Objective.
To assess the change of joint effusion in suprapatellar recess using ultrasound (US) with/without isometric knee extension (IKE) in the patients with knee osteoarthritis.
Methods.
Twenty-three knees (9 right, 14 left) in 21 patients (18 women, 3 men; mean age, 64.0 years; range, 50-85) with knee osteoarthritis and joint effusion in suprapatellar recess were recruited at outpatient clinic from September 2019 to June 2020. Knee osteoarthritis was diagnosed and classified according to Kellgren and Lawrence (K-L) grade on radiograph. Joint effusion in suprapatellar recess was confirmed on ultrasound. Ultrasound examination was performed by a physiatrist who had 23 years of experience in musculoskeletal ultrasound. The anterior aspect of the knee was examined using ultrasound with the knee flexed at 20 degrees by placing a small pillow beneath the posterior aspect of the knee. The degree of knee joint effusion was measured at the maximal anterior-posterior (A-P) diameter of fluid collection in suprapatellar recess on longitudinal and transverse ultrasound images (Figure 1). Subsequently, the patient was instructed to extend the knees isometrically compressing the pillow maximally with dorsiflexion of ankle. During IKE, ultrasound measurement was repeated at the maximal point of joint effusion. After ultrasound examination, the joint effusion was aspirated in suprapatellar recess on ultrasound guidance, and the amount of joint effusion was measured. The difference of A-P diameter of joint effusion with/without IKE was evaluated by paired t test.
Results.
The severity of knee osteoarthritis was K-L grade I for 5 knees, grade II for 5 knees, and grade III for 13 knees. Baker cyst’s was found in 5 knees, and medial meniscal tear was diagnosed in 3 knees. The mean aspirated volume of knee joint effusion was 15.0 mL ± 11.0 (range: 3 – 45) (Table 1). Maximal A-P diameters of joint effusion with IKE (76.2 mm ± 33.4, and 75.1 mm ± 31.8) on longitudinal and transverse images were significantly greater than those (62.4 mm ± 30.0, 65.9 mm ± 30.3) without IKE (P < .05) (Table 2). There were no significant correlation between maximal A-P diameters and aspirated volume of joint effusion.
Conclusions.
Our results indicate that the volume of knee joint effusion in suprapatellar recess is increased during IKE in the patients with knee osteoarthritis. Therefore, ultrasound guided aspiration during IKE may be helpful for complete intra-articular aspiration of knee joint effusion. We recommend the IKE method for ultrasound guided aspiration in the patients with knee osteoarthritis and joint effusion.
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Knee position without/with isometric knee extension (A, B) and ultrasound measurement of knee joint effusion in suprapatellar recess on longitudinal (C, D) and transverse (E, F) images without/with isometric knee extension. The maximal diameters of joint effusion (white arrows) (D, F) in suprapatellar recess with isometric knee extension were greater than those without isometric knee extension (C, E). QT, quadriceps tendon; SPF, suprapatellar fat pad; PFF, prefemoral fat pad; F, femur.
Demographic data and imaging findings of the patients with knee osteoarthritis and joint effusion
Ultrasound measurement of knee joint effusion in suprapatellar recess with/without isometric knee extension
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