Tibiafemoral Joint, ACL, PCL, MCL, LCL and Meniscus

ACL Anatomy (Bundles)

Anteromedial bundle: taut in flexion. Most often injured in same position

Posterolateral bundle: taut in extension. Most often injured in same position

During examination for possible ACL tear, what do you check?

ACL, MCL, LCL and PCL

Test at multiple angles, at 0-30 deg and 80-90 deg

Post-injury of ACL tear, what structure guards at 90 deg of flexion?

Hamstrings due to helping resist anterior tibia translation

Primary Function of the ACL?

Primary restraint of anterior translation of tibia and IR

Secondary function of the ACL?

Secondary restraint to varus and valgus stresses at the knee

What else does the ACL do?

Guides the screw-home mechanism

Terminal Extension Screw Home

During terminal extension, the lateral femoral condyle finishes rolling/gliding before the medial side → causes tibial ER in open chain ("locking" the knee).

Flexion Screw Home

During flexion, ACL tension helps initiate the “unlocking” by guiding posterior femoral glide and internal tibial rotation.

Highest ACL Strain Activities

Isometric Quad Contraction at 15 deg (30Nm): 4.4% strain

Squatting with Sport Cord (anterior attachment): 4.0% strain

Active flexion-extension with 45N boot: 3.7% strain

Lachman Test (150N anterior shear): 3.0% strain

Squatting (knees over toes): 2.8% strain

Lowest ACL strain Activities

Isometric HS at 30,60 and 90 deg: 0%

Isometric Quads at 60 or 90 deg: 0%

Stationary Biking: 0.6%

Passive flexion-extension: 0.1%

Simultaneous quad + HS at 60/90: 0%

PCL Anatomy (Bundles)

Anterolateral bundle: taut in flexion. 2x as thick as Posteromedial band, allows higher failure load to occur.

Posteromedial bundle: taut in extension.

Primary Function of PCL

Resist restraint of tidal posterior translation and tibial ER

Secondary Function of PCL

Secondary restraint to varus and valgus stresses

Does the PCL Endure More Stress Than the ACL?

Anatomically larger and stronger than the ACL (almost 2× thicker). Also endures more force

Does the PCL Have a Tendency to Heal (Scar Down)?

Yes, it has a higher healing potential than the ACL

Are Isolated PCL Injuries Typically Repaired Surgically?

No

PCL MOI

Direct blow to Proximal Tibia (High energy via MVA)

Fall on the knee with the foot in a PF position

Fall with hyper flexion of the knee

What would be injured if you fall on a flexed knee while DF?

Patella Fx

Tibia is always more anterior compared to?

Femur, opposite in PCL tears, If tibia is sitting posteriorly at rest, suspect PCL injury.

Grading of PCL Injuries

1+: Tibia plateau is slightly posterior to femoral condyles

2+: Tibia plateau is even with femoral condyles

3+: Tibia plateau is posterior to femoral condyles

ACL Injuries - Epidemiology & Risk Factors

11–90% develop tibiofemoral OA within 10 years

Females: 2.4–9.7× more likely than males in same sport

Most common in ages 15–25

70% are non-contact injuries

Greatest predictor of future OA?

Meniscal injury w/ ACL tear due to loss of shock absorption

Does ACL reconstruction help reduce risk of OA?

ACL reconstruction does NOT reduce the risk of OA development. It more prolongs the development

ACL-Deficient Knee - Meniscal Injury Risk

Year 1: 40% risk of meniscal damage

Year 5: 60%

Year 10: 80%

60-80% is degenerative not macro trauma

ACL Injury - Intrinsic Risk Factors

1. Intercondylar Notch Size (Smaller intercondylar notch width = ↑ ACL injury risk)

2. Generalized Ligamentous Laxity (2.7× more likely to tear their ACL)

3. Hormonal Influences (Ovulatory and luteal phases = ↑ estrogen. Estrogen affects: Ligament laxity (collagen remodeling) and Neuromuscular timing

ACL Injury - Extrinsic Risk Factors

1. Shoe-to-Surface Interaction (High friction between cleats and turf increases torsional forces on the knee)

2. Inadequate neuromuscular control allows dangerous combinations of movement, especially during: Deceleration, landing from jumps, cutting or pivoting

Neuromuscular Risk Factors

Ligament Dominance (Valgus and foot placement not width apart)

Quadriceps dominance (Excessive landing contact noise, more stiff, rigid, upright landing)

Leg dominance or Residual Injury Deficits (Thighs not equal side to side during flight, foot contact timing not equal due to being off centered)

Trunk Dominance (Core Dysfunction, thighs do not reach parallel, pause between jumps and does not land in the same footprint

You can only see quadriceps dominance in what view?

Sagittal view

Neuromuscular Control – Additional Risk Factors

1. Mental Fatigue (Cognitive Load)

2. Physical Fatigue

"Glitch in the system"

Are you more likely tear ACL in game or practice?

Games due to higher intensity and unpredictability

Sex Differences in ACL Injury Risk (Female vs. Male Athletes)

1. Decreased Knee Flexion Angle (Stiffer landing with increased peak vertical GRF)

2. Hip Muscle Weakness (Increased dynamic valgus= Femoral IR, tibia ER, foot pronation and hip adduction)

3. Quadriceps Dominance relative to HS (hamstrings not adequately resisting anterior tibial translation, leading to it being increased)

4. Increased Anterior Tibial Translation and Knee valgus (external abduction)

Drop Vertical Jump (DVJ) + LESS Overview

Athlete stands on a 30 cm (12 in) box.

Steps forward off the box (no jumping).

Lands both feet on the ground, then immediately jumps vertically as high as possible.

Video capture is used from frontal and sagittal views for movement analysis. Good for screening and RTS

LESS is scored based on?

17 items but most notably:

Knee flexion angle at initial contact (IC)

Shallow flexion = stiff landing → ↑ ACL load

Stance width

Too wide or too narrow = poor control

Symmetric foot contact at IC

Asymmetry = ↑ unilateral load, potential compensations

Knee valgus displacement

Medial collapse during landing = major ACL injury mechanism

Higher LESS score =?

more errors = higher ACL risk

LESS Score Breakdown

Excellent (0-3)

Good (4-5)

Moderate (6)

Poor (>7)

86% sens

64% spec

Interrater: 84% ICC

Intrarater: 91% ICC

Validation Findings - Poor LESS Scores Are Associated With?

Decreased hip and knee flexion (stiff landings), increased knee vagus, hip adduction angle (medial collapse), increased hip extension moment (ACL strain), and increased internal knee vagus, and hip adduction moment

ACL Injury Prevention - Key Components

Identification of Extrinsic Risk Factors (Neuromuscular) like valgus collapse, asymmetry, poor shock absorption

Strengthening at an appropriate load, neuromuscular training for knee, hip, trunk on stable and unstable surfaces with sports specific drills that emphasize proper alignment and mechanics

2x per week, 30 min a sesh

External or Internal focus will give the best results?

External

Prophylactic ACL Bracing

Used for prevent ACL injury, great for preventing anterior shear forces, but not good at rotary instability

DonJoy Full force is braced is used for?

Post-op ACL

ALL Ligament

Important to limit IR to limit ACL

Medial Ligament Complex is a ?

3-Layer concept, consisting of superficial, middle and deep layers

Superficial Layer of MCL complex

Fascia involving sartorius

Resists Tibia valgus (Abd) + Tibia ER

Middle Layer of MCL Complex

Includes superficial MCL, with structures of the Posteromedial corner (POL and Semimembranosus tendon insertion)

Posteromedial Corner resists?

Valgus + Posterior translation of tibia

Deep Layer of MCL complex

Represents true capsule of joint (deep MCL and includes meniscotbial and meniscofemoral ligaments

Resists valgus force

Tear of the medial ligament complex is usually from?

Deep to superficial around the joint line or femoral insertion

Contact MOI of MCL

Blow or force outside of knee/thigh that creates valgus

Non-Contact MOI of MCL

Tibia ER + Abduction stretching the medial ligament complex

Grade 1 of MCL Sprain

Microtrauma with no elongation

Exam Findings: Tender Ligament + Normal Valgus Laxity. May have pain at end ranges of motion

Laxity: 0-5mm

Grade 2 of MCL Sprain

Elongated but intact

Exam Findings: Increased valgus laxity with firm endpoint on valgus stress at 20 deg of knee flexion

Laxity: 5-10mm

Grade 3 of MCL Sprain

Complete disruption

Exam findings: Increased valgus laxity with soft endpoint on vagus stress at 30 deg of knee flexion. May be painful early on

Laxity: >10mm

Grade 1 and 2 MCL sprains are usually treated?

Conservative

Posteromedial Corner (PMC) Anatomic Components

Semimembranosus Insertion ("Semimembranosus Corner")

Posterior Oblique Ligament (POL)

Oblique Popliteal Ligament (OPL)

Posterior One-Third of the Medial Meniscus

Injury to the PMC can result in?

Anteromedial rotary instability (involving the MCL and POL)

Posteromedial rotary instability (due to damage to the posteromedial capsule, including semimembranosus, OPL

Valgus instability, accompanied by ACL injury 73/93 times

Grade lll POL typical require?

Surgical Reconstruction

Anteromedial Rotary Instability + test would show?

Anterior translation of the medial tibial plateau + Tibia ER

Posteromedial Rotary instability + test would show?

Posterior translation of the medial tibial plateau + Tibia IR

How would you test Anteromedial Rotary Instability?

1. (Anteromedial drawer variant)

Patient: Supine, knee flexed to 90°

Tibia is placed in 15° external rotation

Examiner applies an anterior drawer force to the tibia+ Test: Excessive anterior displacement of the medial tibial plateau

➡️ Indicates MCL + POL + possibly ACL injury

How would you test posteormedial rotary instability?

Posterior Drawer with Tibial Internal Rotation

Patient: Supine, knee flexed to 90°

Examiner applies a posterior drawer force while keeping tibia in internal rotation (30 deg)

+ Test: Excessive posterior translation of the medial tibial plateau relative to lateral side

➡️ May produce a "medial sag"

Post-operative rehab is based on associated ligament reconstruction of?

ACL/PCL injuries

Posterolateral Corner (PLC) Anatomical Component

Fibular Collateral Ligament (LCL)

Arcuate Ligament Complex (Popliteofibular Ligament, Fabellofibular Ligament, Popliteus Tendon)

Posterolateral corner can be injured in?

Isolation

PLC primary functions

Resists varus stress and controls external rotation of the tibia

Provides posterolateral rotational stability

PLC works with PLC due to?

Both resist posterior tibial translation, especially under varus and external rotation stress

Dial Test for PLC Rotary Instability

Purpose: Detects increased external rotation of the tibia — sensitive for PLC and/or PCL injury.

Procedure:

Patient is prone (can also be done supine), knees flexed to 30° and 90°

Stabilize the thigh, and externally rotate the lower legs

Interpretation:

Increased external rotation (>10–15°) on one side:

At 30° only: PLC injury

At both 30° and 90°: PLC + PCL injury

At 90° only: More suggestive of isolated PCL injury

If Varus test + tests at 0 deg and 20-30 deg?

0 deg: More structures involved (PLC + Cruciates)

20-30 deg: LCL Isolated

Straight Anterior Instability

Anteromedial bundle of ACL is lax

Anterolateral instability

Involves ACL, ITB, arcuate ligament complex and ALL

Posteromedial Instability

PMC, PCL and POL

Posterolateral Instability

Involves PCL, LCL and PLC

AnteroMedial Instability

Involves ACL, MCL, POL and PMC

Anterior Transition Restraints

Primary: ACL

Secondary: MCL, LCL, Middle and posterior 1/3 of medial/lateral capsule, PMC, and IT band

Posterior Translation Restraints

Primary: PCL

Secondary: MCL, LCL, posterior 1/3 of medial/lateral capsule, polities tendon, and A/P meniscofemoral ligaments

Valgus Restraints

Primary: MCL

Secondary: ACL, PCL, middle 1/3 of medial capsule, posterior oblique ligament

Varus Restraints

Primary: LCL

Secondary: ACL, PCL, ITB, Middle 1/3 of lateral capsule, posteorlateral corner (arcuate complex)

Lateral Rotation Restraints

Primary: MCL/LCL

Secondary: PLC (arcuate complex)

Medial Rotation Restraints

Primary: ACL

Secondary: PMC + Meniscofemoral ligaments