Which Scan Do You Need for Back, Hip or Knee Pain?
The right scan depends on the clinical question, not just where it hurts. X-rays show bones. MRI shows soft tissue such as discs and ligaments. CT gives detailed bone cross-sections. An EOS standing scan shows your whole-body alignment under load, with about 90% less radiation than a standard X-ray, around ten times less. Start with the question your clinician needs answered, then choose the tool that answers it.
Key takeaways
- Every scan type is good at something different. No single scan answers every question.
- Bones and alignment need X-ray or EOS. Soft tissue, discs and nerves need MRI.
- Lying-down imaging can hide alignment problems that only appear when you stand.
- You do not always need a GP referral. A free video consultation can help you decide.
- For details on cost, safety and what to expect, see our frequently asked questions.
If you have had pain for weeks or months and are not sure which scan to ask for, you are not alone. There are several types of medical imaging, each designed for a different job. Choosing the wrong one can mean wasted time, unnecessary radiation, or a result that still does not explain your symptoms.
This page explains the most common scans in plain language and helps you work out which one fits your situation.
A note on MRI. EOS shows bones, joints and alignment beautifully. For soft tissue, discs or nerves, MRI is usually the better tool. Often people need both. If you are unsure, a consultation can help you decide.
What are the main types of medical scans for pain?
There are six common imaging tools used for musculoskeletal problems. Each excels at a specific task.
Should I get an X-ray, MRI or CT for my pain?
It depends on what your clinician needs to see. The table below gives a quick guide. For a deeper look at how EOS stacks up, read about EOS compared with x-ray, CT and MRI.
| Scan | Best for | Position | Radiation | Soft tissue? |
|---|---|---|---|---|
| X-ray | Fractures, arthritis, bone spurs | Lying or standing (single area) | Low | No |
| MRI | Discs, ligaments, nerves, cartilage | Lying down | None | Yes |
| CT | Complex fractures, 3-D bone detail | Lying down | Higher | Limited |
| EOS | Whole-body alignment, leg length, pre-surgery planning | Standing | Very low (about 90% less than X-ray) | No |
| Ultrasound | Tendons, bursae, guided injections | Various | None | Yes (superficial) |
| DEXA | Bone density / osteoporosis screening | Lying down | Very low | No |
Why does standing up during a scan matter?
Standing up loads your skeleton with your full body weight. That changes everything. When you lie down for a standard X-ray, CT or MRI, gravity is removed and your muscles relax. A tilted pelvis may look level. A curved spine may straighten. A knee that tracks poorly under load may appear normal.
Your body works as a connected chain from your feet to your head. A problem in one area, such as a slight leg-length difference or a shifted pelvis, can force another area to compensate. That compensation often shows up as pain somewhere else entirely. A standing, whole-body EOS scan captures this full picture in a single image, so the real cause of your symptoms is far less likely to be missed.
For more on how this applies to specific areas, see our back pain clinic page or our guide to hip pain and alignment.
Not sure whether a standing alignment scan is right for you? A short video call with our team can help you check which scan suits you.
Book a free video consultationHow do I decide which scan I actually need?
Start with the clinical question, not the technology. Here is a simple way to think about it.
Define the question
Is the problem a bone issue (fracture, arthritis, alignment) or a soft-tissue issue (disc, ligament, nerve)? The answer narrows your options immediately.
Consider position
Does your pain get worse when you stand or walk? If so, a lying-down scan may miss what a standing scan would show.
Think about the whole chain
If single-area imaging has already come back "normal" but you still have symptoms, a whole-body alignment view might reveal a compensatory problem elsewhere.
Ask a professional
A radiographer or clinician can match the right scan to your specific situation. At ScanAlign, private standing imaging in London, we offer a free video consultation to help you work this out before you commit.
- Long-standing back, hip or knee pain with no clear diagnosis
- Pain that worsens on standing or walking
- A suspected leg-length difference or pelvic tilt
- Pre- or post-surgical alignment questions
- You suspect a disc bulge, nerve compression or ligament tear (MRI is usually better)
- You need a complex fracture mapped in 3-D (CT is usually needed)
- You are checking bone density (a DEXA scan is the right tool)
Red-flag symptoms. If you have sudden numbness, weakness, or loss of bladder or bowel control alongside back or leg pain, do not wait for any scan. Contact your GP, call 111 or go to A&E straight away.
Frequently asked questions about choosing a scan
It depends on the suspected cause. If the concern is arthritis, alignment or a fracture, an X-ray or standing EOS image is a good first step. If a ligament, meniscus or cartilage injury is suspected, MRI is usually more appropriate because it images soft tissue in detail.
For disc or nerve problems, MRI is generally the first choice. For spinal alignment, scoliosis or posture-related back pain, a standing X-ray or EOS scan is more revealing because it captures your spine under load. Many people benefit from both.
An X-ray can show arthritis and joint-space narrowing. MRI is better for labral tears and early cartilage damage. If your clinician suspects the pain is linked to pelvic tilt or alignment, a standing EOS scan shows how the hip sits relative to the whole skeleton.
Neither is universally better. CT excels at detailed bone imaging and is quicker to perform. MRI excels at soft tissue. The right choice depends entirely on the clinical question being asked.
An EOS scan takes a full-length, standing X-ray from your head to your feet in a single pass. It uses about 90% less radiation than a standard X-ray, around ten times less. Unlike a regular X-ray that captures one area, EOS shows how your entire skeleton lines up under your own body weight.
No. ScanAlign is a private, self-pay clinic. You can self-refer. We recommend starting with a free video consultation so we can confirm whether an EOS scan is the right choice for your situation.
An EOS scan uses about 90% less radiation than a standard X-ray, around ten times less. This makes it one of the lowest-dose skeletal imaging options available.
An EOS scan images you from head to feet in one standing pass, giving a complete view of skeletal alignment. Standard X-rays, MRI and CT typically focus on a single area at a time.
For current pricing and what is included, please visit our frequently asked questions page.
You stand still inside the scanner for around 15 to 20 seconds while the image is taken. There is no enclosed tube and no loud noise. You can wear normal clothing without metal fastenings. Full details are on our frequently asked questions page.
Still not sure which scan is right for you?
A short video call with our team can help you work out the best next step, with no obligation.
Book a free video consultationAuthor: Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- NHS. "X-ray." nhs.uk. Accessed 2024.
- Royal College of Radiologists. iRefer: Making the Best Use of Clinical Radiology. RCR guidelines for imaging referral.
- Deschênes S, Charron G, Beaudoin G, et al. "Diagnostic imaging of spinal deformities: reducing patients' radiation dose with a new slot-scanning X-ray imager." Spine. 2010;35(9):989-994.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.