Surgical Anatomy

For Medical Students

Structure and Location

Patellofemoral surgery uses three groups of landmarks: the medial femoral prominences, the patella itself, and the tibial tubercle.

The medial femoral prominences are the adductor tubercle and the medial epicondyle, the same two 2.9.7 describes. The medial patellofemoral ligament attaches between them.

The patella's medial border carries the ligament's broad attachment over its upper third to half.

The tibial tubercle is the distal landmark, where the patellar tendon attaches and where a realignment procedure works. 2.2.5 covers it.

The trochlea is the fourth landmark and it is cartilage rather than bone, which makes it harder to use. 2.12.1 covers it.

Relations

The infrapatellar branch of the saphenous nerve crosses every anterior and medial approach to this joint.

The medial collateral ligament's femoral attachment lies close to the patellofemoral ligament's, which 2.9.7 covers.

The genicular arteries run in both retinacula, so a release on either side divides vessels. 2.12.4 covers them.

The suprapatellar pouch lies deep to the quadriceps tendon above the patella.

Function

Almost every error in this field is a femoral error. The ligament's length behaviour through flexion is set at the femur, and a few millimetres changes it.

The patella is small and sometimes fragile, so what is done to it is constrained by the bone rather than by the ligament.

Operative technique is Section 7, chapters 7.51 to 7.57. This page covers what is where.

Clinical Relevance

The femoral point is confirmed on imaging rather than by feel, because the landmarks are close together and the consequence of error is large.

Patellar fixation competes with patellar strength, especially in a small or previously drilled patella.

The saphenous nerve branch crossing the field means numbness is the commonest minor complication of this surgery.

MRCS Level

Structure and Location

Learn the femoral point as a set of offsets, as on the medial side. Conventional teaching places it about 10 mm distal and 1 mm anterior to the adductor tubercle, and about 5 mm proximal and posterior to the medial epicondyle.

On a true lateral radiograph the point lies just anterior to the posterior cortical line, between the posterior origin of the medial condyle and the level of the posterior point of Blumensaat's line. That is the radiographic description, and it is the one used at operation.

On the patella, the attachment spans the upper third to half of the medial border. Conventional teaching gives a width of about 20 mm.

The tibial tubercle's position relative to the trochlear groove is the measurement a distal realignment addresses, and 5.12 owns its imaging.

Relations

The three medial femoral structures, the collateral ligament, the patellofemoral ligament and the adductor magnus tendon, lie within about 15 mm of each other.

The infrapatellar branch of the saphenous nerve runs transversely across the medial field, as 2.9.7 describes.

The lateral retinaculum carries the lateral genicular vessels, so a lateral procedure has a vascular cost. 2.12.4 covers it.

The patella's blood supply enters mainly at its inferior pole and from the anastomosis around it, so anterior and lateral surgery together can compromise it.

Blood Supply and Innervation

The patella is supplied by the genicular anastomosis, with the main contribution entering at the inferior pole through the fat pad.

A lateral release divides part of that anastomosis, and a tubercle osteotomy can affect the inferior pole supply, so the two together are a greater insult than either alone.

Nerve supply to the anterior knee is diffuse, from medial and lateral articular branches, which is why anterior knee pain is poorly localised.

Function

Femoral position sets the graft's length behaviour: too proximal and it tightens in flexion, too distal and it slackens. 3.12.5 covers the mechanics.

Patellar fixation sets the load distribution across a small bone, so the number and size of tunnels is a strength question.

Tubercle position sets the direction of the extensor pull, so a distal procedure changes the vector that the proximal soft tissue has to resist.

Clinical Relevance

Confirm the femoral point on a true lateral image before fixing anything.

Count the holes in the patella across all operations a patient has had, since each one reduces the bone's strength.

Consider patellar vascularity before combining a lateral release with anterior or distal surgery.

Protect the infrapatellar branch, and warn the patient about numbness in advance rather than afterwards.

FRCS Level

Relations

The femoral field is the crowded one, as it is medially and laterally. Three attachments within 15 mm, and a radiographic method exists because palpation is not accurate enough.

The patella is the fragile one. Its size, its supply at the inferior pole and its history of previous tunnels together set what can be done at the anterior end.

The tubercle is the one that changes everything else. Moving it changes the vector the soft tissue resists, so a proximal and a distal procedure are not independent.

Function

Treat femoral accuracy as the single most consequential variable. Every other error here is recoverable and this one is not, because it changes the construct's behaviour through the whole range.

Combination procedures compound their vascular cost. Lateral release, anterior work and tubercle osteotomy each take part of the anastomosis, and the patella has one supply.

Soft tissue cannot correct bone, which 2.12.2 states for the ligament and which applies to every soft tissue procedure in this chapter.

Clinical Relevance

Image the femoral point intraoperatively rather than relying on anatomy by feel.

Plan the whole construct before starting, since proximal and distal procedures interact through the extensor vector.

Assess previous surgery for holes in the patella and for lateral release, and weigh the vascular cost before adding to either.

Avoid combining a lateral release with distal realignment without a reason, because the patella's supply is the thing being spent.

Fellowship Level

Clinical Relevance

The femoral point is the whole operation. Radiographic confirmation exists because a point identified by palpation is wrong often enough to matter, and the error is not visible at the time: a graft fixed too proximally feels correct in extension and binds in flexion, which the patient discovers weeks later. Checking takes one image.

Patellar fracture is a bone complication wearing a ligament's name. A small, osteopenic or previously drilled patella is the risk factor, and the anatomy offers an alternative in the quadriceps tendon attachment that 2.12.3 describes. That choice is made before the incision rather than at the moment the drill is picked up.

Vascular arithmetic is rarely done. The patella has one anastomosis; lateral release takes part of it, a tubercle osteotomy threatens the inferior pole supply, and anterior work takes more. Each is defensible alone and the combination is what produces an avascular patella, which 6.63 covers.

The soft tissue cannot fix the bone, and this is the point at which that has to be said rather than implied. A trochlea that does not guide, a tubercle too far lateral or a patella too high is a bony problem, and a 1 mm sheet reconstructed perfectly will fail against it. 5.12 holds the measurements that decide which problem a patient has.

Revision is where the anatomy has already been spent. Previous tunnels, a divided lateral retinaculum, an altered tubercle and scar across the medial field together mean the landmarks that remain are the adductor tubercle and the epicondyle. Plan from those, and 7.57 carries the rest.

Over-constraint presents as pain rather than as stiffness. A construct tensioned to hold the patella loads the medial facet through every degree of flexion, and the patient reports anterior knee pain in a knee that no longer dislocates. That is a successful operation by one measure and a failure by the one that matters.