Trauma and orthopaedics (2): The knee (II) Flashcards
Anterior cruciate ligament (ACL)
The ACL is an important stabiliser of the knee joint, being the primary restraint to limit anterior translation of the tibia (relative to the femur) and also contributing to knee rotational stability (particularly internal).
Consequently, a tear of this important ligament often results in significant functional impairment of the joint
Anterior cruciate ligament (ACL) tear mechanism of injury
- without injury
- sudden change of direction twisting the flexed knee
an athlete history of twisting knee whilst weight bearing
Anterior cruciate ligament (ACL) tear presentation
- rapid joint swelling
- signif pain
- if delayed presentation- instability ‘leg giving way’
special tests for ACL tear
Lachman Test and Anterior Draw Test
lachmans test
involves placing the knee in 30 degrees of flexion and, with one hand stabilising the femur, pulling the tibia forward to assess the amount of anterior movement of the tibia compared to the femur. The other knee is then examined for comparison
anterior draw test
The anterior draw test involves flexing the knee to 90 degrees, placing the thumbs on the joint line and their index fingers on the hamstring tendons posteriorly. Force is then applied anteriorly to demonstrate any tibial excursion, which is then compared to the opposite site.
Lachman’s test is the more sensitive of the two tests for an ACL tear.
investigation for ACL tear
X-ray (AP and lateral) to exclude bony injury, any joint effusion or lipohaemarthrosis
MRI is gold standards for ACL diagnosis (also picks up meniscal tear)
which fracture is pathognomic of ACL injiry
Segond fracture- bony avulsion of the lateral proximal tibia
immediate management of ACL tear
RICE
rest
ice
compression
elevation
conservative management of ACL tear
- rehabilitation- strengthening of quadriceps to stabilise the knee
- cricket pad knee splint for comfort
surgical management of ACL tear
- reconstruction of ACL using a tendon or artificial graft
- not performed acutely
- months of physio before
- Acute surgical repair of ACL (only possible in some cases)
- GA knee arthroscopy, proceeding to an acute repair
- suturing ends of torn ligament together
complication of ACL tear
post truamatic OA
posteiror cruciate ligament tear
less common
role of PCL
the PCL is the primary restraint to posterior tibial translation and works to prevent hyperflexion of the knee.
PCL tear mechanism of injury
high energy trauma
proximal blow tot he tibia during a RTA
presentation of PCL
- immediate posterior knee pain
- instability of the joint
special test for PCL
positive posterior draw test (with a posterior sag) on examination.
investigations for PCL tear
As with ACL tears, the gold-standard for diagnosis for PCL tears is via MRI scanning.
management of PCL tear
conservatively
- brace
- physio
if symptomatic and recurrent instability → surgery with insertion of a graft