Knee Flashcards
where is the thickest hyaline cartilage in the body found
retropatellar surface
chondrocytes
chondrocytes live in ECM in lacuna
they secrete and maintain the ECM
what properties do collagen fibres and proteoglycans have
collagen fibres have tensile strength
proteoglycans are highly hydrophilic -act like balloons to give compressive stength
cartilage healing
only healing of full thickness injuries is possible - fibrocartilage forms
this is less wear resistant and has greater friction
cartilage regeneration surgical methods
drilling/microfracture - holes drilled to induce bleeding promoting fibrocartilage formation from stem cells differentiating into chondrocytes
osteochondral autograft or allograft
mosaicplasty
MACI
mosaicplasty
- Harvest small grafts from non-weight bearing regions of knee and transplant onto affected area
MACI
membrane induced autologous chondocyte implantation - harvest healthy chondrocytes
osteochondritis dissecans
subchondral bone becomes avascular, and may progress to fragments of bone breaking away to form loose bodies
pothole on surface of bone predisposes to OA
where/who does OD commonly affect
knee - lateral side of femoral head
adolescence
treatment of OD
may heal spontaneously
lesions which are at risk of breaking off are fixed and loss fragments removed
what predisposes one to early OA of the knee
previous meniscal tears, ligament injuries, malalginment
inflammatory arthritis
patellofemoral dysfunction and instability predipose to patellofemoral OA
what OA does genu varus and valgus predipose one to
varus - medial
valgus - lateral
who would receive an osteotomy to treat OA
younger patients with isolated medial compartment OA - particularly in varus knee - shift the load to the lateral compartment
heavy manual workers
results of osteotomy
unpredictable
benefit lasts around 7-10 years
can affect results of later TKR
when is knee replacement considered (OA)
patient with substantial pain and disability where conservative management is no longer effective
partial or total
results of knee replacement
dissapointing results for OA
younger patients have poorer outcomes
PKR poorer results than TKR (80% satisfaction, 20% ongoing pain)
when is unicompartmental knee replacement considered
potential treatment for patients with isolated OA
particularly younger patients
risks of KR surgery
infection, thrombosis
often unexplained knee pain after TKR
likely failure and revision surgery in younger patients
if the knee examination is difficult due to pain, but is thought to be significant what will be performed
MRI
when do meniscal tears classically occur
twisting force on loaded knee or when getting up from squatting
who do meniscal tears usually occur in
sporting injuries in younger patients
meniscal injury
twsting force/getting up from squatting
pain localises to medial/lateral joint line
effusion develops (inc synovial fluid)
pain and mechanical symptoms - catching/locking
what clinical examination will be performed in acute meniscal tear
steinmann’s test - pain on tibial rotation localising to affected compartment
what is found in the knee joint in meniscal tear
effusion - increased synovial fluid
what will confirm clinical suspicion of a meniscal tear
MRI
true knee locking
- mechanical block to full extension caused by torn meniscus flipping over and becoming stuck in joint line
- may require partial meniscectomy to unlock knee and prevent further damage
- can perform heel height test if suspected
what is true knee locking a clinical sign of
meniscal tear
- can occur without locking however
pseudlocking
can occur in patients with OA etc that describe their knee can temporarily become stuck when straightening the joint
are lateral or medial meniscal tears more common
medial as it is fixed (lateral is mobile)
types of meniscal tear
what is a large longitudinal meniscal tear called and what can it cause
bucket handle tear
- knee locking
degenerative meniscal tears
can occur as meniscus weakens with age - first stage in many knee OA
how are degenerative meniscal tears clinically distinguished from acute tears
Steinmann’s test negative
early signs and symptoms of OA likely
treatment of degenerative meniscal tears
will not improve from arthoscopic meniscectomy
steroid injection will help symptoms
meniscal repair
only the outer third has arterial blood supply - limited healing potential
red zone has highest chance of healing
Whilst meniscal tears don’t usually heal, the pain and inflammation may settle with time, particularly with degenerate tears.
when should arthroscopic meniscectomy be considered
in acute peripheral tears in young patients
grades of knee ligament injury
1- tear some fibres but macroscopic structure intact (sprain)
2 - some fascicles disrupted (partial tear)
3 - complete tear
MCL resists
valgus stress
LCL resists
varus stress
ACL resists
anterior subluxation of tibia and internal rotation of the tibia
PCL resists
posterior subluxation of the tibia and hyperextension at knee
posterolateral corner
PCL and LCL with popliteus etc resist external rotation of the tibia in flexion
MCL tear
valgus stress injury eg rugby tackle from side
usually heals well - patient may have laxity and pain of valgus stress
unhappy triad
MCL, ACL and medial meniscus
MCL treatment
acute - hinged knee brace
chronic - MCL tightening or reconstruction with tendon graft
usually heal well - some laxity and pain on valgus stress experienced
ACL tear
usually occur with a higher rotational force (internal rotational force on tibia)
pop is felt or heard
haemarthrosis (effusion due to bleeding in joint from ACL vascular supply) occurs
chronically, excessive internal rotation (instability)
ACL rupture - on examination
excessive anterior translation of tibia on ant drawer test and Lachmann test
ACL rule of thirds
third function well and compensate
third avoid instability by avoiding certain activities
third dont compensate and have frequent instability/cant go back to sport
repair
of ACL
primary repair is not effective
reconstruction available with tendon graft (from patellar, gracilis or semitendinosus)
only given to patients who need to get back to sport (eg professional) or those whose knees give way with sedentary activity
intensive rehabilitation required
who gets what treatment in ACL
older patients are more likely to compensate.avoid certain activities
younger patients more likely to get surgery
LCL tear
varus stress injury (+/- PCL)
LCL doesnt heal and causes varus and rotatory instability (excessive external rotation)
high incidence of common peroneal nerve palsy and other vascular injuries
often part of multiple knee ligament injury
LCL tear treatment
complete rupture needs early repair
late repair involves reconstruction
PCL tear
a direct blow to anterior tibia on flexed knee (dashboard/motorbike) or hyperextension
PCL instability may cause hyperextension, and feeling of unstable when going down stairs
knee dislocation
complete knee dislocation results in rupture of all 4 ligaments and has a high incidence of neurovascular injury
what neurovascular structures are commonly affected in knee dislocation
popliteal artery
common peroneal nerve (end branch of sciatic nerve)
compartment syndrome
treatment of knee dislocation
emergency reduction
may require external fixation for temporary stabilisation
usually multi ligament reconstruction is required
what is a particular risk of knee dislocation
intimal tears can thrombose - regular foot checks are mandatory
any concerns with vascular status require vascular surgery assessment
reperfusion may result in compartment syndrome
patellar dislocation
can occur with direct blow or sudden twist of knee
virtually always dislocates laterally
predisposition for patellar dislocation
inc incidence in females, teens, hypermobility, valgus knee and torsional abnormalities
risk dec with age and physio
recurrent dislocation - 10%
what is seen on x ray with patellar dislocation
lipohaemarthorsis
fat sits on top of blood
what is performed is there is frequent patellar dislocation
tibial tubercule transfer or medial patellofemoral ligament reconstruction
what is the extensor mechanism of knee
tibial tuberosity, patella, patellar tendon, quadriceps, quadriceps tendon
what tendon of extensor mechanisms tends to rupture
patellar <40
quadriceps > 40
how does extensor mechanisms rupture come about
falling onto flexed knee with quads contraction
predisposing factors for extensor mechanism rupture
history of tendonitis
chronic steroid abuse
diabetes
RA
chronic renal failure
quinolone antibiotics (ciprofloxacin)
how do quinolone antibiotics inc risk of EMR
can cause tendonitis
what should be avoided in tendonitis with possible EMR
steroid injections
examination of patient with EMR
unable to straight leg raise
paplable gap in extensor mechanism
X ray
in obese patients US can be used to view the gap in extensor mechanism
treatment of EMR
surgical tendon to tendon repair or reattachment of tendon to patella
what often occurs in patellofemoral dysfunction
chondromalacia patella (softening of hyaline cartilage of patella)
why are teens more likely to get patellofemoral dysfunction
inc ligamentous laxity
why are females more likely to get patellofemoral dysfunction
wider hips and subsequent more lateral pull of quadriceps
patellofemoral dysfunction presentation
anterior knee pain,worse down hill
grinding or clicking sensation
pseudolocking
patellofemoral dysfunction treatment
most cases self limiting and patients grow out of them
physiotherapy
pre patellar bursitis
- eg housemaids knee, carpet layers knee
- most likely due to repetitive knee trauma
- presents as severe anterior knee pain, warmth and swelling of the patella
- local pain on patellar presssure and pain with knee flexion
treatment of non septic bursitis
NSAIDs with the option of local steroid injection
treatment of septic arthritis
ABx cover and drainage
