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
medial collateral ligament is the
most commonly injured ligament of the knee
role of the MCL
valgus stabiliser
MCL injury mechanism of injury
VALGUS trauma
direct impact to the outside of the knee
MCL injury grading
- Grade I – mild injury, with minimally torn fibres and no loss of MCL integrity
- Grade II – moderate injury, with an incomplete tear and increased laxity of the MCL
- Grade III – severe injury, with a complete tear and gross laxity of the MCL
presentation of MCL tear
- patient may report hearing a pop
- immediate medial joint line pain
- swelling starts a few hours after
- increased laxity when testing the MCL
- pt may be able to weight bear
special test for MCL
valgus stress test
- will have increased laxity
investigations for MCL tear
x-ray to exclude fracture
MRI= gold standard
The management of an MCL injury
is dependent on the grade of injury:
- Grade I Injury: Rest, Ice, Compression, and Elevation (RICE) with analgesia (typically NSAIDs) as the mainstay. Strength training as tolerated should be incorporated, with an aim to return to full exercise within around 6 weeks.
- Grade II Injury: Analgesia with a knee brace and weight-bearing/strength training as tolerated. Patients should aim to be able to return to full exercise within around 10 weeks
- Grade III Injury: Analgesia with a knee brace and crutches, however any associated distal avulsion then surgery is considered. Patients should aim to be able to return to full exercise within around 12 weeks.
The main complications following a MCL tear
are instability in the joint and damage to the saphenous nerve.
main investigations for ligaments of the knee
MRI is gold standard
you do an X-ray to check for fractures
Meniscal tears
Meniscal tears refer to damage of the menisci (the C-shaped fibrocartilage found in the knee joint). The menisci rest on the tibial plateau and have two main functions (1) shock-absorbers of the knee joint (2) increase articulating surface area.
difference between medial and lateral meniscus
The medial meniscus is less circular than the lateral and is attached to the medial collateral ligament,
The lateral meniscus is not attached to the lateral collateral ligament.
cause of meniscal teats
trauma-related injury and degenerative disease (the latter more common in older patients).
traumatic tears
- young patients who has twisted their knee whilst it is flexed and weight bearing
types of meniscal tear
- Vertical
- Longitudinal(Bucket-Handle)- most common
- Transverse(Parrot-Beak)
- Degenerative
presentation of meniscal tear
- tearing sensation
- intense sudden onset pain
- swells slowly
- may be lcoke din flexion and unable to extend
- joint line tenderness
- significant joint effusion
- limited knee flexion
special tests for meniscal tear
McMurray’s Test* and Apley’s Grind Test*
Apley test
The Apley distraction test is performed by pulling the leg toward the ceiling, while adding internal or external rotation. This test assesses for dysfunction of a collateral ligament. Laxity or pain in the joint indicates a positive test. This test can help determine which side is affected, but should be used in conjunction with other tests.
The Apley compression test is performed by exerting a downward pressure on the heel toward the knee, while adding internal or external rotation. This test assesses for dysfunction (e.g., tear) of a meniscus. Clicking or pain in the joint indicates a positive test. This test can help determine which side is affected, but should be used in conjunction with other tests.
McMurrays test
With the patient lying supine, flex the hip to 60–90º and flex their knee to 90º. Gently grasp the knee with one hand and their heel with your other hand.
Externally rotate the tibia, exert a valgus stress on the medial joint line, and finish with extension of the knee. This assesses for dysfunction of the medial meniscus.
Internally rotate the tibia, exert a varus stress on the lateral joint line, and finish with extension of the knee. This assesses for dysfunction of the lateral meniscus.
Pain or clicking indicates a positive test.
investigation for meniscal tear
X-ray to exclude fracure
MRI scan gold standard to confirm tear
management of smaller meniscal tears <1cm
RICE
management of larger meniscal tears
For larger tears or those remaining symptomatic, arthroscopic surgery is indicated:
- If the tear is in the outer third of the meniscus (where it has a rich vascular supply), then the tear can often be repaired using sutures
- If the tear is in the inner third, then the tear is usually trimmed to reduce locking symptoms (and middle third tears may either be repaired or trimmed)
complications of knee arthroscopy
- DVT
- damage to saphenous nerve and vein
- peroneal nerve
- popliteal vessel
RF for patella fracture
20-50 yo men
patella fracture mechanism of injury
- direct trauma to the patella
- rapid eccentric contraction of the quadriceps muscle (less common)
attachments of the patella
largest sesamoid bone in the body, formed within the tendon of the quadriceps femoris muscle as it crosses over the anterior aspect of the knee joint, attaching to the patellar ligament inferiorly. Its posterior surface consists of medial and lateral facets that articulate with their respective femoral condyles
presentation of patella fracture
- anterior knee pain
- pain worse with movement
- unable to straighten leg
- may not weight bear
- swelling and bruising
- visible and palpable patellar defect
what may be mistaken for a patella fracture
Bipartite Patella
Bipartite patella is a congenital condition affecting 2-3% of the population (more common in males), whereby there is failure of patella fusion, leaving two separate bone fragments of the patella joined only by fibrocartilaginous tissue.
The condition is typically asymptomatic and usually only picked up incidentally on imaging. Rarely, bipartite patella can present symptomatically, especially after exercise or overuse, with anterior knee pain.
investigations for patella fracture
x-ray (AP, lateral and syline)
CT indicated in comminuted fracture
conservative management of patella fracture
in cases of non-displaced or minimally displaced patella fractures, or with vertical fractures providing that the extensor mechanism remains functional.
- brace or cylinder cast,
- ensuring early weight bearing in extension with initial minimal displacement and articular step-off, before increasing flexion incrementally.
surgical managemnt of patella fracture
signif displacement or compromise to extensor mechanism
- open reduction and internal fixation (ORIF) with tension band wiring
This aims to convert the tensile force applied to the patella via the extensor mechanism into a compression force to assist with fracture reduction and healing.
In cases of simple vertical or transverse fractures occurring in the context of healthy cancellous bone, screw fixation can be used without the use of wires. In rare cases when ORIF is not possible, partial or total patellectomy may be considered.
