Ultrasound of the knee visualizes superficial soft tissues: tendons (patellar, quadriceps), ligaments, bursae, synovium, joint effusion, Baker’s cysts, and periarticular inflammation. It detects tendon tears, bursitis, fluid collections and uses Doppler to show increased blood flow from active inflammation. It is limited for seeing bone, deep intra‑articular cartilage or meniscal tears, so MRI may be needed.

For most unexplained knee pain, MRI is best: it visualizes ligaments, menisci, cartilage and bone marrow. X‑rays are first‑line to detect fractures or arthritis. CT is used for complex fractures and detailed bone anatomy. Ultrasound assesses superficial tendons, bursae and effusions. Choice depends on the clinical exam and suspected injury—discuss the most appropriate scan with your clinician.

A diagnostic knee ultrasound typically takes about 10–30 minutes for the scan itself. Including registration, positioning and a brief clinical review, expect a total appointment time of roughly 20–45 minutes. More complex assessments (multiple structures, guided injections) or additional imaging review may extend the visit. No special preparation is usually required; wear loose clothing and follow any clinic-specific instructions.

Wear loose shorts or clothing so the knee is easily accessible; remove jewelry and dressings; avoid creams, oils or lotions on the skin. Bring previous imaging or reports and a list of medications. You usually do not need to fast or stop medicines (confirm if on blood thinners). Arrive early and bring mobility aids if you use them. The exam is short and painless with gel applied.

A doctor orders a knee ultrasound to evaluate soft tissues and fluid—detecting effusions, bursitis, Baker’s cysts, tendon or ligament tears, and synovitis. Ultrasound offers dynamic, real‑time assessment, Doppler detection of inflammation, and guidance for aspiration or injection. It’s useful for locating cysts, monitoring healing, and identifying superficial masses or calcifications when MRI isn’t required or to guide procedures.

Knee ultrasound can detect features of arthritis—joint effusion, synovial inflammation or hypertrophy, Baker’s cysts, and superficial erosions—but it is limited for assessing deep cartilage loss and joint‑space narrowing. It’s operator‑dependent and often used alongside X‑ray (for bony changes) or MRI (best for cartilage and bone marrow). Ultrasound helps guide injections and evaluate inflammation but isn’t definitive alone.