A CT scan acquires X‑ray cross‑sectional images without added agents, showing anatomy and many abnormalities. A CT with contrast uses injected (iodine) and/or oral/rectal contrast to highlight blood vessels, organs, tumors and inflammation, improving lesion detection and tissue delineation. Contrast adds diagnostic clarity but carries small risks—allergic reactions and kidney effects—so allergies and kidney function are checked first.

Most knee CT scans do not require contrast — noncontrast CT is preferred for bones, fractures, alignment, and preoperative planning. IV contrast is reserved for concerns about infection, tumor, or vascular problems. CT arthrography uses intra‑articular contrast to better show cartilage, ligaments, or meniscal pathology. Your clinician will decide based on the diagnostic question, allergies, and kidney function.

Yes. CT scans give excellent bone detail and can detect fractures, joint alignment problems, advanced osteoarthritis, bone lesions and loose bodies; CT arthrography can better evaluate cartilage and joint surfaces. CT is less sensitive than MRI for soft-tissue injuries (ligaments, tendons, early cartilage damage). It’s especially useful for complex fractures and surgical planning but involves ionizing radiation.

Non‑ionic, low‑osmolar iodinated intravenous contrast is generally preferred for CT because it gives strong vascular and organ enhancement with fewer adverse reactions. Oral or rectal contrast (water‑soluble iodine or dilute barium) is used for bowel assessment. Choice depends on the clinical question, renal function, allergies, and risks — non‑contrast CT or alternative imaging may be used if contrast is contraindicated.

Single-contrast CT uses one contrast route (commonly IV or oral) to highlight either blood vessels or the GI lumen. Double-contrast CT uses two routes—typically oral/rectal plus IV—so both lumen and bowel wall/vasculature are well visualized. Double-contrast better detects and characterizes masses, inflammation, leaks and staging but takes longer and carries higher contrast-related risk.

You can refuse intravenous contrast for a CT scan — informed consent is voluntary. Refusing may reduce diagnostic accuracy and could alter management. Tell the radiologist/ordering clinician so they can offer alternatives (noncontrast CT, MRI, ultrasound), assess allergy or kidney risk, or use premedication/hydration. Document your decision and discuss benefits, risks and urgency before proceeding; in emergencies, clinicians may proceed with best-known care.