Do I Need an X-Ray? Clinical Guidelines for Knee and Ankle Injuries

February 8, 2026

Do I Need an X-Ray? Clinical Guidelines for Knee and Ankle Injuries

As a sports performance physical therapist, I often get asked:
“How do I know if my knee or ankle is broken?”
“Do I need an X-ray?”

After an acute injury, it can be difficult to know whether you’re dealing with something that needs medical imaging or something that can be treated conservatively with physical therapy. Fortunately, there are clinical guidelines that help healthcare providers — and patients — make safer decisions about when an X-ray may be necessary.

Two of the most widely used guidelines are the Ottawa Knee Rules and the Ottawa Ankle Rules.

The Ottawa Knee Rules

The Ottawa Knee Rules are a set of criteria used after an acute knee injury with localized pain to help determine whether an X-ray is recommended.

An X-ray may be indicated if any of the following are present:

Age 55 or older
Isolated patellar (kneecap) tenderness
Fibular head tenderness (the bone on the outside just below the knee)
Inability to bend the knee to 90 degrees
Inability to bear weight, defined as taking fewer than four steps immediately after the injury or in a medical setting

If one or more of these signs are present, imaging may be recommended to rule out a fracture.

The Ottawa Ankle Rules

The Ottawa Ankle Rules help determine whether an ankle injury may involve a fracture.

An X-ray may be needed if there is:

Bony tenderness along the posterior edge or tip of the lateral malleolus (outer ankle bone)
Bony tenderness along the posterior edge or tip of the medial malleolus (inner ankle bone)
Inability to bear weight for four steps

The Ottawa Foot Rules

These guidelines also apply to potential foot fractures.

An X-ray may be recommended if there is:

Tenderness at the navicular bone (midfoot)
Tenderness at the base of the fifth metatarsal (outer edge of the foot near the little toe)
Inability to bear weight for four steps

When to Consider Getting an X-Ray

If you’ve recently been injured — for example, during a run, workout, or basketball game — and you notice sharp, localized bone tenderness or difficulty putting weight on the injured area, it may be worth getting evaluated for a possible fracture.

These rules don’t replace a professional evaluation, but they can help guide decision-making and reduce unnecessary imaging while still catching injuries that need medical attention.