Changes in the suprapatellar recess according to knee posture during ultrasound examination. (A) When the knee is in extension, the quadriceps tendon is relaxed, causing the suprapatellar recess to collapse. (B) When the knee is flexed at 20∼30 degrees, the quadriceps tendon becomes taut, leading to expansion of the suprapatellar recess.|@|~(^,^)~|@|(A) The presence of a slight effusion in the suprapatellar recess bursa is a finding that can be observed even in a normal knee joint. (B) An effusion thickness of 5 mm or more between Hoffa’s fat pad and the prepatellar fat pad is considered an abnormal increase in effusion.|@|~(^,^)~|@|In cases of meniscus injury, localized hypoechoic or anechoic lesions can be observed within the meniscus ((A) Horizontal tear of medial meniscus, (B) Vertical tear of lateral meniscus). (C) Meniscal cysts are visualized on ultrasound as hypoechoic or anechoic cystic structures adjacent to or within the meniscus. (D) This image shows medial meniscus protrusion.|@|~(^,^)~|@|In quadriceps femoris tendinopathy, swelling characterized by hypoechoic changes can be observed within the tendon and surrounding soft tissues on ultrasound. Doppler examination may also demonstrate increased blood flow. (A) Normal, (B) Quadriceps tendinopathy.|@|~(^,^)~|@|The retraction sign is observed due to a full-thickness tear of the quadriceps femoris tendon.|@|~(^,^)~|@|Ultrasound findings of patellar tendinopathy. Hypoechoic or anechoic swelling is observed in the deep portion of the proximal patellar tendon (A). Additionally, increased blood flow can be observed on Doppler examination (B).|@|~(^,^)~|@|Ultrasound findings of Osgood-Schlatter disease. Swelling is observed in the soft tissues and cartilage of the tibial tuberosity, as well as in the distal patellar tendon. Additionally, hyperechoic bone fragments are observed (arrow).|@|~(^,^)~|@|Ultrasound findings of iliotibial band tendinopathy. Hypoechoic swelling of the iliotibial band tendon, surrounding inflammation, and evidence of bursitis in the deep portion of the tendon above the lateral femoral condyle (LFC) are observed.|@|~(^,^)~|@|Stages of medial collateral ligament (MCL) injury: (A) Stage 1 involves minimal tearing without clinical instability of the ligament. (B) Stage 2 involves partial MCL tear with accompanying ligament instability. Hypoechoic effusion is observed around the thickened area of the ligament. (C) Stage 3 refers to the complete rupture of the medial collateral ligament. Ultrasound reveals hypoechoic effusion or hematoma filling the disrupted hyperechoic ligament.|@|~(^,^)~|@|(A) Ultrasound findings of a normal lateral collateral ligament (LCL). (B) Ultrasound findings of LCL injury. The ligament appears hypoechoic, thickened, or demonstrates an irregular structure and may be observed as a completely disrupted band-like appearance.|@|~(^,^)~|@|Ultrasound findings of the superficial (A) and deep (B) prepatellar bursitis.|@|~(^,^)~|@|Ultrasound findings of pes anserine bursitis. A hypoechoic lesion can be observed between the tendons.|@|~(^,^)~|@|Ultrasound findings of Baker’s cyst. Longitudinal view (A) and transverse view (B). The entrance of the synovial cyst can be observed between the semimembranosus tendon and the medial head of the gastrocnemius muscle (GMH). This entrance is connected to the joint cavity, and when there is an increase in joint effusion, the fluid can accumulate in the cyst through this entrance.|@|~(^,^)~|@|Ultrasound-guided knee intra-articular injection. The transducer is placed on the superior aspect of the patellar tendon, facing the suprapatellar recess between Hoffa’s fat pad and the prefemoral fat pad. The needle is inserted towards the suprapatellar recess using an in-plane approach from either the medial (A) or lateral (B) side.|@|~(^,^)~|@|Ultrasound-guided aspiration of Baker’s cyst. The transducer is positioned longitudinally on the medial aspect of the calf, and the needle is inserted from the distal aspect to confirm its placement within the cyst before aspiration (A). If a distal approach is challenging, the transducer is positioned transversely, and the needle is inserted from the lateral aspect of the cyst (B).

Clinical Pain 2023;22:14~21 https://doi.org/10.35827/cp.2023.22.1.14