ACL basics
Describe the common forces/ mechanisms of ACL injury
valgus collapse, internal rotation of the femur, and external rotation of the tibia.
Plant and pivot, hyperextension or direct blow
When would you consider conservative management? List 3
Older age
Partial tears and no instability symptoms
Complete tears and no symptoms of knee
instability during low-demand sports, willing to
give up high-demand sports
Name 3 risks for re-rupture
Altered landing mechanics (frontal and sagittal
plane knee moments, postural stability deficit)
Decreased hamstring strength
Younger athletes
Female
Name 2 mechanisms of PCL rupture
1. Direct Blunt Trauma to the Front of the Knee (Dashboard Injury)
2. Hyperflexion of the Knee
3. Rotational Forces (with Knee Flexion)
What is a segond fracture?
A small avulsion fracture of the lateral tibial plateau, where the lateral capsular ligament pulls off a piece of bone.
Describe 3 commonly performed tests for ACL insufficiency
1. Lachman Test
Most sensitive for acute ACL tears.
Method: With the patient supine and the knee flexed to ~20–30°, the examiner stabilizes the femur with one hand and pulls the tibia anteriorly with the other.
Positive sign: Increased anterior translation of the tibia with a soft or absent endpoint.
2. Anterior Drawer Test
Method: Patient lies supine with the knee flexed to 90°. The examiner pulls the tibia forward while stabilizing the foot.
Positive sign: Excessive anterior movement of the tibia compared to the uninjured side.
Less sensitive than the Lachman test, especially in acute injuries due to hamstring guarding.
3. Pivot Shift Test
Best for chronic ACL deficiency, but harder to perform on acute injuries.
Method: With the patient supine, the examiner applies valgus and internal rotation forces to the knee while moving it from extension to flexion.
Positive sign: A palpable or visible "clunk" as the tibia reduces from a subluxed position.
Describe the 3 common causes of ACL reconstruction failure
1. Technical Error (most common)
Examples:
Incorrect tunnel placement (especially femoral tunnel) → leads to graft impingement or improper tensioning.
Improper graft tension or fixation.
Impact: Poor knee biomechanics, persistent instability, or graft rupture.
2. Biologic Failure (poor graft incorporation or healing)
Causes:
Inadequate graft revascularization or incorporation into the bone tunnels.
Early aggressive rehab stressing an immature graft.
Patient factors: smoking, poor nutrition, comorbidities.
Result: Graft stretches out or doesn't integrate, leading to laxity.
3. Traumatic Re-injury
Factors:
Incomplete rehabilitation or premature return to play.
Underlying neuromuscular deficits (e.g. poor landing mechanics).
Describe a grading system used to quantify PCL injury
Grad I: Mild, no translation, Stable, minimal pain
II: Moderate, Translation <1cm, some instability
III: Complete rupture, >1cm translation, Significant instability
Where are bone bruises most commonly seen following ACL injury?
Lateral femoral condyle and posterolateral tibial plateau.
What 3 factors indicate when reconstruction surgery could proceed?
Minimal or no effusion (swelling),
Near full range of motion (especially full extension),
Controlled pain and inflammation.
Visible return of quad tone and activation
Give 4 examples of common technical errors in ACL reconstruction?
1. Incorrect Tunnel Placement
2. Improper Graft Tensioning
3. Inadequate Fixation of the Graft
4. Notch Impingement
5. Incorrect Graft Selection or Sizing
6. Failure to Address Concomitant Pathologies
What is the generally recommended treatment for grade 1-3?
1: Conservative
2: Usually conservative
3: Surgical in active patients
What are 3 commonly described associated injuries?
MCL tear
Meniscus tear- medial more common
Segond fracture
Discuss pros/cons of the 3 main graft options
Graft TypeBenefitsDrawbacks
BPTB
Pros: Strong fixation, low failure rate
Cons: Anterior knee pain, patellar complications
Hamstring
Pro: Less knee pain, cosmetic incision
Con: Hamstring weakness, slower healing
Quadriceps
Pro: Strong graft, low knee pain
Cons: Less data, potential quad weakness
Preoperative imaging should be assessed for what 3 major issues prior to ACL revision reconstruction?
Tunnel position and size: Ensure proper placement of new tunnels.
Bone quality: Assess for sufficient bone stock and potential bone loss.
Associated injuries: Evaluate for meniscal, cartilage, or other ligament injuries that could impact the outcome of ACL revision surgery.
What other associated injuries should we also keep in mind and examine for in a pcl rupture? List 5
Ligament injuries: ACL, MCL, LCL, PLC injuries.
Meniscal tears: Common, particularly the medial meniscus.
Chondral damage: Articular cartilage damage or tibial plateau fractures.
Bone contusions: Femoral or tibial condyle bruising.
Fractures: Tibial spine, tibial plateau, femoral fractures.
Vascular/nerve injuries: Popliteal artery or peroneal nerve injury.
Instability: Posterior laxity and chronic knee instability.
Why are ACL injuries more common in
women? (List 4 Reasons)
Neuromuscular forces and control (more quads
dominant)
Landing biomechanics (land in more extension)
Leg dominance
Valgus Leg Alignment (pelvic width, Q-angle)
Smaller notches
Collagen production genetic factors
Smaller Ligaments
Ligament laxity
Hormone levels
How does the presence of medial-sided OA and varus malalignment affect treatment options for an ACL deficient patient with knee instability and pain? List 3 considerations
ACL Reconstruction Alone May Be Inadequate
HTO shifts the load from the damaged medial compartment to the healthier lateral side by correcting varus alignment.
Consider TKA if older
Worsen Biomechanics
Varus alignment shifts load toward the medial compartment, accelerating medial OA progression.
In an ACL-deficient knee, varus deformity increases instability, particularly during activities requiring pivoting or deceleration.
Young/active: Consider HTO ± ACL reconstruction.
Older/advanced OA: Likely candidates for TKA.
Discuss 3 errors in tunnel placement and why they are bad.
Femoral Tunnel Too Anterior or Vertical:
Leads to limited rotational control and graft impingement in extension.
Tibial Tunnel Too Anterior:
Causes graft impingement on the intercondylar notch → pain, restricted motion, or graft failure.
Non-anatomic Tunnel Position:
Fails to replicate natural ACL mechanics → persistent instability.
Describe a posterior approach to the knee
1. Patient Position: prone with tourniquet, knee slight flexion
2. Skin Incision
A longitudinal S-shaped over the popliteal fossa
3. Superficial Dissection
The small saphenous vein and medial sural cutaneous nerve are identified and protected.
The fascia overlying the popliteal fossa is incised vertically.
4. Deep Dissection
The tibial nerve, common peroneal nerve, and popliteal artery and vein are carefully identified and retracted.
Careful dissection between the medial and lateral heads of the gastrocnemius allows deeper access.
If needed, the medial head of gastrocnemius can be partially elevated to improve exposure.
5. Exposure of Posterior Knee Structures
Once through the posterior capsule:
PCL is accessed centrally.
Posterolateral corner structures (e.g., popliteus tendon, arcuate ligament) are accessed laterally.
If addressing a posterior tibial plateau fracture, retract soft tissues to expose the bone surface.
6. Closure