Knee pathologies Flashcards
Meniscal tears - What are menisci?
C shaped discs of fibrocartilage which only have a blood supply at the periphery
Look triangular on MRI (bowtie appearance)
Acts as a cushion between the femur and tibia
Shock absorbers
Meniscal tears - which menisci (MEDIAL/LATERAL) is more likely to be torn?
Medial
- as it is fixed and less mobile than the lateral meniscus
- as the knee pivots more on the medial meniscus
Meniscal tears - definition
Rupture of the menisci
Meniscal tears - causes
Sporting injury
Getting up from a squat
Meniscal tears - mechanism of injury
Twisting or turning quickly often while the foot is planted with the knee bent
Meniscal tears - clinical features
Very localised pain (usually at medial joint line)
Sudden pain
Sharp pain
Locking sensation (patient can’t fully extend the knee)
Meniscal tears - examination
Effusion (collection of fluid) develops by the next day
Joint line tenderness
Steinmann’s test
Meniscal tears - investigations
MRI (to confirm clinical suspicion)
Meniscal tears - management
Limited healing ability as they only have a peripheral blood supply
RICE
Physio
Consider arthroscopic meniscectomy for mechanical symptoms for irreparable tears / failed meniscal repair
Meniscal tears - radial tear
Shouldn’t be painful
Won’t heal
Meniscal tears - bucket handle tear
Meniscal tear flips out of normal position and physically jams in the knee. This prevents the knee from going straight, limits extension so the patient suddenly can’t fully extend the knee. This results in true knee locking
Meniscal tears - acute
Sport injury due to twisting
Meniscal tears - chronic
Degenerative tear due meniscus weakening with age
Collateral ligaments (2)
Medial collateral ligament (MCL)
Lateral collateral ligament (LCL)
MCL - function
Connects the bottom of the femur to the top of the tibia
Resists valgus stress - ie stops the knee from getting excessively knock kneed
MCL - causes
Contact sports
MCL - mechanism of injury
Direct ‘hit’ to the outer aspect of the knee which stretches/tears the MCL
Rupture results in valgus instability
MCL injury - clinical features
‘Popping’ sound upon injury
Pain and tenderness along the inner aspect of the knee
Swelling
Locking/catching of the knee joint
MCL injury - examination
Assess for joint effusion
MCL injury - investigations
MRI scan
MCL - management
Has a good blood supply so heals well RICE Early motion Physio Put leg in brace
LCL - function
Runs along the outside of the knee joint between the bottom of the femur and the top of the tibia.
Resists varus stress - ie stops excessive bow-leggedness
LCL - mechanism of injury
Direct force trauma to the inside of the knee. This puts pressure on the outside of the knee and results in various stress
High incidence of common fibular nerve injury
LCL injury - clinical features
Swelling of the outer aspect of the knee
Stiffness (locking)
Pain
LCL injury - examination
Effusion
LCL injury - investigations
MRI scan
LCL - management
Doesn’t heal well
A rupture needs urgent surgical repair
Cruciate ligaments (2)
Anterior (ACL)
Posterior (PCL)
ACL - function
Prevents abnormal internal rotation of the tibia, stops the tibia from rotating too much
ACL rupture - cause
High impact sports injury
ACL rupture - mechanism of injury
Twisting/turning the upper body laterally on a planted foot which causes the knee to give way.
May lead to rotatory instability
ACL rupture - clinical features
'Popping' sound Generalised deep pain all over knee Unable to continue activity Knee gives way on turning Can't weight bear
ACL rupture - examination
Bloody swelling accumulates in an hour (haemarthrosis)
Anterior drawer test
Lachman’s test
- excessive anterior translation of the tibia
ACL rupture - management
RICE
Physio
Analgesia
Reconstruct ACL (surgery - carried out for instability, not pain)
*Reconstruction is carried out if the patient is involved in intense sports
ACL rupture - prognosis
High risk of developing OA In later life
1/3 have no instability
1/3 can cope with instability
1/3 can’t cope with instability and want to het back to high impact sport
PCL - function
Resists posterior subluxation of the tibia
Prevents hyperextension and anterior translation of the femur
PCL rupture - cause
Direct blow to the anterior tibia whilst knee is flexed
motorbike crash, dashboard from crash
PCL rupture - mechanism of injury
Direct blow to the anterior tibia on a flexed knee
Hyperextension of the knee
Posterior subluxation of the tibia
PCL rupture - clinical features
Instability
Pain
PCL rupture - examination
Posterior sag of the tibia (as the femur rides over the tibia) Swelling
Brusing in the popliteal fossa
PCL rupture - management
If PCL is affected alone (unlikely) - no reconstruction
If other ligaments are affected - reconstruction required
Knee dislocation - definition
Rupture of at least 3 of the knee ligaments
Knee dislocation - cause
anterior, posterior, lateral
Anterior - severe hyperextension forces
Posterior - high energy injury (dashboard injury)
Lateral - rotational injury
Knee dislocation - clinical features
Immobility
Swelling
Gross deformity
Knee pain
Knee dislocation - examinations
Assess ACL, PCL, MCL, LCL
Knee dislocation - investigations
X-ray
MRI
Knee dislocation - management
Emergency reduction
Re-assess neuromuscular status
Confirm reduction (by doing a repeat X-ray)
Operative: ligament reconstruction
The patella always dislocates medially/laterally?
Laterally
Patella dislocation - who gets it
Females
Adolescence
Patella dislocation - risk factors
Ligamentous laxity
Genu valgum
Patella dislocation - clinical features
Obvious deformity
Patella dislocated laterally
Patella dislocation - examinations
May get a lipo-haemarthrosis
Patella dislocation - management
Reduction
Splint
Physio
Knee replacement - who gets it
Older patients
- where conservative management is no longer effective
Knee replacement - younger patients
Avoid young, active patients
Higher likelihood of failure
Likely to require revision surgery which is less effective
Extensor mechanism rupture - constituents
Patella Tibial tuberosity Patellar tendon Quadraceps tendon Quadriceps muscle
Extensor mechanism rupture - younger patients
Patellar tendon rupture
Extensor mechanism rupture - older patients
Quadriceps tendon rupture
Extensor mechanism rupture - predisposing factors
Chronic steroid use
Quinolone antibiotics
Diabetes
Hx tendonitis
Extensor mechanism rupture - examination
Unable to straight leg raise
Obvious palpable gap
Extensor mechanism rupture - investigations
X-ray
Extensor mechanism rupture - management
Tendon-tendon surgical repair
Reattachment of tendon to patella
Osteochondritis dissecans - definition
Lack of blood supply to an area of bone causes it to break off from the main bone
Osteichondritis dissecans - who gets it
Adolescents
Osgood schlatters disease - definition
Inflammation in the tibial tuberosity
Osgood schlatters disease - cause
Active adolescent boys
Growth spurts
Osgood schlatters disease - clinical features
Pain at tibial tuberosity
Bakers cyst - definition
Out pouching of the fluid that forms a lump behind the knee
Bakers cyst - management
Nothing
Septic arthritis - definition
Inflammation of the joint space caused by infection
Septic arthritis - causative organism
Staph aureus
Septic arthritis - clinical features
Similar to gout
- red hot, swollen, painful joint
Usually only one joint is affected
Septic arthritis - investigations
Joint aspirate
- if frank pus is aspirated then septic arthritis is diagnosis
X-ray
- pus fills joint space
Septic arthritis - management
Debridement of pus and fluid
Once causative organism is confirmed….
IV antibiotics
