Cortex- Lower Limb: Knee Flashcards
what are the compartments of the knee joint
medial and lateral compartments of the tibiofemoral joint
and the patellar joint
which part of the knee has the thickest hyaline cartilage in the body
retropatellar surface- reflection of the load placed on the patella
where are the menisci
tibiofemoral joint
what material are the menisci
fibrocartilage
what is the role of the menisci
ensure congruence between the concave femoral condyles and the flattish tibial plateau
shock absorbers
lubricate joint
what is the principle role of the ACL
prevent abnormal internal rotation of the tibia
what does the PCL prevent
hyperextension and anterior translation of the femur
what does the LCL resist
varus force and abnormal external rotation of the tibia
what can can predispose the knee to early OA
previous meniscal tears, ligament injuries (ACL deficiency) and malalignment (genum varum= medial OA, genum valgum= lateral OA)
what can influence primary knee OA
genetic influences, hobbies (football, distance running), occupation
what can predispose to the development of patellofemoral OA
patellofemoral dysfunction and instability
when can knee replacement be considered
in a patient with substantial pain and disability, where conservative management in no longer effective
what are the types of knee replacement
total (resurface all 3 components) or partial (unicompartmental knee replacement or patellofemoral replacement)
what is there less and extra risk of with TKR (when compared to THR)
less risk of dislocation
higher chance of unexplained pain (reliance upon the tension of soft tissues around the knee)
why is revision knee replacement a bigger surgery
often requires use of stems and a more hinged type of knee implant
when do meniscal injuries classically occur
with a twisting force on a loaded knee
what is the presentation of a meniscal injury
pain in medial (majority) or lateral joint line
effusion develops next day
mechanical symptoms- catching/ locking sensation (difficulty straightening knee with a 15 degree or so block to full extension)
may feel like knee is about to give way when walking is loose meniscal fragment caught in the knee
what causes true knee blocking (the mechanical block to full extension)
significantly torn meniscus flipping over and becoming stuck in the joint line associated with meniscal tears
can you have a meniscal tear without locking
yes
what is psuedo locking of the knee
temporary difficulty in straightening the joint (seen in other knee pathologies such as arthritis)
what typically causes an ACL rupture
a higher rotational force (turning the upper body laterally on a planted foot causing internal force on the tibia
what is the typical presentation of an ACL rupture
pop felt/ heard
development of a haemarthosis (effusion due to bleeding int he joint- vasculature of ACL) within an hour of injury
deep pain in the knee
patient will complain of rotatory instability with their knee giving way when turning on a planted foot (due to excessive internal rotation of the tibia)
what is typically caused by a valgus stress injury
torn medial collateral ligament (also potentially ACL and risking tibial plateau fracture)
what might a direct blow to the anterior tibia cause when knee flexed
rupture PCL due to hyperextension
what might a varus stress injury cause
rupture LCL (+/- PCL)
what can help delineate the extent of ligament injury
early MRI (only if exam difficult/ injury significant/ multiple ligaments injured)
what other tear is commonly seen with a meniscal tear
ACL tear
which might be found on clinical exam of a meniscal tear
effusion,
joint line tenderness,
pain on tibial rotation localised to the affected compartment (steinmann’s),
locked knee (displaced bucket handle tear) (15 degree springy block o full extension)
what is more common a medial or lateral mensical tear - why
medial (10 times)
as medial more fixed, less mobile
what are the patterns of meniscal tears
longitudinal, radial, oblique, horizontal
bucket handle tears- large longitudinal tear
where does the fragment of meniscus lodge to lock knee
into intercondylar notch
what causes a degenerative meniscal tear
meniscus weakens with age
can tear spontaneously or with a seemingly innocuous injury
first stage in many cause of knee OA
what are the patterns seen in degenerative meniscal tears
complex- horizontal, longitudinal and radial components
will degenerative tears be steinmanns positive
no
why does the meniscus have limited healing potential
as only has blood supply in its outer third
healing potential decreases with age and with increased time from injury
what is the surgical treatment for meniscal tears and who should get it
reasonable fresh longitundinal tears involving the outer 3rd in a younger patient (90% of tears not suitable)
meniscal repair- suturing the meniscus to its bed
if meniscus doesnt heal then do symptoms go away?
yes, pain and inflammation settle with time
knee will smooth off its own meniscus in time
what might help degernative meniscal tear’s early symptoms
steroid injection
what is the treatment for acute meniscal tears whos symptoms do not settle in 3 months
arthroscopic partial menisectomy
why is a meniscetomy not helpful in knees with degenerative change
as removal of menisci material will put more stress on already worn surfaces
what is the principle complaint of ACL deficiency
rotator instability with giving way on turning
what will you see on examination of an ACL rupture
knee swelling (haemarthrosis or effusion) excessive anterior translation of the tibia on the anterior drawer test and lachmans tests
what is the ACL rule of thirds
1/3rd of patients will compensate well and do whatever they please (inc sports)
1/3rd will manage by avoiding certain movements, may not be able to do high impact sports
1/3rd will do poorly with frequent giving way even with normal daily activities
why is primary repair of the torn ACL not often done
as is not effective and 40% will fail and need a reconstruction
who gets ACL reconstruction as there first treatment
professional sport players
those who’s knees give way on sedentary activity
those who want to get back into high impact sport but cannot do so despite physiotherapy
describe the process of ACL reconstruction
tendon graft, usually patellar, semitendinosis and gracilis autograft
is passed through tibial and femoral tunnels at the usual location of the ACL in the knee and secured to the bone
how long usually after an ACL reconstruction until the patient can return to high impact sports
a year with intensive rehabilitation
when in PCL reconstruction usually done
when there is multiple ligament injury
or if severe laxity and recurrent instability with frequent hyperextension or feeling unstable descending stairs (with anterior subluxation of the femur)
what tendon is used in a PCL reconstruction
cadaveric achilles tendon allograft
do MCL injuries heal
yes- majority of MCL partial and complete tears are expected to heal with little or no instability
what what is the presentation of an MCL tear
laxity and pain on valgus stress with tenderness over the origin or insertion of the MCL
how are acute MCL tears treated
hinged knee brace
how can chronic MCL instability be treated
with MCL tightening (advancement) or reconstruction with tendon graft
what is the treatment for an LCL tear
usually surgical with early repair or late construction with tendon graft
what is the sign of an LCL tear
instability on rotational movement- excessive rotation of the tibia and varus
what gives rise to an LCL injury
hyperextension and varus
what ligaments are affected in a complete knee dislocation
all four knee ligaments rupture
what is there high incidence of in complete knee dislocation
neurovascular injury
what is the treatment for a complete knee dislocation
reduced as an emergency
may require external fixation for temporary stabilisation
what is the important of an intimal tear in a knee dislocation
can later thrombose- regularly checks of the circulation of the foot mandatory
what should be done if there is concern with the distal circulation
vascular surgery assessment
vascular stenting or by-pass nay be required
what can happen in hyperfusion of the knee joint
compartment syndrome, especially after prolonged ischaemia- fasciotomies may be required
what treatment is usually required in combined knee ligament ruptures and knee dislocarions
multiple ligament reconstruction
when do osteochondral and chondral injuries occur
impaction or shear force of the articular surfaces/ due to a direct blow
how should osteochondral injuries bone be treated
pinning fragments of bone if large
if small removed arthroscopically
what makes up the extensor mechanism of the knee
tibial tuberosity, patellar tendon, quadriceps tendon and the quadriceps muscles
what can cause a patellar or quadriceps tendon rupture
lifting a heavy weight,
a fall,
spontaneously in a severely degenerate tendon
what age groups get either a ruptured patella or quadriceps tendon
patellar <40s
Quads >40s
what can predispose to an extensor mechanism rupture
history of tendonitis, chronic steroid use/ abuse (body builders), diabetes, RA, chronic renal failure
what antibiotic can cause tendonitis and risk tendon rupture
quinolone (ciprofloxacin)
do you give steroid injections for tendonitis of the extensor mechanism of the knee
no- high risk of tendon rupture
NEVER INJECT A TENDON WITH STEROID
what should be included in the assessment for all acute knee injuries
straight leg raise- to determine if the extensor mechanism is intact
what is a palpable sign of extensor mechanism rupture- what is seen of this on x rays
a palpable gap in the extensor mechanism
x ray will shoe a high (PT) or low (quads) patella
what might reduced extensor mechanism power suggest
a partial tear
what is the treatment for extensor mechanism ruptures
(for both complete and partial tears)
surgery- tendon to tendon repair or attachment of the tendon to the patella
what is patellofemoral dysfunction
disorder of the patellofemoral articulation resulting in anterior knee pain
what does ‘patellofemoral dysfuction’ encompass (3)
chondromalacia patellae (softening of the hyaline cartilage) adolescent anterior knee pain lateral patellar compression syndrome
in patellofemoral dysfunction what side of the knee is affected
lateral (as quads pull patellar to the side-plus is more common in females as wider hips= more lateral pull)
why is anterior knee pain seen in adolescents
ligamentous laxity
what are other predisposing factors for patellofemoral dysfunction
hypermobility, genu valgum, femoral neck anteversion
what is the presentation of patellofemoral dysfunction
anterior knee pain, worse going downhill, a grinding or clicking sensation at the front of the knee, stiffness after prolonged sitting (psuedolocking)
what is the treatment for patellofemoral dysfunction
90% will improve with physio
taping may alleviate the symptoms
surgery last resort
what can cause patellar dislocation
with a direct blow or sudden twist of the knee
what direction does the patella almost always dislocate
laterally
can the patellar spontaneously reduce
yes when knee straightened
what can happen to the surrounding structures when the patellar dislocates
the medial patellofemoral ligament tears
osteochondral fracture may occur (as the medial facet of the patella strikes the lateral femoral condyle)
what type of effusion is seen in a patellar dislocation
lipo-haemarthrosis (medial patellofemoral ligament tear)
what are the predisposing factors for a patellar dislocation
ligamentous laxity, female gender, shallow trochlear groove, genu valgum, femoral neck anteversion, high riding patella (patella alta)
what can decrease the risk of patellar instability
risk of recurrent instability decreases with age and physiotherapy
