My knee snaps on the inside when I bend it. Could it be a plica?

What the snap is

A plica is a fold in the knee's lining left over from development. When it becomes thickened and less elastic, it can catch on the rounded end of the thigh bone and flick over it as the knee bends, usually somewhere between a quarter and halfway bent. Many people can feel a tender cord under their fingers just inside the kneecap when they bend and straighten the knee slowly.

The snap is usually soft and repeatable, without the knee getting stuck or giving way.

Clues that point towards a plica, and away

• Towards a plica: an ache at the inner front of the knee, next to the kneecap, with a soft snap
• Towards a plica: worse with cycling, stairs, squats or after sitting with the knee bent
• Towards a plica: little or no swelling, and the knee feels stable
• Away from a plica: pain on the joint line further back, sharp catching or locking, which suggest the meniscus
• Away from a plica: the kneecap slipping or feeling unstable
• Away from a plica: swelling within hours of an injury

What to do now

Ease off the movements that provoke it for two to three weeks: indoor cycling classes, deep squats, lunges and stair training. Keep moving with walking on the flat and swimming with a gentle kick. Ice for 15 to 20 minutes after activity. When sitting at a desk or driving, straighten the knee regularly.

Start gentle quadriceps exercises, such as straight leg raises and short-range squats, plus hamstring and front-thigh stretches. These reduce strain on the front of the knee and are the foundation of treatment.

When to see a knee surgeon

Book an assessment if the snapping and ache last more than a few weeks, keep returning, or stop you training. Seek prompt care if the knee truly locks, swells significantly or gives way. At Aman Hospital in Doha, Dr. Gelber feels for the plica, tests the meniscus and kneecap, and uses MRI mainly to rule out other causes before confirming a plica problem.