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These 10 free MSK-ST questions are organized by exam domain, so you can see how each part of the POCUS - Musculoskeletal Soft Tissue (MSK-ST) blueprint is tested. Reveal the answer and explanation under each question.
A 9-year-old has persistent pinpoint tenderness beneath a healed fingertip puncture. The skin is intact. With a high-frequency linear probe directly on the finger, the suspected foreign body lies in the poorly resolved near field, and even light contact is painful. Which modification addresses both problems?
Correct answer: B - Scan through a water bath with the linear probe held above the skin.
After several days of flooring work, a patient develops swelling centered over the patella. Longitudinal and transverse scans show fluid between the subcutaneous tissue and the anterior surface of the patella. The suprapatellar recess is not distended. In which compartment is the fluid located?
Correct answer: D - Prepatellar bursa
While mapping a forearm mass, the examiner encounters an adjacent oval structure containing multiple hypoechoic fascicles separated by bright connective tissue. Following it proximally reveals a continuous fascicular cord rather than a discrete nodule. What structure should be marked on the image?
Correct answer: A - Peripheral nerve
A runner's mildly painful Achilles tendon contains a dark segment where the tendon curves toward its insertion. A transverse image shows preserved architecture, and there was no sudden injury or loss of active plantar flexion. Before calling the dark segment a tear, the examiner should:
Correct answer: A - Rock the transducer to insonate that segment perpendicular to its fibers.
A painful groin lump appears two days after femoral arterial catheterization. Color Doppler shows flow within a sac beside the artery. At a narrow connecting channel, spectral Doppler records flow from the artery into the sac during systole and back toward the artery during diastole. This waveform is characteristic of:
Correct answer: C - A pseudoaneurysm communicating with the femoral artery
An approximately ellipsoid fluid collection is measured on follow-up using the same acquisition technique as before. Its maximum length is 4.0 cm and width is 2.0 cm. Along the line of maximal anteroposterior thickness, the near wall is 0.8 cm below the skin and the far wall is 2.3 cm below the skin. The previous volume estimate was 10.0 mL. Using V = 0.52 × length × width × anteroposterior thickness, with dimensions in centimeters and 1 cm³ = 1 mL, which report correctly describes the change? Round volumes to the nearest 0.1 mL.
Correct answer: D - Current volume 6.2 mL; decrease of 3.8 mL.
An otherwise healthy 32-year-old has three days of increasing redness and tender induration over the lateral upper arm, without trauma or palpable fluctuance. Ultrasound in two planes identifies a 2.8-cm subcutaneous cavity with mobile debris and a hyperemic rim but no internal flow. No nerve or vessel crosses the proposed drainage approach. The patient is afebrile and can tolerate local anesthesia. How should the cavity be addressed?
Correct answer: C - Perform incision and drainage under local anesthesia.
Three days after striking her thigh against a table, a 76-year-old receiving oral anticoagulation notices bruising and a tender lump. She has no skin break or fever. Ultrasound demonstrates a heterogeneous collection within the muscle, with no reproducible internal flow after Doppler optimization. Her hemoglobin and vital signs are unchanged. The history most strongly favors:
Correct answer: B - A traumatic hematoma
Fever and refusal to bear weight prompt hip ultrasound in a 5-year-old. The anterior joint capsule is distended by anechoic fluid; no debris is visible. A clinician suggests that the clear fluid appearance establishes transient synovitis. Which assessment of that conclusion is correct?
Correct answer: A - The effusion is demonstrated, but its infectious status remains undetermined.
A patient with diabetes has rapidly worsening calf pain that extends well beyond a small area of erythema. The calf is increasingly tender despite initial treatment, and the patient is tachycardic. POCUS shows subcutaneous edema and fluid tracking along deep fascia, but no gas or discrete abscess. Intravenous antibiotics and resuscitation have been started. What takes priority now?
Correct answer: C - Request immediate surgical assessment for suspected necrotizing infection.
The MSK-ST exam also covers these domains. Drill them in the full free practice test:
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