Knee Problems + Trauma Flashcards
what type of joint is the knee
synovial joint
what type of cartilage covers the surfaces of the knee joint
hyaline cartilage
- retropatellar thickest cartilage in body
what is the function of the menisci in the knee
“shock absorbers” - act to distribute load evenly
what 4 ligaments are in the knee
Anterior + posterior cruciate ligaments
Medial + lateral collateral ligaments
what is the function of the ACL
ACL prevents abnormal internal rotation
what is the function of the PCL
PCL prevents hyperextension
what is the function of the MCL
MCL resists valgus force
what is the function of the LCL
LCL resits varus force
what problems in the knee may result in early OA
Meniscal tears
ACL rupture
Malaligment
what side of the knee is affected by OA in genu varum
medial OA
what side of the knee is affected by OA in genu valgum
lateral OA
what treatment can help young patients with isolated medial compartment OA
osteotomy of proximal tibia
- bone cut for re-aligment
- shifts load to lateral compartment
when should total knee replacements be considered
substantial pain + disability where conservative measures are no longer effective
meniscal injuries classically occur due to what
twisting force on a loaded knee
presentation of a meniscal injury
localising pain to medial / lateral joint line
effusion
knee locking - difficulty straightening leg
feeling of knee giving way
which meniscus is more commonly injured
medial
- it is more fixed + less mobile than the lateral
what causes true knee locking
mechanical block to full extension caused by torn meniscus becoming stuck in the joint line
what is pseudo-knee locking
occurs in OA
knee joint becomes temporarily stuck with difficulty straightening
resolves spontaneously or patient will have developed trick to relieve the issue
how do ACL ruptures occur
twisting injury- high rotational force
presentation of ACL rupture
“pop” may be felt/ heard
haemarthrosis within 1 hour
deep pain
rotatory instability
how do MCL ruptures occur
from a Valgus stress
e.g. rugby tackle from side
how do PCL ruptures occur
“dashboard injury”
- direct blow to anterior tibia with knee flexed
what is Steinmanns test
+ve in acute meniscal tears (young patients, high energy injury)
- pain on tibial rotation localising to the affected compartment
meniscal tears are often related to what other injury
ACL rupture
what is a bucket handle meniscal tear
large longitudinal tear flips out of normal position and becomes stuck in intercondylr notch
– locking of knee
what is a degenerate meniscal tear?
what condition is it a sign of?
spontaneous tear / due to innocuous injury
sign of OA
Steinmanns test will be negative
why do meniscal injuries have limited healing potential
only have blood supply to outer 1/3rd
healing potential decreases with age
hallmarks of ACL rupture on examination
rotatory instability with giving way on turning
+ve Lachmans test
excessive anterior translation of the tibia on anterior drawer test
what is important in treatment of ACL rupture
pysio!!
- same results as surgical reconstruction
treatment of PCL rupture
conservative management
- only those with severe laxity / recurrent instability / frequent hyperextension will be considered for surgery
how are MCL ruptures treated?
how well do they heal?
hinged knee brace
heal well - instability uncommon
what other surrounding structures may also be damaged in an LCL tear
common peroneal nerve
popliteal artery
a complete knee dislocation results from a rupture of what
rupture of all 4 ligament
- required surgery due to degree of instability
what constitutes the extensor mechanism of the knee
tibial tuberosity
patellar tendon
quadriceps tendon
quadriceps muscle
how is the extensor mechanism tested
ability to perform straight leg raise = intact
how is the extensor mechanism injured
rapid contractile force
e.g. after lifting heavy weight
what antibiotics can increase risk of tendon rupture
quinolones
what other things increase risk of extensor mechanism rupture
tendonitis chronic steroid use RA CKD Diabetes
why should steroid injections be avoided in treatment of extensor mechanism ruptures
high risk of tendon rupture
on Xray what would the following suggest
- high lying patella
- low lying patella
high lying - patella tendon rupture
low lying - quadriceps tendon rupture
symptoms of patellofemoral dysfunction
anterior knee pain (worse going downhill)
grinding/clicking at front of knee
pseudolocking after long periods of inactivity
treatment of patellofemoral dysfunction
pysiotherapy - particularly strengthening vastus medalis
taping may alleviate symptoms
what might cause a patellar dislocation
direct blow
sudden twisting of knee
what patients get distal femoral fractures? how do they occur?
osteoporotic bone - fall onto flexed knee
why will a distal femoral fracture adopt a flexed position
pull from gastrocnemius muscle
treatment of distal femoral fracture
fixed with plate + screws
why is a complete knee dislocation a surgical emergency
high risk of vascular injury + nerve damage
high risk of compartment syndrome
what type of fracture are tibial plateu fractures
intra-articular
- classified by schatzker system
what nerve might be damaged in a medial tibial plateau fracture? what is the clinical sign?
common peroneal nerve – Foot drop
treatment of tibial plateu fracture
open reduction internal fixation
