Anterior Cruciate Ligament Injury & Reconstruction
Medical Background
I. Other Names5
ACL injury
ACL tear
ACL sprain
Ireland calls this a “heart attack of the knee.”
II. Definition15
An ACL injury is a tear or sprain of the anterior cruciate ligament (ACL)
ACL reconstructionis replacement of the torn ACL with a graft of tendon harvested from elsewhere in the knee.
III. Grading/Types/Classifications1,8,13
Injured ligaments are considered "sprains" and are graded on a severity scale.
Grade 1 Sprain The ligament is mildly damaged. It has been slightly stretched, but is still able to help keep
the knee joint stable.
Grade 2 Sprain A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often
referred to as a partial tear of the ligament
Grade 3 Sprain This type of sprain is most commonly referred to as a complete tear of the ligament. The
ligament has been split into two pieces, and the knee joint is unstable.
The severity of the ACL injury was graded using a 4-point system:
Grade 0 injury - intact ligament;
Grade 1 injury - partial tear with less than half of the ligament substance disrupted;
Grade 2 injury - partial tear with more than half of the ligament substance disrupted
Grade 3 injury - a complete tear
Partial ACL tear included 1 or more of the following: preserved ligament continuity with abnormal signal intensity,
preserved ligament continuity with diffuse or focal thinning, or an undulating contour of the ligament with discernable
femoral and tibial attachments.
To differentiate grade 1 and 2 injuries, marked thinning, decreased slope, or an undulating ligament contour were
considered as indicators of grade 2 injury
“O Donoghue’s unhappy triad” 1
Indicates injuries to medial structures (MCL) + ACL tear + medial meniscus injury.
IV. Etiology
, MOI for unhappy triad: Abduction, flexion and internal rotation of femur on tibia (Ab FIR) - This causes damage to
medial structures,like tibial collateral, medial capsule and if more force is applied ACL and medial meniscus may also tear.
1
9
There are three main ACL injury mechanisms: direct contact, indirect contact, and noncontact.
Direct contact - Are sustained when a person or object strikes the knee directly.
injuries
Indirect contact - Occur when a person or object strikes a part of the body other than the knee itself,
injuries causing excessive forces to be transferred through the knee (such as a direct blow the
thigh, translating the femur posterior in respect to the tibia), resulting in ACL failure.
Noncontact - Sustained when a deceleration or change in direction (pivot) force are applied to the
injuries knee but often encompass an ill-timed neuromuscular firing of structures around the
knee, causing translation of the tibia on the femur, which results in ACL failure.
Noncontact mechanisms account for 60%–70% of ACL injuries.
The common mechanisms are: 5
o Planting and cutting (Changing direction rapidly): 29%.
o Straight knee landing: 28%.
o Landing with knee hyperextended: 26%.
Car accidents 3
Falling down stairs 3
V. Risk Factors2,3,5
Young people, particularly those in their adolescence, tend to sustainmore ACL injuries, because they’re the most
physically active.
Athletes who plays dynamic cutting, pivoting, jumping, and tackling sports, such as soccer, basketball, skiing and
football
Women
Due to:
o Narrow femoral notch, (the passage at the bottom of the femur (thigh bone)
where the ACL attaches to the femur and tibia to cross the knee joint)
o wider hips (the wider pelvis, increased femoral anteversion, and the genu
valgum)
o Genu valgum
o greater foot pronation
o larger Q angle (angle of quadriceps relative to the patellar tendon insertion
through the center of the kneecap)
o females don’t carry the muscle mass or strength than males
o An increase in estrogen, can contribute to joint laxity—i.e., looser, less
stable joints—and increased flexibility, and have a negative impact on
neuromuscular coordination. Females experience a rapid surge of estrogen
just prior to ovulation, usually between days 10 and 14 of the cycle.
o Men have three times more knee bend (flexion) than women when decelerating while landing. At the same
point in time, women not only land with straighter legs, but have increased knee valgus. The study theorizes that
the imbalance in hamstrings-to-quadriceps strength is to blame. Females tend to have stronger quadriceps than
hamstrings, creating an unstable environment for the knees. The over-firing of the quads may prevent the female
Medical Background
I. Other Names5
ACL injury
ACL tear
ACL sprain
Ireland calls this a “heart attack of the knee.”
II. Definition15
An ACL injury is a tear or sprain of the anterior cruciate ligament (ACL)
ACL reconstructionis replacement of the torn ACL with a graft of tendon harvested from elsewhere in the knee.
III. Grading/Types/Classifications1,8,13
Injured ligaments are considered "sprains" and are graded on a severity scale.
Grade 1 Sprain The ligament is mildly damaged. It has been slightly stretched, but is still able to help keep
the knee joint stable.
Grade 2 Sprain A Grade 2 Sprain stretches the ligament to the point where it becomes loose. This is often
referred to as a partial tear of the ligament
Grade 3 Sprain This type of sprain is most commonly referred to as a complete tear of the ligament. The
ligament has been split into two pieces, and the knee joint is unstable.
The severity of the ACL injury was graded using a 4-point system:
Grade 0 injury - intact ligament;
Grade 1 injury - partial tear with less than half of the ligament substance disrupted;
Grade 2 injury - partial tear with more than half of the ligament substance disrupted
Grade 3 injury - a complete tear
Partial ACL tear included 1 or more of the following: preserved ligament continuity with abnormal signal intensity,
preserved ligament continuity with diffuse or focal thinning, or an undulating contour of the ligament with discernable
femoral and tibial attachments.
To differentiate grade 1 and 2 injuries, marked thinning, decreased slope, or an undulating ligament contour were
considered as indicators of grade 2 injury
“O Donoghue’s unhappy triad” 1
Indicates injuries to medial structures (MCL) + ACL tear + medial meniscus injury.
IV. Etiology
, MOI for unhappy triad: Abduction, flexion and internal rotation of femur on tibia (Ab FIR) - This causes damage to
medial structures,like tibial collateral, medial capsule and if more force is applied ACL and medial meniscus may also tear.
1
9
There are three main ACL injury mechanisms: direct contact, indirect contact, and noncontact.
Direct contact - Are sustained when a person or object strikes the knee directly.
injuries
Indirect contact - Occur when a person or object strikes a part of the body other than the knee itself,
injuries causing excessive forces to be transferred through the knee (such as a direct blow the
thigh, translating the femur posterior in respect to the tibia), resulting in ACL failure.
Noncontact - Sustained when a deceleration or change in direction (pivot) force are applied to the
injuries knee but often encompass an ill-timed neuromuscular firing of structures around the
knee, causing translation of the tibia on the femur, which results in ACL failure.
Noncontact mechanisms account for 60%–70% of ACL injuries.
The common mechanisms are: 5
o Planting and cutting (Changing direction rapidly): 29%.
o Straight knee landing: 28%.
o Landing with knee hyperextended: 26%.
Car accidents 3
Falling down stairs 3
V. Risk Factors2,3,5
Young people, particularly those in their adolescence, tend to sustainmore ACL injuries, because they’re the most
physically active.
Athletes who plays dynamic cutting, pivoting, jumping, and tackling sports, such as soccer, basketball, skiing and
football
Women
Due to:
o Narrow femoral notch, (the passage at the bottom of the femur (thigh bone)
where the ACL attaches to the femur and tibia to cross the knee joint)
o wider hips (the wider pelvis, increased femoral anteversion, and the genu
valgum)
o Genu valgum
o greater foot pronation
o larger Q angle (angle of quadriceps relative to the patellar tendon insertion
through the center of the kneecap)
o females don’t carry the muscle mass or strength than males
o An increase in estrogen, can contribute to joint laxity—i.e., looser, less
stable joints—and increased flexibility, and have a negative impact on
neuromuscular coordination. Females experience a rapid surge of estrogen
just prior to ovulation, usually between days 10 and 14 of the cycle.
o Men have three times more knee bend (flexion) than women when decelerating while landing. At the same
point in time, women not only land with straighter legs, but have increased knee valgus. The study theorizes that
the imbalance in hamstrings-to-quadriceps strength is to blame. Females tend to have stronger quadriceps than
hamstrings, creating an unstable environment for the knees. The over-firing of the quads may prevent the female
