Femoral Footprint

For Medical Students

Structure and Location

The femoral footprint is on the medial surface of the lateral femoral condyle, inside the intercondylar notch. It sits on the posterior part of that wall, close to the articular margin.

It is an oval rather than a circle, with its long axis running roughly from anterosuperior to posteroinferior when the knee is extended. Conventional teaching gives it as of the order of 17 mm long and 9 mm across.

Two bony ridges locate it. The lateral intercondylar ridge, sometimes called the resident's ridge, runs along the wall and marks the anterior limit of the footprint. The bifurcate ridge runs across it and separates the anteromedial from the posterolateral bundle attachment.

Nothing attaches in front of the lateral intercondylar ridge. That is the single most useful fact on this page.

Relations

Above and in front: the lateral intercondylar ridge, then bare wall up to the notch roof.

Behind and below: the articular margin of the lateral condyle and the posterior opening of the notch.

Across the notch: the posterior cruciate's femoral attachment on the medial wall.

The middle genicular artery reaches the footprint from behind.

Function

The footprint position determines how the ligament's length changes through the range. A fibre attached higher on the wall behaves differently from one attached lower.

That is why footprint position matters at all: it is not about the strength of the attachment but about the length pattern it produces.

Clinical Relevance

Graft placement on this footprint is the most studied decision in knee surgery. A graft placed in front of the lateral intercondylar ridge is non anatomical by definition, because nothing native attaches there.

A graft placed too anteriorly is tight in flexion and limits it. One placed too vertically fails to control rotation. Both are placement errors with distinct consequences.

Tunnel drilling technique belongs to 7.20. This page is where the footprint is.

MRCS Level

Structure and Location

Describe the wall first and the footprint second. The lateral wall of the notch is flat to slightly concave and faces medially. Running along it, roughly parallel to the long axis of the femur in extension, is the lateral intercondylar ridge. Perpendicular to it, crossing the footprint, is the bifurcate ridge.

The footprint lies posterior and inferior to the lateral intercondylar ridge, immediately adjacent to the articular cartilage margin posteriorly. The anteromedial bundle attaches proximal to the bifurcate ridge and the posterolateral bundle distal to it, with the knee in extension.

Both ridges are variably prominent and the bifurcate ridge is the less consistent of the two. Absence of a visible ridge does not relocate the footprint.

The fibres fan as they approach the bone, so the footprint is larger than the mid substance cross section.

Relations

The articular margin is the posterior and inferior limit. A tunnel placed too close to it risks a posterior wall blowout.

The notch roof is above, and a tunnel placed too anteriorly directs a graft against it.

The lateral condyle's outer surface is where a tunnel exits, so the condyle's width and the position of the lateral structures constrain the trajectory. 2.1.4 covers the lateral structures.

The distal femoral physis in a skeletally immature knee lies close to the footprint, which is the paediatric constraint.

Blood Supply and Innervation

The footprint and the adjacent ligament are supplied by the middle genicular artery, and the bone of the lateral wall by the lateral genicular arteries through the capsule.

The footprint region is better vascularised than the mid substance, which is relevant to proximal tear healing and to tunnel healing.

Mechanoreceptor density is high near this insertion, which is one of the arguments for preserving a femoral remnant.

Function

Fibre length pattern through range depends on where on the wall a fibre attaches. Proximal attachments lengthen with flexion and distal ones shorten, which is the basis of the bundle description.

A single graft cannot reproduce the whole pattern. It reproduces the behaviour of the part of the footprint it occupies, which is why the position argument exists at all.

3.7 owns the quantitative length change data and 3.7.5 and 3.7.6 own the bundles.

Clinical Relevance

Identify the lateral intercondylar ridge at arthroscopy and work behind it. Where soft tissue obscures the wall, clearing to bone to find the ridge is part of the operation rather than a refinement.

Anterior placement produces a graft that is tight in flexion, limits flexion and is at risk of failure. Vertical placement produces a graft that controls translation and not rotation. Both are described by where the tunnel sits relative to the native footprint.

Posterior wall integrity limits how posteriorly a tunnel can go, and assessing it before drilling is a standard step.

The footprint dimensions on this page are standard teaching values, registered and unchecked. Published footprint measurements differ with method and with how the ligament was removed.

FRCS Level

Relations

In revision the native footprint may be gone and the ridges destroyed. What survives is the articular margin and the overall geometry of the wall, and planning from those is the fallback.

The relation between an existing tunnel and the intended one decides whether a revision is one or two stage. That is geometry, measurable before the operation on computed tomography.

Function

The anatomical placement argument is a mechanical argument about length patterns, not an aesthetic one. A graft placed off the footprint is tight somewhere in the range, and the knee loses either that part of the range or the graft.

Whether single bundle anatomic, double bundle or an added lateral procedure best reproduces native behaviour is an evidence question owned by Section 7. The anatomy on this page says only that no single structure reproduces the whole footprint.

Clinical Relevance

Assess tunnel position on postoperative imaging when a reconstruction has failed, because placement is the commonest technical cause and it is measurable.

In revision, plan from computed tomography. Tunnel overlap, divergence and bone quality decide the staging, and deciding at arthroscopy is deciding late.

In the skeletally immature knee the footprint's proximity to the physis is the constraint, and Section 10 owns the technique choice.

Every published description of this footprint is a set of measurements, and the measurements disagree between authors. The two on this page are conventional teaching and are registered as unchecked; a reviewer should add the rest with sources.

Fellowship Level

Clinical Relevance

Four situations where the femoral footprint is the operation.

The failed reconstruction with an anterior tunnel. The commonest technical failure, and the question is whether a new tunnel can be placed on the native footprint without communicating with the old one. Where it can, one stage. Where it cannot, bone graft first. That decision is made on computed tomography and not at arthroscopy.

The vertical graft that controls translation and not rotation. Revising it means moving the femoral attachment posteriorly and distally on the wall, into a position the original tunnel may have compromised, and the added lateral procedure debate sits here.

The notch with no identifiable ridge. Either previous surgery or an unusually smooth wall. The fallback references are the articular margin posteriorly and the overall anteroposterior extent of the wall, and the honest position is that placement is less certain.

The skeletally immature knee. The footprint sits close to the distal femoral physis, and the choice between physeal sparing and transphyseal technique is a choice about this relation. Section 10 owns it.

In all four the footprint has not moved. What changes is how much of the wall is left to find it on.