I heard a loud pop in my knee and now it hurts. What should I do?

Why this pop is different

Everyday clicks are painless and repeat. A single loud pop at the moment of a twist, landing or collision, followed by pain, is a different thing. It usually means a structure has torn or shifted. How quickly the knee swells is an important clue: swelling within the first few hours often means bleeding inside the joint, which is typical of a torn ligament, a kneecap dislocation or a fracture.

Likely causes

• ACL tear: a pop when changing direction or landing in football, padel or basketball, fast swelling and a feeling the knee is loose
• Meniscus tear: a pop or tearing feeling when twisting on a bent knee, pain on one side and sometimes catching
• Kneecap dislocation: the kneecap shifts to the outside and may pop back, with pain at the inner edge of the kneecap
• MCL sprain: a pop with pain on the inner side after a blow to the outside of the knee
• Tendon rupture: in older adults a pop with sudden inability to straighten the leg against gravity

What to do in the first 48 hours

• Stop playing and do not try to test the knee by running on it
• Ice for 15 to 20 minutes every few hours, with a cloth between ice and skin
• Keep the leg raised above heart level when resting
• Use crutches if walking is painful or the knee feels unstable
• A simple compression bandage can help with swelling
• Take simple pain relief if suitable for you

When to go urgently, and when to book

Go to an emergency department the same day if you cannot put weight on the leg, the knee is locked and will not straighten, the kneecap is still out of place, the leg looks deformed, or the foot is cold, numb or pale.

Otherwise, book to see a knee surgeon within a week. Early examination, before the swelling makes the knee hard to assess fully, helps plan treatment. At Aman Hospital in Doha, Dr. Gelber tests the ligaments, meniscus and kneecap, and an MRI is often arranged after this kind of injury.