- See: Biomechanics of the ACL:
- length of 38 mm (range 25 to 41 mm)
- width of 10 mm (range 7 to 12 mm)
- made up of multiple collagen fascicles;
- surrounded by an endotendineum
- microspocially: interlacing fibrils (150 to 250 nanomet in diamter
- grouped into fibers (1 to 20 um in diameter)
- synovial membrane envelvope
- receives its innervation from tibal nerve;
- infiltrates the capsule posteriorly;
- golgi tendon receptors;
- A sensory role for the cruciate ligaments.
- Mechanoreceptors in human cruciate ligaments. A histological study.
- Neural anatomy of the human anterior cruciate ligament.
- Proprioception after rupture of the anterior cruciate ligament. An objective indication of the need for surgery.
- blood supply:
- major blood supply: from middle genicular artery:
- supplied by the middle genicular artery;
- bony attachments do not provide a significant source of blood to distal or proximal ligaments;
Microvasculature of cruciate ligaments and its response to injury. An experimental study in dogs.
- Femoral and Tibial Attachments:
- femoral attachment:
- ACL arises from the posteromedial corner of medial aspect of lateral femoral condyle in the intercondylar notch;
- attachment is actually an interdigitation of collagen fibers & rigid bone thru transitional zone of
fibrocartilage and mineralized fibrocartilage;
- femoral attachment of ACL is on posterior part of medial surface of lateral condyle well posterior to longitudinal axis of the
- tibial attachment:
- tibial attachment is in a fossa in front of & lateral to anterior spine, a rather wide area from 11 mm in width to 17 mm in AP direction;
- anterior fibers go forward to level of transverse meniscal ligament;
- inserts into the interspinous area of the tibia;
- Anterior & Posterior Bundles:
- ACL is composed of two principal parts: small anteromedial band and a larger bukly posterolateral portion;
- anteromedial bundle is tight in flexion and the posterolateral bundle is tight in extension;
- extension: both bundles are parallel;
- femoral insertion site of the posterolateral bundle moves anteriorly
- both bundles are crossed
- anteromedial bundle tightens and posterolateral bundle loosens;
- ref: Functional anatomy of the anterior cruciate ligament. Fibre bundle actions related to ligament replacements and injuries.
- posterolateral bundle:
- represents posterior directly directed fibers w/ its attachment just lateral to midline of the intercondylar eminence and slightly lateral to most lateral
attachement of the intermediate bundle;
- anteromedial portion is tight in flexion whereas the posterolateral bulky portion of ligament is tight in extension (and internal rotation);
- unlike the antermedial portion, the bulkier posterolateral bundle is not isometric.
- interruption of posterolateral bundle of ACL increases external rotation recurvatum test of posterolateral after anteromedial and intermediate
bundles are divided;
- w/ knee extended, resistance to the anterior drawer test is by posterolateral bulky portion;
- it limits anterior translation, hyperextension, and rotation;
- oblique position of the posterolateral bundle provides more rotational control than is provided by the anteromedial bundle, which is in a more axial position;
- hyperextension and internal rotation place the posterolateral bundle at greater risk for injury;
- rupture cause increases in hyperextension, anterior translation (extended knee), increase in external and internal rotation (knee extended),
and increases in external rotation with the knee in mid flexion;
- anteromedial bundle:
- femoral insertion of the anteromedial bundle is the center of rotation of ACL
- anteromedial bundle has isometric behavior;
- anteromedial bundle tightens in flexion while the posterolateral bundle relaxes in flexion.
- is more prone to injury with the knee in flexion
- anteromedial bundle inserts on the medial aspect of the intercondylar eminence of the tibia and forms the medial corner of the triangle;
- anteromedial band is primary check against anterior translation of tibia on femur when anterior drawer test is performed in usual manner w/ knee flexed;
- cutting this ligament may produce anterolateral instability;
- limits anterior translation of the tibia on the femur with the knee in flexion (which requires isometric behavior);
- rupture may cause in an increase in anterior translation in flexion, minimal increase in hyperextension, and minimal rotational instability;
- intermediate bundle:
- cutting this ligament produces straight anterior instability;
- when anteromedial band of the ligament is torn, posterolateral bulk of ligament may remain intact & anterior drawer sign will be present but surgeon will
have impression that ligament is not torn;
- Functional anatomy of the anterior cruciate ligament. Fibre bundle actions releated to ligament replacements and injuries.
Functional anatomy of the anterior cruciate ligament and a rationale for reconstruction.
Anatomy of the anterior cruciate ligament.