Knee (Session 4) Flashcards
If the fracture completely splits the patella (extensor mechanims=disrupted) distal to insertion of quadriceps, what will the patient be unable to do?
Perform a straight leg raise
What is the usual mechanism of injury for pre-patella burisitis?
- Repetitive trauma
- Fall onto knee
- Blunt trauma
How will a patient present following a collateral ligament injury?
- Pain
- Swelling
- Unstable feeling
- Knee not supporting body weight
How does septic arthritis different from reactive arthritis?
- Reactive arthritis= Sterile inflammatory process (can result from extra-articular infection)
- Septic arthritis= Invasion of joint space by microorganisms
Which other ligament do the collateral ligaments work with to prevemt excessive posterior motion of the tibia on the femur?
PCL
Posterior cruciate ligament
What is the most common direction for the patella to dislocate and why?
Laterally
Due to Q angle of knee (line of pull of quadriceps tendon and patellar ligament)
What is the distinctive finding for an infection of a prosthetic joint (physical findings for this are often minimal)?
Draining sinus from underlying affected joint
What are the three types of possible swellings around the knee?
- Bony (Osgood-Schlatter’s disease)
- Soft tissue
- Localised- lymph node, popliteal artery aneurysm
- Lymphodema of lower limb
- Fluid
- Inside joint- effusion
- Outside joint- soft tissue haematoma
What are the 2 types of acute knee effusion?
- Haemarthrosis (ACL rupture until proven otherwise)
- Lipo-haemarthrosis (fracture until proven otherwise- fat release from bone marrow)
How are PCL injuries managed?
Conservatively:
- Bracing
- Rehabilitation
Name some symptoms of OA of the knee
- Crepitus
- Effusion
- Knee buckling/giving way (esp when going downstairs)
What is the usual mechanism of injury for a distal femoral shaft fracture in the elderly?
Fall from standing
After reduction of the knee joint following a knee dislocation, what needs to be carried out?
MRA
(Magnetic Resonance Angiography)
to fully asses vascularity of leg
What % of skeletal injuries do patella fractures account for?
1%
What does the following image show?
Effusion of left knee
Give some factors which predispose to patellar dislocation?
- Generalised ligamentous laxity
- Weak quadriceps
- Shallow trochlear
- Long patellar ligament
- Previous dislocations
How does a patient with a meniscal injury usually present?
Intermittent pain
Pain localised to joint line
Knee clicking, catching, locking
Sensation of giving way
Swelling (delayed as menisci largely avascular)
Chronic effusion (due to synovitis)
Why does a torn LCL have a higher chance of causing knee instability?
Medial tibial plateau- deeper and more stable socket for femoral condyle than laterl tibial plateau
What are the risk factors for developing septic arthritis?
- Extremes of age
- Diabetes mellitus
- Rheumatoid arthritis
- Immunosuppression
- IV drug use
Where does a knee effusion often present within the knee?
Suprapatellar bursa
= extension of synovial cavity of knee joint
What is the usual mechanism of injury for a tibial plateau fracture?
Axial loading with varus/valgus angulation of knee
How are patellar fractures treated? (displaced and undisplaced)
- Displaced:
- Reduction
- Surgical fixation
- Undisplaced:
- Protected- splinting, crutches
What pathogens cause septic arthiritis?
- Staphylococcus aureus
- Staph. epidermis
- Neisseria gonorrhoeae
- Strep. viridans
- Strep. pneumoniae
- Group B Streptococci
What does it mean if the OA of the knee is Tri-compartmental?
Arthritis affecting 3 compartments:
- Medial femorotibial
- Lateral femorotibial
- Patellofemoral
Which collateral ligament (of the knee) is torn more commonly (LCL or MCL)?
MCL
BUT torn LCL- higher chance of causing knee instability
How does a meniscal injury usually occur?
Sudden twisting motion of weight-bearing knee in high degree of flexion
What is the defined time for the development of an ‘acute effusion’?
<6 hours after injury
(Delayed= >6 hours after injury)
In acute varus strain, which ligament is at risk?
LCL
Lateral collateral ligament
How is OSD managed?
Usually resolved with ice and rest
Bony prominence usually remains permanently
What % of the population are affected by OA of the knee?
12%
(35% over 75 years)
How are femoral shaft fractures treated?
Surgical fixation
What is another name for pre-patellar bursitis?
Housemaid’s knee
Apart from the usual triad of symptoms, what other symptoms may someone with septic arthritis present with?
- Erythema
- Swelling
- Warmth
- Tenderness
- Limitation of active and passive range of motion
What is the most common joint affected by septic arthritis?
Knee (50%)
Other than a palpable defect in the patella, what other sign with a patient present with if they have experienced a patella fracture?
Haemarthrosis (blood in joint)
How many of the 4 ligaments must be ruptured in order to dislocate the knee?
at least 3/4
- MCL
- LCL
- ACL
- PCL
What is the usual mechanism of injury for a femoral shaft fracture in children/young adults?
High velocity trauma
(fall from height/road accident)
How many Total Knee replacements (TKR) are performed each year in the UK?
110,000
Why are prosthetic joints a risk factor for septic arthritis?
- Intraoperative contamination
- Haematogenous spread from distant infective focus
Polymethacrylate cement used- inhibits WBC and complement function
Delayed wound healing= major risk factor
Patient may become symptomatic months/years after inital operation
Why does a patient with a femoral shaft fracture have a risk of developing hypovolaemic shock?
Blood loss- closed femoral fracture: 1000=1500mL
Blood loss- open femoral fracture: may be double
What is shown in the following image?
Semimembranosus bursitis
Swelling in popliteal fossa- fluid forces its way out of joint and into bursa
What’s another name for infra-patella bursitis?
Clergyman’s knee
(Repeated microtrauma caused by kneeling)
How is a patella disloaction treated?
- Manually extending knee- reduce patella
- Immobilisation
- Physiotherapy
What are the 2 main mechanisms of injury for a patella fracture?
- Direct impact injury
- Eccentric contraction of quadriceps
What usually cause OSD?
Teenagers- playing sport- localised pain and swelling
(bilateral 20-30% of cases)
Which cruciate ligament is injured more commonly and why?
ACL as= weaker than PCL
In acute valgus strain, which ligament is at risk?
Medial collateral ligament
What is a bipartite patella?
Normal anatomical variant (8% of population)
Failure of union of secondary ossification centre
Often mistaken on x-rays for patella fracture
Which artery may become involved if there is significant displacement of the fracture in a distal femoral fracture?
Popliteal
What can be seen in the following image?
- Tibial plateau fracture
- Lipohaemarthrosis (arrow)
What may cause ‘delayed effusion’ of the knee?
Reactive synovitis
Response to injury- increased volume of synovial fluid
Name 3 types of deformities that may be caused by osteoarthirits at the knee joint?
- Varus deformity (see image)
- Valgus deformity
- Fixed flexion deformity (knee cannot fully extend)
What does this image show?
Tibial plateau fracture
(can be unicondylar/bicondylar)
(Lateral tibial condyle fractures=most common)
What is the most common cause of patella dislocation?
Trauma:
- Twisting injury in slight flexion
- Direct blow to knee
(Mostly affects athletic teenagers)
If a patient has torn their ACL, how do they usually present?
- Feels popping sensation in knee
- Immediate swelling
- Instability
- Rotational instability
What’s the difference between varus and valgus angulation?
Why do most patients develop a degree of post-traumatic osteoarthritis in the affected joint?
Articular cartilage = always damaged
What is Osgood-Schlatter’s disease? (OSD)
Inflammation of apophysis (site of insertion) of patella ligament into tibial tuberosity
What is the most common mechanism of a PCL injury?
Dashboard injury
Knee=flexed
Large force applied to upper tibia
- displacing posteriorly
What are the typical symptoms of knee osteoarthiritis? (3)
- Knee pain
- Stiffness
- Swelling
Are the following x-rays normal or abnormal?
Normal
Why causes a dislocation of the knee?
High energy trauma
What are the 2 management options for a torn ACL?
- Conservative- some patients can cope without ACL
- Sportsmen/active people- need surgical reconstruction
What is the mechanism of injury for the ‘unhappy triad’?
Strong force applied to knee
How does a patient with prepatellar bursitis usually present?
Knee pain
Swelling
What are the risk factors for OA?
- Age
- Female sex
- Previous trauma
- Obesity
- Family history of OA
- Another condition affecting joint
What tests are used to detect ACL/PCL injuries?
- Anterior and posterior draw tests
- Lachman’s test
How is the patella held in place?
Contraction of inferior fibres of vastus medialis
Stabilises patella within trochlear groove
Apart from post-traumatic osteoarthritis, what other complications are associated with tibial plateau fractures? (2)
- Meniscal tears
- ACL injuries
How will a patient with OSD present?
- Intense knee pain during:
- Running
- Jumping
- Squatting
- Ascending/descending stairs
- Kneeling
What are the 4 sites where pulses can be palpated in the lower limb?
- Femoral
- Popliteal
- Dorsalis
- Posterior tibial
What is the triad of symptoms which patients with septic arthritis usually present with?
- Fever (40-60%)
- Pain (75%0
- Reduced range of motion
(Symptoms may evolve over few days/weeks)
Which artery is likely to be injured as a result of knee dislocation?
Popliteal
(V. immobile- so high risk of it being injured)
Will either:
- tear: haematoma
- crushed: thrombotic occlusion
What does this xray show?
Distal femoral shaft fracture
How are meniscle tears treated?
- Acute: surgically- repair
- Chronic: conservative management
What should be done if septic arthritis is suspected?
Aspiration of joint immediately
Aspirate sent- urgent microscopy, culture, sensitivities
What age group do patella fractures most commonly occur in?
20-50yrs
Which bursae of the knee are most commonly inflamed?
- Prepatellar bursa
- Infrapatellar bursa
- Pes anserinus bursa
- Suprapatella bursa
How does the msuculature act as a deforming force in a femoral shaft fracture?
- Proximal fragment
- -abducted
- -gluteus maximus- greater trochanter
- -gluteus minimus
- -flexed
- ilopsoas- lesser trochanter
- -abducted
- Distal segment
- -adducted into varus deformity
- -adductor magnus
- -gracilis
- -extended
- pull of gastrocnemius
- -adducted into varus deformity
What usually causes injuries to the collateral ligaments of the knee?
Acute varus/valgus angulation of knee
What’s another name for Semimembranosus bursitis?
Baker’s cyst
Popliteal cyst
What are the mechanisms of injury for the anterior cruciate ligament?
- Quick deceleration
- Hyperextension
- Rotational injury
- Large force to back of knee with joint partially flexed
(Usually non-contact)
What conditions may suprapatellar bursitis be a sign of? (5)
- Osteoarthiritis
- Rheumatoid arthritis
- Infection (septic arthritis)
- Gout and pseudogout
- Repetitive microtrauma to the joint
What can cause a mechanical block to motion/locking in a displaced meniscal tear?
Loose meniscal fragments=trapped in articular surfaces
If a patient has a meniscal tear and they present with acute haemarthrosis, what does this it indicate?
- Tear in peripheral vascular aspect of meniscus
- Injury to ACL (Unhappy triad)
What is a major consequence of bacterial invasion (in the joint)?
Damages articular cartilage: Hydrolysis of collagen and proteoglycans
What’s the prognosis for septic arthritis?
High morbidity- even if treated optimally
50% adults have:
Decreased range of motion
Chronic pain
…even after infection is resolved
Why might a femoral shaft fracture be caused by a low velocity trauma in elderly patients/patients with bone metastasis?
Weaker bones
What is the unhappy triad? (‘Blown knee’)
Injury to:
- ACL
- MCL
- Medial meniscus (as firmly adhered MCL)
Describe the prepatellar bursa?
Superficial bursa (between skin and patella)
Thin synovial lining
