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Knee Joint Dissection Guide

Detailed guide to dissecting the knee joint, including the capsule, ligaments, menisci, and associated structures. Understanding knee anatomy is critical for interpreting common sports injuries and surgical procedures.

Learning Objectives

  • ✓Open and examine the knee joint capsule
  • ✓Identify the cruciate and collateral ligaments
  • ✓Examine the medial and lateral menisci
  • ✓Understand the popliteal fossa and its contents
  • ✓Correlate anatomy with common knee injuries

Prerequisites

  • • Completed thigh dissection
  • • Understanding of lower limb innervation
  • • Knowledge of knee movements and mechanics
  • • Familiarity with knee imaging (MRI, X-ray)

Equipment Needed

  • • Scalpel with #22 blade
  • • Dissecting scissors
  • • Forceps
  • • Probe
  • • Bone saw (if removing patella)
  • • Retractors

Dissection Steps

Step 1:Surface Examination

Examine the knee externally. Identify the patella, patellar tendon, tibial tuberosity, femoral condyles, joint line, and head of fibula. Palpate the collateral ligaments on either side.

Key Structures

PatellaPatellar tendonTibial tuberosityMedial femoral condyleLateral femoral condyleJoint lineFibular head
Tip:The joint line is palpable between the femoral condyles and tibial plateaus. It's where the menisci are located and where many joint line tenderness tests are performed.

Step 2:Dissect the Popliteal Fossa

Position the knee face down. Define the boundaries of the popliteal fossa: superolateral (biceps femoris), superomedial (semimembranosus, semitendinosus), inferolateral and inferomedial (gastrocnemius heads). Identify the contents.

Key Structures

Popliteal arteryPopliteal veinTibial nerveCommon peroneal nerveSmall saphenous veinPopliteal lymph nodes
Tip:From superficial to deep: tibial nerve, popliteal vein, popliteal artery ("navy from the back"). The common peroneal nerve runs along the biceps femoris tendon to the fibular neck.

Step 3:Open the Joint Capsule

Flex the knee and make a transverse incision through the patellar tendon. Reflect the patella superiorly (or remove it if necessary). This exposes the intercondylar notch and the interior of the joint.

Key Structures

Joint capsuleSynovial membraneSuprapatellar bursaInfrapatellar fat pad (Hoffa's fat pad)Articular cartilage
Tip:The suprapatellar bursa communicates with the knee joint and extends approximately 3 finger-breadths above the patella. Fluid here indicates joint effusion.

Step 4:Identify the Cruciate Ligaments

Locate the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) within the intercondylar notch. Note their attachments and that they cross each other.

Key Structures

Anterior cruciate ligament (ACL)Posterior cruciate ligament (PCL)Intercondylar notchIntercondylar eminence
Tip:ACL: anterior tibia to posterior lateral femoral condyle (prevents anterior tibial translation). PCL: posterior tibia to anterior medial femoral condyle (prevents posterior tibial translation). They are named by their tibial attachments.

Step 5:Examine the Menisci

Identify the medial and lateral menisci, C-shaped fibrocartilage structures on the tibial plateaus. Note the attachments of the menisci to the joint capsule and the transverse ligament connecting them anteriorly.

Key Structures

Medial meniscusLateral meniscusCoronary ligaments (meniscotibial)Transverse ligamentMeniscofemoral ligaments
Tip:The medial meniscus is C-shaped and firmly attached to the capsule and MCL, making it more prone to injury. The lateral meniscus is more O-shaped and mobile.

Step 6:Identify the Collateral Ligaments

Locate the medial (tibial) collateral ligament (MCL) on the medial side, running from the medial femoral epicondyle to the medial tibia. Find the lateral (fibular) collateral ligament (LCL) from the lateral femoral epicondyle to the fibular head.

Key Structures

Medial collateral ligament (MCL)Lateral collateral ligament (LCL)Deep fibers of MCL (attached to medial meniscus)Popliteus tendon
Tip:The MCL has deep fibers attached to the medial meniscus - this is why MCL and medial meniscus injuries often occur together. The LCL is separate from the lateral meniscus.

Step 7:Examine the Posterolateral Corner

Identify the structures of the posterolateral corner: LCL, popliteus tendon, biceps femoris tendon, and the arcuate ligament complex. These structures are important for rotational stability.

Key Structures

LCLPopliteus tendonBiceps femoris tendonCommon peroneal nerveArcuate ligament
Tip:The posterolateral corner is often injured with ACL tears. The common peroneal nerve is vulnerable here as it wraps around the fibular neck.

Step 8:Examine Articulating Surfaces

Examine the articular surfaces of the femoral condyles, tibial plateaus, and posterior surface of the patella. Note the smooth hyaline cartilage and any areas of damage or wear.

Key Structures

Femoral condyles (articular surfaces)Tibial plateausPatellar articular surface (medial and lateral facets)Trochlear groove
Tip:The patella articulates with the femoral trochlear groove. The lateral patellar facet is larger. Abnormal tracking can cause patellofemoral pain syndrome.

Clinical Correlations

  • •ACL tear: common in pivoting sports, positive Lachman and anterior drawer tests, often requires surgical reconstruction
  • •Unhappy triad: ACL + MCL + medial meniscus tear from valgus force with external rotation
  • •Meniscal tear: locking, clicking, joint line tenderness, positive McMurray test
  • •PCL tear: dashboard injury (knee hits dashboard), positive posterior drawer test
  • •Patellar dislocation: usually lateral, associated with patella alta and trochlear dysplasia

Common Mistakes to Avoid

  • ✗Confusing ACL and PCL (remember tibial attachments: ACL = anterior, PCL = posterior)
  • ✗Not recognizing the attachment of MCL to medial meniscus
  • ✗Damaging the common peroneal nerve during posterolateral dissection
  • ✗Missing the posterolateral corner structures

Study Questions

  1. How do the ACL and PCL work together to stabilize the knee?
  2. Why is the medial meniscus more commonly injured than the lateral meniscus?
  3. What is the mechanism of an "unhappy triad" injury?
  4. How would you test for ACL integrity clinically?
  5. What structures pass through the popliteal fossa and in what order?

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FAQs

Common questions about this dissection

Both test ACL integrity. Lachman test is done at 20-30° flexion (more sensitive, less hamstring guarding). Anterior drawer test is done at 90° flexion. Both assess anterior tibial translation relative to the femur.

The ACL has poor healing capacity due to its intra-articular location and limited blood supply. Autografts (hamstring tendons, patellar tendon) or allografts are used to replace the torn ligament and restore stability.

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