had significantly higher revision (14.8%) and pivot shift test positive (22.2%) rates than control group 1 (2.9% and 4.0%, respectively) (P = 0.020 and 0.003, respectively). The signal intensity in immature group 2 were significantly higher at the mid-substance and distal site of the reconstructed ACL than those in control group 2 (P = 0.003 and 0.034, respectively). Skeletally immature patients had higher graft revision and residual rotational laxity rates. Reconstructed ACL in skeletally immature patients showed higher signal intensity on MRI at 6 months postoperatively.