Giving Way

For Medical Students

What It Tests

Giving way is the knee failing to support the patient. It is the most common way instability is reported and it has several mechanisms.

Asking about it tests which mechanism: a joint surface shifting, the extensor mechanism failing, the patella subluxing, or pain inhibiting the muscle.

4.2.2 covers instability as a whole. This page is about the episode itself and what its details reveal.

How It Is Performed

Ask for one specific episode in detail rather than a general account.

Ask what they were doing: turning, stepping down, running in a straight line, or standing still.

Ask which way the knee went, accepting that many patients cannot say and that a guess is worse than an admission.

Ask whether they fell, whether the knee swelled afterwards, and how long it took to settle.

Ask whether they expected it, because a knee that gives way without warning is a different problem from one that fails during a movement the patient knew was risky.

What a Positive Means

Giving way while turning or pivoting points to rotational instability and therefore to the cruciate or the lateral structures. 4.14.3 covers the pattern.

Giving way while stepping down stairs or a slope points to the extensor mechanism or the posterior cruciate. 4.11.6 covers chronic posterior deficiency.

Giving way with the kneecap moving, usually with the knee bending under load, points to patellar instability. 4.15.3 covers it.

Giving way in a degenerate knee, without a clear direction and with pain, is usually pain inhibition rather than structural failure. 4.18.6 covers functional limitation.

Swelling after the episode suggests a structural event rather than a muscular one.

MRCS Level

What a Positive Means

The reasoning expected is from the activity to the loaded structure.

A pivot loads the anterior cruciate and the anterolateral structures, so giving way on a pivot implicates them.

A step down loads the quadriceps eccentrically and the posterior cruciate, so giving way there implicates those.

A flexed, loaded, rotating knee loads the patellofemoral joint, so giving way with a sensation at the front implicates the patella.

Standing still loads almost nothing, so giving way while standing is rarely structural and points to pain, to a neurological cause, or to something other than the knee.

How Good It Is

A clear mechanical episode during a defined activity is strong information and performs better than any laxity measurement for whether the knee is functionally unstable.

The patient's report of direction is the weak part. People are poor at describing which way a joint moved during a frightening event, and a confident wrong answer is worse than no answer.

So the activity is reliable and the direction is not, which means the history selects the structures to test and the examination decides between them. 4.14.5 covers the patterns.

The aftermath is reliable: swelling, inability to continue, and time to settle are all well recalled and all informative.

FRCS Level

How Good It Is

At decision level the value of this question is that it identifies the instability a patient actually experiences, which is what an operation is for.

A knee that gives way during work, or during an activity the patient cannot reasonably give up, is a stronger indication than any grade of laxity.

A knee that gives way only during a sport the patient has already stopped is a weaker one, and the conversation is about whether they intend to return.

Episodes that are becoming more frequent, or occurring during less demanding activities, indicate a knee that is deteriorating, and that trajectory matters more than the current frequency.

An episode with swelling in a knee already known to be cruciate deficient usually means a new meniscal or cartilage injury rather than simply another episode.

Where It Misleads

The commonest error is treating all giving way as ligamentous.

Pain inhibition in a degenerate knee produces convincing buckling and does not respond to stabilisation, and this is the single most common misattribution in elective practice.

Quadriceps weakness produces the same complaint and responds to rehabilitation, which is why a wasted thigh changes the interpretation of the history. 4.3.9 covers muscle wasting.

A neurological cause is rare and catastrophic to miss, and a patient who gives way without warning in several directions deserves a neurological examination.

And the patient who has stopped giving way because they have stopped moving is the under-reporting trap this chapter returns to repeatedly. Ask what they no longer do.

Fellowship Level

Where It Misleads

Giving way after a reconstruction is a referral where the history does most of the work, and 4.2.2's four causes apply directly: graft failure, an unaddressed rotational component, quadriceps deficit, and a patellofemoral cause.

The distinguishing question is whether the episode resembles the original symptom. A returned original symptom after a defined event suggests graft failure. A new symptom during pivoting suggests the rotational component was never addressed.

In a multiligament knee the complaint is usually not giving way at all but a knee the patient cannot trust in any direction, and that account is more informative than any attempt to identify a plane. 4.23.6 covers the assessment.

In a hypermobile patient the account has to be weighed against a baseline that was never normal, and the useful comparison is with their own other knee and their own past function. 4.23.3 covers it.

Every discriminating claim here is standard teaching with no figure attached, under decision 023.