A knee arthrogram is an imaging study in which a small amount of contrast dye is injected directly into the knee joint so that the inside of the joint shows up clearly on X-ray. A plain X-ray renders bone well and soft tissue poorly. Filling the joint with contrast outlines the surfaces that a bone-only image leaves invisible, and that is the whole reason the study exists.
At Regenerative Joint Clinics in Riverdale, GA, a knee arthrogram is performed in the office using a fluoroscopic C-arm. Fluoroscopy is live X-ray, so the provider watches the needle and the spreading contrast in real time instead of estimating placement and hoping. The appointment is short. Most of it is preparation and positioning, and the injection itself takes only a few minutes.
What follows is a walk through the five stages of the appointment, what each stage actually feels like, and what the two days afterward involve.
Why a knee arthrogram instead of a plain X-ray?
A standing X-ray is the workhorse of a knee evaluation and it answers a lot on its own. It shows how much space is left between the bones, whether the joint is wearing unevenly, and how the leg lines up under load. For a great many knees that is enough to build a plan around.
What it cannot do is show you the cartilage surface itself, or the soft tissue structures inside the capsule, because none of that absorbs enough radiation to register. Contrast solves that problem mechanically rather than cleverly. Injected into the joint, it seeps into the small spaces between and around those structures and makes their outlines visible by filling in everything they are not.
That is also why joint distension matters. Spreading the capsule slightly with fluid separates surfaces that otherwise sit flat against one another, which is what allows a small irregularity to read as an irregularity instead of disappearing into the tissue beside it.
The 5 stages of a knee arthrogram appointment
Stage 1: The decision and the consent conversation
Nothing is injected until there is a reason to inject it. The visit starts with an exam and a look at whatever imaging already exists, because a study that will not change the plan is a study worth skipping.
If a knee arthrogram is recommended, you will read and sign a consent form. Ours is candid about what it is agreeing to. It lists the risks by name, including pain, bleeding, infection, failure to produce the desired result, and drug reaction ranging from minor to major. It states plainly that no one has given a promise or guarantee about what the result will be. And it records that alternatives were discussed, explicitly including the alternative of doing nothing. That last line is not filler. Choosing to wait is a legitimate option and the form treats it as one.
Stage 2: Positioning and numbing
You will lie down with the knee positioned under the C-arm. The skin is cleaned and draped, and a local anesthetic is used to numb the skin and the tissue along the path the needle will take. Our consent form covers this specifically, since local anesthesia is part of the procedure rather than an optional extra.
People are usually braced for this stage to be the worst of it. It generally is not.
Stage 3: The contrast injection under live X-ray
This is the part that makes a knee arthrogram different from a blind injection. With fluoroscopy running, the provider advances the needle into the joint and injects the contrast while watching the screen. If the contrast flows away from the needle tip and opacifies the joint space, the needle is where it should be. If it pools where it should not, that is visible immediately and can be corrected before anything else happens.
Lungu and Moser described this confirmation step in a practical guide to fluoroscopic arthrography published in Insights into Imaging in 2015, noting that flow of contrast away from the needle tip and opacification of the joint space are what confirm adequate needle position. It is a small detail that carries a lot of weight, because it converts an assumption into an observation.
Stage 4: The images
Once the joint is filled, images are taken with the knee in more than one position. You may be asked to move or bend the knee between shots so the contrast distributes rather than settling in one spot. The knee often feels tight or full at this point, which is expected and temporary.
Stage 5: The two days afterward
Aftercare for a knee arthrogram is not complicated, and our clinic hands out the same written instruction sheet to everyone. Apply an ice pack to the injected area once or twice daily for 10 to 15 minutes, for two days. For the first 24 hours, take it easy: limit sports, strenuous exercise and long periods of standing.
The sheet is also specific about what is normal and what is not. Injection site pain, swelling, warmth or redness, rash, itching or bruising around the joint are the common effects, and they are usually mild and short lived. Over-the-counter pain relievers such as Tylenol, Advil or Aleve are fine, as are topical creams or rubs if those help you. You should keep taking your prescribed medications and supplements as usual.
Three things warrant a phone call rather than waiting: excessive pain, swelling that is not relieved by Tylenol or ice, and any fever or chills. Our number is (470) 895-0610.
How much contrast actually goes into the knee?
Less than most people picture. The knee is a roomy joint. Lungu and Moser put its capacity at more than 40 mL, yet note that diagnostic arthrography is appropriately performed with a volume of 10 to 20 mL. The aim is to coat and separate the joint surfaces, not to inflate the knee.
The shoulder is a useful contrast. Its capacity runs about 8 to 15 mL normally, and the same authors note it can drop below 7 mL in adhesive capsulitis, better known as frozen shoulder. A shoulder that has tightened down simply holds less. Roberts and Escobar, writing in StatPearls, give a typical total injection volume of 10 to 15 mL for the shoulder joint and note that where an MRI is to follow the injection, it should ideally begin within 90 minutes, because contrast is absorbed steadily from the moment it goes in.
How a knee arthrogram differs from an MRI
These get conflated constantly, so it is worth separating them cleanly.
A knee arthrogram is an injection plus X-ray imaging. An MRI of the knee is a scan that uses a magnetic field, involves no injection in its standard form, and no radiation. They answer overlapping but different questions, and an MRI is not automatically the better study simply because it is the more expensive one.
The two are sometimes combined. In an MR arthrogram, contrast is injected into the joint and the MRI follows. That combined study is performed at an imaging center, not in our office. What we perform in Riverdale is the fluoroscopic arthrogram, using the same C-arm we use for image-guided joint injections.
Our in-office imaging stack is digital X-ray, fluoroscopy and diagnostic musculoskeletal ultrasound. If an MRI is the right next step for your knee, it is ordered and performed elsewhere, and the report comes back to us.
What are the risks of a knee arthrogram?
Any procedure that puts a needle into a joint carries some risk, and the honest version is the one printed on our own consent form: pain, bleeding, infection, failure to produce the desired result, and drug reaction from minor to major. Serious complications are uncommon, but uncommon is not the same as impossible, which is why the aftercare sheet names fever, chills and unrelieved swelling as reasons to call.
There is also radiation to account for, since fluoroscopy is X-ray. The exposure from a short guided injection is small, and it buys something concrete in return, namely confirmation that the contrast went where it was supposed to go.
How we use a knee arthrogram at Regenerative Joint Clinics
Our arthrogram consent forms are filed alongside the rest of our injection paperwork, under the heading of serial X-rays and injections, and the condition named on the form is osteoarthritis of the joint. That tells you where this study sits in our practice. It is part of an osteoarthritis workup rather than a standalone test, and it exists to inform what comes next.
Separate forms exist for the right knee, the left knee and both knees together, which reflects how often osteoarthritis is not a one-knee problem. We perform knee arthrograms only; where a shoulder arthrogram is needed, we arrange it elsewhere.
What the study informs is the Targeted Restoration Protocol, our non-surgical program. Depending on what the joint looks like, that plan may combine hyaluronic acid gel injections, platelet-rich plasma, cortisone for short-term relief of an acutely inflamed joint, unloader bracing, physical therapy by referral, and activity and lifestyle changes. Where a joint is holding excess fluid, joint aspiration may come first.
Imaging findings also have to be read against the person in front of you. A knee can look worse on a picture than it feels, and it can feel far worse than it looks. That is a well-recognized problem with meniscal findings in particular, which is why we discuss it at length in our guide to treating a meniscus tear without surgery, and why we grade what we see against symptoms and function rather than in isolation. Our guide to the stages of knee osteoarthritis covers how that grading works.
Frequently asked questions about a knee arthrogram
Does a knee arthrogram hurt?
Most people describe pressure rather than sharp pain. The skin and the tissue along the needle path are numbed with a local anesthetic first, so the part that people expect to hurt is usually the part they feel least. The more common sensation is fullness or tightness in the knee as the contrast fills the joint, and that eases over the following day as the body reabsorbs the fluid.
How long does a knee arthrogram take?
Plan on being at the office longer than the procedure itself. The injection under live X-ray takes only a few minutes. Checking in, reviewing consent, positioning the knee, cleaning the skin and taking the images account for most of the visit.
Is a knee arthrogram the same as an MRI?
No. A knee arthrogram is a contrast injection into the joint, and the pictures are taken with X-ray. An MRI is a separate scan that uses a magnetic field and no radiation. The two are sometimes combined at an imaging center, where contrast is injected first and the MRI follows, but that is a different study from the fluoroscopic arthrogram performed in our Riverdale office.
How much contrast goes into the knee?
Less than the knee can hold. Lungu and Moser, writing in Insights into Imaging in 2015, note that the knee joint capacity is more than 40 mL while diagnostic arthrography is appropriately performed with 10 to 20 mL. The goal is enough contrast to outline the joint surfaces, not to fill the joint to capacity.
What should I do for the two days after a knee arthrogram?
Our written post-injection instructions ask patients to apply an ice pack to the injected area once or twice daily for 10 to 15 minutes for two days, and to take it easy for the first 24 hours by limiting sports, strenuous exercise and long periods of standing. Mild soreness, swelling, warmth or bruising around the joint is common and usually short lived.
When should I call the clinic after a knee arthrogram?
Call us at (470) 895-0610 if you have excessive pain, swelling of the joint or injection site that is not relieved with Tylenol or ice, or any fever or chills. Those three are the specific triggers listed on our post-injection instruction sheet.
Do I need a knee arthrogram before treatment can start?
Not usually. Many knees are evaluated with a physical exam, weight-bearing X-ray and, where it helps, diagnostic ultrasound. A knee arthrogram is ordered when a clearer picture of the joint surfaces would genuinely change the plan, not as a routine step for every patient.
Talk to someone about your knee
If your knee has been evaluated already and you are still not sure what is actually wrong with it, a conversation is a reasonable next step. Whether that conversation ends in a knee arthrogram, a different study, or no imaging at all depends on what the exam turns up.
Regenerative Joint Clinics is at 483 Upper Riverdale Road SW, Suite F, Riverdale, GA 30274. Call (470) 895-0610, email contact@regenerativejointclinics.com, or get in touch through our contact page to schedule an evaluation. Appointments are required; we are not a walk-in clinic.
Medical disclaimer: this article is general education about a knee arthrogram and is not medical advice. It cannot account for your individual history, medications or allergies. Consult a qualified healthcare provider before starting or changing any treatment or diagnostic plan.
