Knee Ligament Injuries
What is O'Donohue's or the Terrible Triad?
A combination of ACL, medial meniscus, and MCL injury
What is the typical MOI of an ACL tear?
A cut-and-plant movement or sudden change in speed with the foot firmly placed Rapid deceleration moments such as planting the affected leg to cut and change direction as well as landing from a jump, pivoting, twisting, and direct impact to the front of the tibia
Posterolateral rotary instability MOI
A direct blow to the anteromedial knee with the tibia in ER
What structures are affected with anterolateral rotary instability (ALRI)?
ACL, LCL, posterolateral capsule, and arcuate complex
ACL is the primary restraint to?
Anterior tibial subluxation
The ACL has 2 bands. What directions do they run?
Anteromedial Posteriolateral (Important because the graft they use, they want to mimic these bundles - so now they do a double bundle graft)
Which type of grafts are the most common?
Autografts (patellar bone and hamstring) and allografts are most common but there is no consensus which provides the most stability
What would you work on in an ACL neuromuscular prevention program?
Balance training (balance exercises) Jump training (landing with increased flexion at the knee and hip) Skill training (controlling body motions, especially in deceleration and pivoting maneuvers) Movement education and some form of feedback to the athlete during training of these activities Agility training (agility exercises)
Why is the LCL not automatically associated with a meniscal tear?
Because it is not connected with the lateral meniscus (However, an LCL injury often occurs with other ligament injuries)
Why are posterolateral rotary instabilities difficult to detect/diagnose?
Because they often occur with concomitant ligamentous injuries
Tibial plateau fractures can be associated with an ACL tear. What causes this? Which are most common?
Caused by varus or valgus forces with axial loading Lateral tibial plateau fractures (Segond fracture) is most common
_____ N injuries occur up to 30% of the time with posterolateral rotary instability.
Common fibular N
What is MOI for anteromedial rotary instability?
Contact/non-contact Flexed knee and valgus stress ER of tibia or IR of femur
What is the MOI of ALRI?
Contact/non-contact Hypertension with varus and IR stress IR of tibia or ER of femur
What test is used to asses rotary instability?
Dial test
How do PCL tears occur?
Direct blow to the front of the tibia with the knee flexed is the most frequent MOI Forced hyperextension is another common MOI Can also result from a car accident in which a posterior force is applied to the tibia when the flexed knee hits the dashboard (dashboard injury)
What test can be used for assessing ALRI?
Drawer test with tibia in IR Lateral pivot shift test
The typical ACL injuries occur with the tibia in what position? Explain why.
ER and in 10-30 degrees of flexion with the knee in a valgus position The ground reaction force falls medial to the joint during a cutting maneuver and this added force may tax an already tensioned ACL
Rotary instabilities result in:
Excessive rotation of the tibia in relation to the femur
If the knee is unstable in full ___, it is suggestive of an LCL/PCL injury?
Extension
LCL is taut in? Looser in?
Extension Flexion
MCL becomes taut in? Looser in?
Extension Flexion
PCL becomes taut with what movement? Looser in?
Flexion Extension
A popliteal (Baker's) cyst can be associated with an ACL tear. What is this? What does it result from?
Forms when a bursa swells with synovial fluid Results from chronic effusion and intraarticular lesions
When is the ACL taut? When is it loose?
Full knee extension and loose in mid flexion
What are xenografts?
Grafts taken from animals; bovine xenografts in particular have been associated with high complication rate
What are allografts?
Grafts taken from cadavers
There are multiple types of rotary instability, however the majority of research focuses on the impact of the structures in the posterolateral corner (PLC). What are these structures?
IT band Biceps femoris tendon Lateral gastroc Arcuate ligament LCL Popliteus Popliteofibular ligament
What will patients present with clinically if they have posterolateral rotary instability?
Joint line tenderness with swelling in the posterolateral corner Episodes of knee buckling during the stance phase of gait or with pivoting movements Some patients present with unpredictable giving way without provocation or simply when just standing
LCL injuries may occur with:
Knee dislocation Distal IT band injury Popliteus rupture Posterolateral capsule injury Fibular N injury
What structures in the PLC work together to stabilize the knee by restraining varus, tibial ER, and posterior translation?
LCL Popliteus tendon Popliteofibular ligament
A posterolateral corner injury can be associated with an ACL tear. What structures provide stability of the posterolateral corner of the knee? This injury is associated with rupture of what? Failure to address the instability of these structures results in what?
LCL, popliteus, and the posterolateral capsule One of both of the cruciate ligaments Increases the forces at the ACL and PCL graft sites, and may ultimately predispose to failure of the cruciate reconstruction
Describe a grade III ligament sprain.
Ligament fibers are completely torn There is pain during the initial injury but then it subsides (no fibers are attached anymore; tenderness may continue to be present) There may be a lot of swelling Hemarthrosis may occur within 1-2 hours Feels unstable or gives out at certain times There may be rotational instability End feel is empty "Pops" during initial injury
Describe a grade II ligament sprain.
Ligament fibers are partially torn with hemorrhaging There is a little tenderness and moderate swelling The joint may feel unstable or give out during activity Increased joint laxity yet there is still a firm end point
Describe a grade I ligament sprain.
Ligament fibers are stretched but there is no tear There is a little tenderness and swelling The knee does not feel unstable or give out during activity No increased laxity and there is a firm end feel
How is knee stability maintained?
Ligaments, muscles, menisci, and bony contours
LCL tear examination
Look for instability in full extension Palpation could reveal tenderness over the posterolateral knee No significant joint effusion, unless there is a also a cruciate ligament or meniscal injury
Which are more common: MCL or LCL injuries?
MCL (LCL injuries are much less common)
What is the gold standard for the medical diagnostics of ligamentous injury?
MRI (will also reveal associated meniscal tears, chondral injuries, or bone bruises)
Bone contusions can be associated with an ACL tear. Why might this occur? What structures does this often involve?
May occur due to the pressure on the knee with trauma Bony lesions have been reported in 84-98% of ACL injuries Often involve either the lateral femoral condyle, the lateral tibial plateau, or both The bony bruising itself is unlikely to significantly reduce friction
More than 50% of all ACL ruptures have associated ____ lesions.
Meniscal
How do MCL tears occur?
Mostly occur after an impact on the outside of the knee With the foot fixated to the ground, the combined movement of flexion/valgus/tibial ER will place excessive tension on the MCL
Do clinical forces equal functional forces in ligament testing?
NO (it can be hard to match functional forces in the clinic, but a little laxity with a clinical force can mean a significant amount of laxity with functional activities)
What should you look for in an MCL examination?
Normally isolated swelling is seen on the medial part of the knee (swelling may be minimal) Palpation along the joint line may be tender The reported MOI Feels/hears "pop" or "snap" Knee "stiffens up" within hours of injury Walking may not be significantly limited
Explain the typical clinical presentation of an ACL tear.
Occurs after either a cutting maneuver, landing or jumping There may be an audible pop at the time of injury A feeling of initial instability which may be masked later by extensive swelling Episodes of "giving way" especially on pivoting or twisting motions Initially injury is extremely painful Swelling may be immediate and extensive, but can be minimal or delayed Restricted movement, especially an inability to fully extend
Chondral injuries can be associated with an ACL tear. When does this occur?
Occurs at the time of initial impact *Chondral degradation is common years after an ACL injury
With ACL reconstructions, autografts taken from the patient's own body can include portions of what structures?
Patellar tendon Semitendinosus tendon IT band Gracilis tendon
Anteromedial rotary instability (AMRI) involves what structures
Posterior horn medial meniscus, oblique popliteal ligament, ACL, MCL
PCL is the primary restraint to what? Secondary restraint to what?
Posterior tibial movement Hyperextension and tibial rotation
Ligaments can be primary and/or secondary restraints. Explain.
Primary restraint signifies the structure that is the major restraint to movement Secondary restraint has some significant function in resisting displacement but isn't the major restraint
What is the purpose of a KT1000 arthrometer?
Provides an objective measurement of anterior tibia translation Can be particularly useful when pain and guarding preclude evaluation Can be used as part of the follow up examination after ACL reconstruction
ACL is the secondary restraint to?
Rotation in both directions
In the absence of the primary restraint, what happens?
Secondary structures are put under larger tension to restrain the same force
What is a special test that can be used for assessing AMRI?
Slocum test (drawer test with tibia in ER)
How might a combined PCL injury present clinically? (PCL combined with other ligamentous injuries)
Swelling, bruising, anterior and posterior knee pain, a feeling of instability, limited ROM, and difficulty walking
Which part of the MCL gets damaged first? Why is this important?
The deep portion It may lead to medial meniscal or ACL damage
T/F ACL tear MOIs are 30% direct contact and 70% are non-contact.
True
T/F High-speed activities such as cutting or landing maneuvers, require eccentric muscle action of the quadriceps to resist further flexion. ACL tears occur when this doesn't happen.
True
T/F Injuries to ACL rarely occur in isolation. The presence and extent of other injuries may affect the way in which the ACL injury is managed.
True
T/F LCL injuries usually respond to conservative management.
True
T/F Synthetics (such as Gore-Tex) can be used as grafts for ACL tears.
True
T/F The MCL has both superficial and deep portions. The deep portions have an extensive attachment to the meniscus and capsule.
True
T/F The PCL is twice as thick as the ACL which results in less injuries than the ACL.
True
T/F With MCL tears, the individual might feel an immediate pain or feel/hear a "pop".
True
T/F With disruption of the ACL, the MCL provides most of the anterior stability.
True
T/F You should rule out a PCL tear before you rule out an ACL tear.
True
MCL is the primary restraint to what type of forces? Secondary to?
Valgus Anterior knee stability
What special test can you do to assess MCL injury?
Valgus stress test at 20-30 degrees flexion (beware of muscle guarding) Remember to palpate the joint line
The LCL is a primary restraint to? Secondary restraint to?
Varus stress Anterior and posterior stress
What special test can you do to assess for an LCL tear?
Varus stress at 30 degrees flexion
How will an isolated PCL injury present clinically?
WIll often have minimal pain, swelling, instability, and full ROM The individual may also have a near-normal gait pattern
How do LCL injuries occur?
With a varus stress Usually with contact
Women or men are 3X more likely to have ACL injuries. Why?
Women Smaller intercondylar notch Wider pelvis and greater Q angle Neuromuscular factors Hormonal variations may alter the laxity of ligaments