Gross Anatomy

For Medical Students

Structure and Location

The distal femur is where a cylindrical shaft becomes a joint surface. Moving distally, the shaft flares into a metaphysis and then into two condyles, which are separated behind by the intercondylar notch and joined in front by the trochlea.

Each condyle carries an epicondyle on its outer surface. The medial epicondyle is the larger of the two and has the adductor tubercle immediately above it. The lateral epicondyle is smaller and flatter. Both are palpable through skin, which makes them the reference points for almost every description that follows.

The articular surface is continuous. It runs from the trochlea anteriorly, over each condyle, and back to the posterior condyles, interrupted only by the notch.

Relations

In front of the distal femur lie the quadriceps tendon and the patella, with the suprapatellar pouch of the synovial cavity extending above the trochlea.

Behind it is the popliteal fossa. The popliteal artery lies closest to the bone, with the vein superficial to it and the tibial nerve most superficial of the three. The common peroneal nerve runs along the lateral border of the fossa toward the fibular neck.

Medially the adductor magnus inserts on the adductor tubercle and the superficial medial collateral ligament arises from the medial epicondyle. Laterally the lateral collateral ligament arises from the lateral epicondyle. The two heads of gastrocnemius arise from the posterior surface above each condyle.

Function

The distal femur is the proximal half of two joints at once. Its condyles articulate with the tibial plateau and its trochlea articulates with the patella.

Its shape, rather than any ligament, sets the path the tibia follows through flexion. The condyles are not circular in profile, and the radius of curvature differs between their anterior and posterior parts, so the contact point shifts as the knee bends.

Clinical Relevance

Almost every surgical reference around the knee is taken from a distal femoral landmark. The epicondyles define the transepicondylar axis, the adductor tubercle locates the medial retinacular attachments, and the notch roof is the landmark used to orient the femoral side of cruciate reconstruction.

The relation worth carrying from this page is the popliteal artery lying directly behind the capsule. Anything that passes from front to back at this level passes toward it.

MRCS Level

Structure and Location

Describe the distal femur as a metaphysis carrying two condyles. The medial condyle projects further distally and is longer front to back; the lateral condyle projects further anteriorly and carries the larger trochlear facet. That asymmetry is the answer to why the femur looks different on each side.

On the lateral condyle, outside the joint, lies the popliteal sulcus, where popliteus arises. Its relation to the lateral collateral origin is a standard viva question: the collateral arises proximal and posterior to the popliteus origin.

Relations

Anterior: quadriceps tendon, patella, suprapatellar pouch.

Posterior: popliteal artery on the bone, then vein, then tibial nerve. The artery is tethered proximally at the adductor hiatus and distally by the fibrous arch of soleus, which is why it tolerates displacement poorly at this level.

Medial: adductor magnus to the adductor tubercle, superficial medial collateral ligament from the medial epicondyle, medial head of gastrocnemius from above the condyle, and the medial patellofemoral ligament running from the region between adductor tubercle and epicondyle.

Lateral: lateral collateral ligament from the lateral epicondyle, popliteus from its sulcus, lateral head of gastrocnemius from above the condyle, and the lateral intermuscular septum along the posterolateral shaft.

Blood Supply and Innervation

The shaft receives a nutrient artery from a perforating branch of the profunda femoris. The metaphysis and epiphysis are supplied from the genicular anastomosis, the arterial network lying on the capsule and under the retinacula.

That anastomosis is fed by the descending genicular artery from the femoral artery, the descending branch of the lateral circumflex femoral, the superior medial and superior lateral genicular arteries, the middle genicular artery which enters the notch, the inferior medial and inferior lateral genicular arteries, and the anterior and posterior tibial recurrent branches from below.

Innervation follows Hilton's law: the nerves supplying the muscles that act on the joint supply the joint itself. Articular branches come from the femoral nerve through the nerves to the vasti, from the obturator nerve, and from the tibial and common peroneal nerves posteriorly.

Function

The distal femur transmits load from the shaft to the tibia across two condyles, and carries the patellofemoral joint on its anterior surface.

Because the medial condyle is longer in the sagittal plane than the lateral, the two do not finish their arc together as the knee extends. That difference is the bony basis of the terminal rotation of extension, which 3.13 takes further.

Clinical Relevance

The transepicondylar axis is the rotational reference for the femoral component in arthroplasty, and the asymmetry of the condyles is why that axis is not parallel to the posterior condylar line. The difference is conventionally taught as about 3 degrees of external rotation.

The notch roof orients the femoral tunnel in cruciate reconstruction; 2.7.6 owns the footprint itself.

Distal femoral fractures threaten the popliteal artery, and the vessel's proximal and distal tethering means a displaced supracondylar fragment can injure it without any penetrating wound. Examination of the foot pulses is part of examining the thigh.

The genicular anastomosis is why the skin and capsule around the knee tolerate incisions in some planes better than others, and why a second incision placed close to a first one risks the tissue between them.

FRCS Level

Relations

The planes that matter at this level are the ones an approach uses. Anteriorly the quadriceps and its retinacula can be entered medially or laterally to the patella, or below the vastus medialis, and each entry trades exposure against the blood supply of the skin flap and the integrity of the extensor mechanism.

Posteriorly there is no safe plane. The popliteal vessels lie on the capsule, and the bone is approached from the side rather than from behind.

The lateral intermuscular septum is the landmark for the lateral approach to the shaft, and the perforating vessels crossing it are the reason that plane bleeds.

Function

Femoral geometry is the fixed element in every alignment decision at the knee. The distal articular surface sits in valgus relative to the anatomical axis of the shaft, conventionally taught as 5 to 7 degrees, and the angle between them varies between people.

That variation is why a single cutting angle does not reproduce the same alignment in every patient, and why the debate about mechanical, anatomical and kinematic alignment is an argument about which femoral reference to trust. Section 7 owns the argument. What belongs here is that the reference points are all bony and all on this page.

Clinical Relevance

Three consequences of distal femoral anatomy recur in decision making.

The condyles are asymmetrical, so rotational references disagree with each other. Choosing between the transepicondylar axis, the posterior condylar line and the anteroposterior axis of the trochlea is choosing which disagreement to accept.

The epiphyseal blood supply arrives through the capsule and the retinacula rather than through the shaft, so wide periosteal stripping of the metaphysis has a cost that a diaphyseal exposure does not.

The notch is a fixed volume containing both cruciates. Anything added inside it, whether graft or bone, competes for that volume.