MRI vs. CT
Three imaging tools — X-ray, CT, and MRI — each shows different things and has different uses in orthopedics.
X-ray: the starting point
X-rays are the first imaging we typically order. They use radiation to create a 2D picture of bones and dense structures. X-rays are:
- Quick — seconds to minutes.
- Cheap — the least expensive imaging option.
- Good for bone — show fractures, dislocations, alignment, arthritis, bone spurs clearly.
- Poor for soft tissue — can’t see tendons, ligaments, cartilage, or muscles.
- Lower radiation exposure — but still uses radiation.
An X-ray is the right starting point for suspected fractures, suspected arthritis, or any bone question. But if soft-tissue injury is suspected, we need more.
CT (computed tomography): detailed bone anatomy
CT (or CAT scan) takes many X-ray slices and reconstructs them into 3D images. It’s much more detailed than a flat X-ray:
- 3D reconstruction — can rotate and examine bone from all angles.
- Excellent for complex fractures — shows exactly how the bone pieces fit (or don’t) so surgeons can plan reconstruction.
- Good for subtle bone detail — bone tumors, stress fractures, tiny fragments.
- Faster than MRI — minutes instead of 30–45 minutes.
- Higher radiation — more than a regular X-ray, so we use it judiciously.
- Still poor for soft tissue — tendons, ligaments, and cartilage don’t show well.
CT is the gold standard for complex fractures (especially those involving joints), for surgical planning of complicated breaks, and for evaluating bones in great detail when X-rays aren’t enough.
MRI (magnetic resonance imaging): soft tissue champion
MRI uses magnetic fields and radio waves to create detailed images. It’s exceptional for soft tissue:
- Excellent for soft tissue — shows tendons, ligaments, cartilage, meniscus, labrum, muscles, nerves, discs in beautiful detail.
- No radiation — completely safe; no X-rays involved.
- High resolution — often the most detailed images available.
- Contraindicated with metal implants — certain pacemakers, metal implants, or shrapnel mean no MRI (always ask the patient).
- Takes longer — 30–45 minutes; must lie still in a tube (not great for claustrophobic patients).
- Expensive — more costly than X-ray or CT.
MRI is the right choice for suspected ligament or tendon tears, for rotator cuff injuries, for meniscal tears in the knee, for disc herniations in the spine, for stress fractures early in their course, and for any problem where soft-tissue detail matters.
Practical decision-making
Suspected fracture? Start with X-ray. If it’s complex and surgery is likely, follow with CT for 3D detail.
Suspected torn rotator cuff, ligament, or meniscus? MRI is the right first step (after clinical exam). X-rays won’t show the tear.
Suspected stress fracture that’s not visible on X-ray yet? MRI is more sensitive early on; bone scan or CT can also detect it.
Spine pain with possible nerve compression? MRI shows the disc, the spinal cord, the nerve roots, and compressed structures beautifully.
Simple knee effusion (fluid) or bruising? Sometimes MRI is overkill. Clinical judgment and X-rays may be enough to guide initial treatment.
Ultrasound: the real-time option
We should mention ultrasound, though it’s in a different category. Ultrasound uses sound waves to image soft tissue live. It’s operator-dependent (the skill of the person holding the probe matters), but it can visualize tendons, bursas, joint fluid, and nerves in motion—and it’s excellent for guiding injections into joints or tendon sheaths. No radiation, no metal contraindications, inexpensive. For superficial structures, ultrasound is often the first choice at our clinic.