Why are posterolateral corner injuries often missed, and how are they diagnosed?

Why they slip through

• A torn ACL or PCL is obvious on MRI and draws attention, while outer-side damage may be reported briefly or not at all
• Pain and swelling make the knee hard to examine in the first days
• The key tests check rotation, which is not part of every quick knee examination
• Isolated outer-side injuries are uncommon, so they are not always suspected

The examination

The surgeon looks at how you stand and walk, watching for the knee bowing outward with each step. With you lying down, the knee is gently stressed outward at full extension and at about 30 degrees of bend. The dial test compares how far each foot rotates outward with the knee bent at 30 and 90 degrees; increased rotation suggests a posterolateral corner injury, and a difference at both angles suggests the PCL is involved too. The nerve function in the foot is always checked.

Imaging

MRI shows the LCL, popliteus tendon, biceps tendon and fibular head, as well as the cruciate ligaments and meniscus. It is most informative in the first weeks after injury, when tears are still clearly visible.

Stress X-rays, taken while a controlled outward force is applied, measure how much the outer joint opens compared with the other knee. They help grade the injury and are useful for planning surgery and confirming the result afterwards. A long-leg standing X-ray may be added in chronic cases to check overall leg alignment.

What this means for you

If you have been told you have an ACL or PCL tear after a high-energy injury, it is worth making sure the outer side has been examined properly. At Aman Hospital in Doha, Dr. Gelber reviews existing scans, repeats the examination and arranges further imaging only where it changes the plan.