Glossary

Arthrogram

Quick answer

An arthrogram is a scan, usually MRI or CT, taken after contrast dye is injected into the knee joint. The dye fills the joint and seeps into tears, outlining them clearly. It is mainly used after previous meniscus or cartilage surgery, when a standard MRI is hard to read, explains Doha knee surgeon Dr. Pablo Gelber at Aman Hospital.

What to expect

The skin is cleaned and numbed with local anaesthetic. Using X-ray or ultrasound guidance, a radiologist passes a fine needle into the joint and injects the contrast. Most people feel a sting from the anaesthetic and then a sense of fullness or pressure in the knee as it fills. You then go straight to the MRI or CT scanner.

The knee may feel tight or achy for a day or two. Infection and allergic reactions are uncommon but are discussed before the procedure.

What it tells the surgeon

After a meniscus repair or partial removal, scar tissue can look bright on a normal MRI and mimic a new tear. With an arthrogram, contrast entering the meniscus is a stronger sign of a true re-tear. The same applies to checking whether a cartilage repair has healed or whether a loose fragment is unstable, for example in osteochondritis dissecans.

A CT arthrogram is an option for people who cannot have MRI, for instance those with some implants.

Frequently asked questions

Why can't I just have a normal MRI?

For most knees a normal MRI is enough. An arthrogram is used when previous surgery or an unclear result makes standard images hard to interpret.

Is the injection painful?

Most people find it uncomfortable rather than painful. Local anaesthetic numbs the skin, and the pressure from the contrast usually fades within a day or two.