Keywords

Anterior Cruciate Ligament (ACL) [1, 2]

Anatomy/Biomechanics

  • Primary restraint to anterior translation of the tibia relative to the femur

  • Secondary restraint to tibial rotation

  • Anteromedial (AM) bundle:

    • More isometric

    • Tight in flexion

  • Posterolateral (PL) bundle:

    • Tight in extension

    • Contributes primarily to rotational stability

Diagnosis

History

  • Contact or noncontact sports injury

  • Pivoting knee injury

  • “Pop” followed by knee effusion (swelling)

Physical Exam

  • Anterior drawer

  • Lachman exam:

    • Anteriorly directed force on the tibia with the knee flexed 30°

    • Grading:

      • I = 3–5 mm translation

      • II = 6–10 mm

      • III > 10 mm:

        • ° A = Firm endpoint

        • ° B = Soft endpoint

  • Pivot shift exam:

    • Valgus force as the knee is brought from extension into flexion.

    • In extension, the tibia subluxated anteriorly and reduces at 20–30° of flexion as IT band transitions from knee extensor to flexor thus reducing the tibia.

Imaging

  • X-ray:

    • “Segond fracture,” avulsion fracture off the anterolateral proximal tibia; classically associated with ACL rupture

  • MRI: definitive diagnosis

Treatment

Nonoperative

  • Low-demand patients

  • Primarily consists of activity/lifestyle modification

  • PT to emphasize hamstring strength

  • ACL specific bracing with activity

Operative

  • Active, high-demand patients.

  • Failed nonoperative treatment (persistent knee instability).

  • Reconstruction is current gold standard (as opposed to repair).

Surgical Options

  • Single vs. double bundle:

    • Double bundle may better reproduce knee kinematics [3].

    • No clear difference in clinical outcomes between single and double bundle.

  • Graft choice:

    • Hamstring (semitendinosus, gracilis):

      • ° Smaller patients yield smaller grafts:

        • Graft size <8 mm associated with higher risk of failure [4]

      • ° No bone-bone healing

    • Bone-patellar tendon-bone:

      • ° Longest history of use

      • ° “Gold standard”

      • ° Bone-bone healing

      • ° Donor-site morbidity (anterior knee pain)

      • ° Complication – patella fracture

    • Quadriceps tendon

  • Allograft vs. autograft [5]:

    • Autograft:

      • ° Pro: patient’s own tissue, no risk of disease transmission, and faster graft incorporation

      • ° Cons: donor-site morbidity

    • Allograft:

      • ° Pro: no donor-site morbidity and can select graft size.

      • ° Cons: slower graft incorporation, theoretic risk of disease transmission, and irradiated allograft may be associated with higher failure rates.

  • Femoral tunnel drilling:

    • Transtibial:

      • ° More “traditional” technique

      • ° Femoral tunnel location accessed via the tibial tunnel

    • Independent tunnel:

      • ° May allow for more “anatomic” femoral tunnel placement by allowing more oblique drill trajectory

      • ° Requires knee hyperflexion to prevent posterior wall “blowout”

    • Retrograde or “outside-in” drilling:

      • ° Requires specialized instrumentation

      • ° Allows independent femoral tunnel drilling without need for knee hyperflexion

Rehab/Injury Prevention [6]

  • Neuromuscular training/jump training

  • Jump landing in valgus and relative extension implicated in increased risk of injury

  • Address relative hamstring weakness

Complications

  • Re-rupture:

    • Most common cause – tunnel malposition

  • Loss of motion/arthrofibrosis:

    • Delay surgery until patients regain motion and swelling from acute injury controlled

  • Tunnel osteolysis

  • Fixation failure

  • “Cyclops” lesion:

    • Due to fibroproliferative tissue within the intercondylar notch

    • Blocks extension

    • Treat with arthroscopic debridement

  • Posttraumatic arthritis:

    • May be associated with concomitant meniscal pathology

Posterior Cruciate Ligament (PCL) [7, 8]

Anatomy/Biomechanics

  • Anterolateral (AL) bundle:

    • Tight in flexion

  • Posteromedial (PM) bundle:

    • Tight in extension

  • Meniscofemoral ligaments:

    • Originate from posterior horn lateral meniscus and insert onto PCL

    • Anterior, ligament of Humphrey; posterior, ligament of Wrisberg

Diagnosis

History

  • Posteriorly directed blow to the flexed knee (i.e., “dashboard” injury)

  • Knee hyperflexion injury with the plantar-flexed foot

Physical Exam

  • Posterior drawer test:

    • Grading:

      • ° I = 1–5 mm translation

      • ° II = 6–10 mm

      • ° III > 10 mm

  • Posterior sag sign:

    • With the knee at 90° flexion, the tibia lies posterior relative to the femoral condyles compared to contralateral side.

  • Quadriceps active test:

    • With the knee flexed at 90°, the tibia subluxated posteriorly relative to the femur; resisted activation of the quadriceps reduces the tibia anteriorly.

  • Dial test:

    • See section below (posterolateral corner injuries).

Imaging

  • X-ray:

    • May show avulsion fracture off posterior tibial insertion

    • Posterior drawer stress test → posterior subluxation of the tibia

  • MRI

Treatment [9]

Nonoperative

  • Most isolated PCL tears (Grade I–II)

  • Rehab to concentrate on quadriceps strengthening

Operative

  • Isolated Grade III tears with persistent functional instability

  • Multi-ligament knee injury

Surgical Options

  • Tibial avulsion fracture → direct repair

  • Reconstruction options:

    • Transtibial technique:

      • ° Beware of “killer turn”:

        • PCL graft is passed from anterior to posterior through tibial tunnel; graft then passed from posterior to anterior into femoral tunnel.

        • May cause attenuation of graft tissue.

    • Tibial inlay technique:

      • ° Avoids “killer turn”:

        • Tibial portion of graft seated into the socket in posterior aspect of the tibia

    • Graft choice:

      • ° Allograft vs. autograft:

        • Same inherent issues as above.

        • Allograft affords more graft options especially during multi-ligament knee reconstruction.

Medial Collateral Ligament (MCL) [10]

Anatomy/Biomechanics

  • Superficial MCL:

    • Primary restraint to valgus stress of the knee

  • Deep MCL:

    • Secondary restraint to valgus stress.

    • Attaches to the medial meniscus.

    • Posterior fibers blend with the posteromedial capsule and the posterior oblique ligament (POL).

Diagnosis

History

  • Commonly associated with ACL rupture

Physical Exam

  • Tenderness along medial aspect of the knee.

  • Valgus stress testing at 30° knee flexion isolates superficial MCL.

  • Grading:

    • I = 1–4 mm medial joint line gapping

    • II = 5–9 mm

    • III ≥ 10 mm

  • Valgus stress at 0° knee flexion indicates posteromedial capsule or cruciate ligament injury.

Imaging

  • X-ray:

    • Rule out bony injury.

    • Valgus stress test may show medial joint line gapping.

  • MRI:

    • Can characterize sprain vs. partial vs. complete tear

Treatment

Nonoperative

  • Primary treatment in both isolated and combined ACL injury

  • NSAIDs, rest, physical therapy, and bracing (to resist valgus)

Operative treatment

  • Relative indications:

    • Acute repair in Grade III (complete) injuries

    • Multi-ligament knee injury

  • Reconstruction indicated in chronic injuries with persistent functional instability

Posterolateral Corner (PLC) [11, 12]

Anatomy/Biomechanics [13]

  • PLC structures consist of static and dynamic structures:

    • Static:

      • ° Lateral collateral ligament (LCL)

      • ° Popliteus tendon

      • ° Popliteofibular ligament (PFL)

      • ° Lateral capsule

      • ° Arcuate ligament

      • ° Fabellofibular ligament

    • Dynamic:

      • ° Biceps femoris

      • ° Popliteus muscle

      • ° Iliotibial band

      • ° Lateral head of gastrocnemius

  • PLC resists external rotation, varus, and posterior translation.

Diagnosis

History

  • Acute injuries:

    • Be suspicious with high-energy injury mechanisms and multi-ligamentous knee injury (i.e., knee dislocation).

Physical Exam

  • Varus thrust with gait exam

  • Varus stress at 30° knee flexion:

    • Grading:

      • ° I = 0–5 mm lateral joint line gapping

      • ° II = 6–10 mm

      • ° III > 10 mm

  • Varus laxity at 0° (LCL + cruciate injury)

  • Dial test:

    • Tests for isolated PLC vs. PLC + PCL injury.

    • External rotation of tibia at 30° and 90° of knee flexion.

    • Positive test is >10° of side-to-side difference:

      • ° + test @ 30° and 90° flexion → PLC + PCL injury

      • ° + test @ 30° flexion only → isolated PLC injury

  • Reverse pivot shift:

    • Valgus/external rotation force as the knee is brought from flexion into extension.

    • In flexion, the tibia subluxated posteriorly and reduces at approximately 20–30° of flexion as IT band transitions from knee flexor to extensor.

Imaging

  • X-rays:

    • Avulsion fracture off the fibula (“arcuate fracture”) represents bony avulsion of lateral ligamentous complex.

  • MRI:

    • Imaging of choice

Treatment

Nonoperative

  • Isolated PLC Grade I/II injuries

  • Knee immobilizer with protected weight-bearing ×2 weeks followed by progressive rehab

Operative

  • PLC repair:

    • Indicated only in acute injuries (within 2 weeks from injury)

    • Fibular avulsion → ORIF

  • PLC reconstruction:

    • Grade III injury

    • Chronic injuries

    • Correct varus malalignment (if present) with high tibial osteotomy in chronic injuries

  • Reconstruction techniques:

    • Multiple described

    • Goal: reconstruct LCL and PFL

  • Acute multi-ligament knee injury:

    • Staged reconstruction:

      • Repair/reconstruct PLC early (within 2 weeks of injury).

      • Reconstruct PLC prior to ACL.

Complications

  • Knee stiffness/arthrofibrosis

  • Missed PLC injury:

    • Unrecognized PLC injury may lead to failed ACL reconstruction.

  • Peroneal nerve injury