Knee Gives Way

A knee that gives way is telling you that something is not holding the joint steady - most often a torn ligament, an unstable kneecap, or a torn meniscus catching inside the joint. It is not something to push through, because each episode of instability can damage the surfaces of the joint further. It is worth having properly assessed rather than waiting to see whether it settles.

Also described as: knee buckling, knee instability, knee collapses, knee feels like it will give out.

Go to A&E now if

•A hot, very painful, swollen knee when you also feel unwell or feverish - this can be an infected joint and is treated as an emergency
•A leg that is cold, pale, numb or that you cannot feel properly below the knee
•An obvious deformity after an injury, or a knee that gives way completely and cannot take any weight at all

What causes it

Anterior cruciate ligament (ACL) tear

The most common reason a knee gives way in sport. People often describe a pop at the time of injury and a knee that swelled quickly, then a joint that feels untrustworthy when turning, pivoting or changing direction.

Kneecap (patella) instability

Here it is the kneecap rather than the whole knee that shifts, often sideways, and often when twisting on a planted foot. It can follow a first dislocation, or happen repeatedly in knees that are simply built loose.

More on patella instability and MPFL reconstruction

Meniscal tear

A torn flap of meniscus can catch between the surfaces of the joint and make the knee momentarily let go, usually with pain along the joint line rather than a sense of the whole knee shifting.

Medial collateral ligament (MCL) injury

Gives way towards the inside of the knee, typically after a blow to the outside of the joint or a twist with the foot planted.

Posterolateral corner (PLC) injury

Instability towards the outside of the knee, and often missed. It matters, because an unrecognised PLC injury is a common reason a later ACL reconstruction fails.

Arthritis and muscle weakness

Not all giving way is a torn ligament. A painful, arthritic knee with weak quadriceps can buckle simply because the muscle gives out - which is why assessment looks at the whole limb, not only the ligaments.

Worth being seen within a week if

•A knee that gave way at the time of an injury and swelled within a few hours
•Repeated episodes of the knee or the kneecap shifting
•A first-time kneecap dislocation
•Giving way after a previous ligament reconstruction

How it is assessed

•A history of how and when it happens - pivoting, stairs, uneven ground - which narrows the cause considerably before anything is examined.
•Examination of the ligaments and the kneecap, comparing the injured knee against the other side.
•Weight-bearing X-rays where alignment or arthritis may be part of the picture.
•MRI where a ligament or meniscal tear is suspected, usually arranged within a week.

Mr Sam Nahas is a consultant knee surgeon in Reading, and sees new knee problems within a week at Circle Reading Hospital. No GP referral is needed for self-pay patients.

Book a consultation

Other knee symptoms

This page is general information about knee symptoms and does not replace individual medical advice. If you are worried about your knee, please be assessed.