Knee Flashcards
Name the two ‘joints’ that make up the knee joint.
- Medial and lateral compartments of the tibiofemoral joint
- Patellofemoral joint
What is the role of the menisci in the tibiofemoral joint
- Ensures congruence of the concave femoral condoles & flattish tibial plateau
- Act as shock absorbers
What is the main role of the ACL & how is it tested
Main role: Resists internal rotation of tibia,
But also: Prevents anterior translation of tibia
Clinical test: Lachman’s/ Anterior drawer test
What is the main roles of PCL & how is it tested
Main roles: Prevents hyperextension & posterior translation of tibia
Clinical Test: Posterior drawer test
What is the main roles of MCL
Resists valgus force
What is the main roles of LCL
Resists varus force & external rotation of tibia
Clinical history & presentation of an ACL tear
- High force twisting injury with audible ‘pop’
- Sudden onset rotatory instability
- Positive anterior drawer/ lachman’s test
- Haemarthrosis effusion within an hour
Clinical history & presentation of a PCL tear
- Direct blow to anterior tibia
- Hyper extension &/ instability descending stairs
- Positive posterior drawer test
Clinical history & management of an MCL tear
- Valgus stress
- Medial joint line tenderness
Clinical history & management of an LCL tear
- Varus stress
- Lateral joint line tenderness
- Associated ACL/PCL tear
Clinical history of a menisceal tear
- Twisting injury on loaded knee OR
- getting up from squatting
- ‘giving way’/ ‘catching’/ ‘locking’
Clinical presentation of a lateral menisceal tear
- pain on internal rotation
- pain on lateral joint line
- effusion within a day
- ‘catching’/ ‘locking’ when straightening knee
Clinical presentation of a medial menisceal tear
- pain on external rotation
- pain on medial joint line
- effusion within a day
- ‘catching’/ ‘locking’ when straightening knee
If you were to take a joint aspiration after a ligament tear what would you expect to find?
Haemarthrosis (especially with ACL tears)
What nerve is commonly injury with an LCL tear
Common peroneal nerve injury
What clinical test can be used to check for a menisceal tear
Steinman’s/ McMurrays test
Summarise the clinical tests used for ACL, PCL, MCl & LCL tears
ACL - anterior drawer test/ lachmans test
PCL - posterior drawer test
MCL - valgus stress test
LCL - varus stress test
How would you test for a displaced bucket handle menisceal tear
Heel height test
Positive - heel height discrepancy, indicating fixed flexion deformity
How would you test for a bucket handle menisceal tear
Heel height test
Positive - heel height discrepancy
Why might a patient feel as though their knee might give way with a menisceal tear
Loose menisceal fragment is caught in the knee when walking
Why might a patient feel as though their knee might give way with a menisceal tear
Loose menisceal fragment is caught in the knee when walking
Valgus stress injuries usually cause an MCL tear. If they occur at a high enough force, they can also tear another ligament and risk fracture of a bone. Name this ligament & bone.
ACL & tibial plateau fracture
What does a lipohaemarthrosis indicate
- Fracture with intra-articular extension OR
- significant intra-articulator soft tissue injury (ligament or menisci)
Degenerate menisceal tears occur with age and are often the first stage of what condition
Osteoarthritis
Why do meniscal tears have a limited healing potential
Menisci only have an arterial blood supply around their outer third
What two factors further decrease the healing potential of meniscal tears
- age >25yrs
- increased time from injury
Meniscal tear investigations
MRI
Meniscal tear management
Young patient & bucket handle meniscal tear OR
Younger patient & acute traumatic peripheral meniscal tear
=> possibility for meniscal repair
————————————————————————————
Failed meniscal repair & recurrent pain/locking/effusion OR
Meniscal repair unsuitable & recurrent pain/locking/effusion
=> arthroscopic meniscectomy
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If degenerative changes on X-ray or MRI
=> avoid surgical intervention
=> analgesia & possible corticosteroid injections
ACL/PCL/MCL/LCL Investigations
Usually clinical diagnosis but MRI can be helpful for confirmation or to rule out other conditions.
Summarise ACL/PCL/MCL/LCL treatment
- Acute MCL tear - hinged knee brace
- Chronic MCL tear - MCL tightening
———————————————————————————— - Acute LCL tear - Repair
- Late diagnosis - Reconstruction with tendon graft
———————————————————————————— - Acute ACL/PCL tear - Rest & physio
- Chronic ACL/PCL instability - Reconstruction & rehab
Name some factors that make someone a good candidate for ACL reconstruction
- failure to respond to physio
- professional sportsperson
- those whose knees give way on sedentary activities
What does an ACL reconstruction involve
Tendon graft being passed through tibial and femoral tunnels and secured at usual ACL location. Followed by intensive rehab with up to a year before getting back to high impact sports.
Complete knee dislocation aetiology
- serious high energy injuries OR
- low energy injuries in elderly
Complete knee dislocation investigations
- Urgent & then regular neurovascular status checks
- Imaging - NV status concern (CT angio), no concern (MRI)
Complete knee dislocation management
IMMEDIATE
- Urgent neurovascular status check
- Emergency reduction under sedation & external fixator PRN
- Recheck neurovascular status
————————————————————————————
IF VASCULAR ISSUE
- Vascular stenting or bypass
- Observe closely for compartment syndrome
————————————————————————————
DEFINITIVE
- Multi-ligamentous repair
Which nerve & which artery is commonly affected in a complete knee dislocation
- Popliteal artery
- Common peroneal nerve
What makes up the extensor mechanism of the knee
Tibial tubersoity, patellar tendon, patella
Quadriceps tendon, quadriceps muscles
Extensor mechanism rupture clinical history
Rapid contractile force e.g. after heavy lifting, falling or severe tendon degeneration
Extensor mechanism rupture risk factors
- Runners or jumpers
- Previous tendonitis, Steroids, Quinolones
- CKD, Diabetes, RA
Extensor mechanism rupture can be caused by rupture of the patellar or quadriceps tendon. Which is more likely in younger patients and which is more likely in older patients?
Younger patients (<40) - Patellar tendon
Older patients (>40) - Quadriceps tendon
Extensor mechanism rupture clinical presentation
- Sudden onset knee pain and weakness
- Unable to straight leg raise (or reduced power - partial tear)
- Palpable gap in extensor mechanism
Extensor mechanism rupture investigations
- X-Ray - Effusion & patellar displacement (high -PT, low -QT)
- USS/MRI - Partial/ complete tendon tear
Extensor mechanism (complete/ substantial partial) rupture management
Urgent surgical repair and post-op physio
Can steroid injections be used in extensor mechanism tendonitis? Why?
No - high risk of rupture
What is patellofemoral dysfunction and how would it present?
What? - Any disorder of patellofemoral articulation causing anterior knee pain, often worse when going downhill.
Other symptoms - grinding or clicking sensation & pseudolocking/ stiffness after prolonged sitting
Patellofemoral dysfunction management
Physiotherapy to rebalance quadriceps muscles
(especially the vastus medialis obliqus)
Softening of the patella hyaline cartilage can occur in patellofemoral dysfunction. What is the name for it?
Chondromalacia patellae
Patellar dislocations can occur with a direct blow or sudden twist of the knee. Which way does the patellar tend to dislocate to? Which ligament is teared?
Laterally
Medial patellofemoral ligament tear
As the medial facet of the patella strikes the lateral femoral condyle during patella dislocation, what may occur?
Osteochondral fracture
Describe the X-ray appearance of a patellar dislocation
- Medial patellofemoral tear
- Lipohaemarthrosis
- Small opacification (if osteochondral fracture)
Patella dislocation management
Usually spontaneously reduces.
Follow up physiotherapy
Recurrent patella dislocation/ instability management
Patellofemoral ligament reconstruction + tendon autograft
OR Tibial tubercle transfer
Patella dislocation investigations
- Positive patella apprehension test
- X-ray
Patella dislocation risk factors
- Ligamentous laxity/hypermobility
- Increased Q-angle - genu valgum, femoral neck anteversion
- High riding patella
- Hypoplastic lateral femoral condyle
- Lateral quads insertions or weak vastus medialis
What is a major source of pain after a meniscal/ ligament injury & how is it treated
Bone marrow oedema
Self limiting, typically settles after 3 months
Loose bodies can occur due to trauma, OCD and joints degeneration and present as a mobile lump or sharp occasional pain & locking. How would you determine whether it is truly a ‘loose’ body or not?
MRI or serial XRay’s
A fabella is commonly misdiagnosed as a loose body on X-Ray. What is it?
An accessory ossicle usually in the lateral head of the gastrocnemius
acute haemarthrosis… what next?
acute haemarthrosis warrants an MRI to confirm Dx and look for associated injuries
acutely locked knee… what next?
acutely locked knee warrants prompt MRI and management to prevent fixed flexion and potentially repair a meniscus
Football injury, twist, pop, haemarthrosis, generalised pain, pain settles after a few days, rotatory instability. What is the most likely diagnosis?
ACL rupture
Getting up from squatting, sudden sharp pain medial joint line, effusion, recurrent medial pain & catching +/- locking. What is the most likely diagnosis?
Meniscal tear
