Flashcards in 4.1 The Knee disorders Deck (31):
How do femoral shaft fractures occour?
High velocity trauma
Elderly with osteoporotic bone or bone metastasis or other bone lesions e.g bony cysts, fracture can occur from low velocity injury.
In children consider child abuse
What happens to the proximal portion of a femoral shaft fracture?
It’s abducted due the pull of the gluteus mediums and minimums on the greater trochanter
It’s also flexed due to the action of iliopsoas on the lesser trochanter
What happens to the distal segment on a femoral shaft fracture?
It will be adducted into a varus deformity due to the action of adductor muscles
- adductor Magnus
And extended due to the pull of gastrocnemius on the posterior femur.
What will the patient feel in a femoral shaft fracture?
Tense swollen thigh
May have hypovolaemic shock
How do distal femoral fractures occur?
Younger = high energy sporting injury
Elderly = osteoporotic bone, fall from standing
What artery may be involved in a distal femoral fracture?
Popliteal artery may be involved if there’s significant displacement of the fracture
How can you tell from an x ray that you’re looking at a child?
What will you see upon examination of a patella injury?
Palpable defect in patella and joint will be swollen due to blood (haemathrosis)
The patient will be unable to perform a straight leg raise
What is the most common direction for patella dislocation and how does it occour?
Mostly laterally dislocations
Due to TRAUMA
Occurs in athletes who may suddenly change direction running during sports
How is the patella kept in place?
The vastus medallus obliquus (VMO) which is an inferior horizontal fibre of the vastus medialis
Stabilised the patella within the patella groove
How can you be predisposed to a patellar dislocation?
- weakness of quadriceps muscles, especially VMO
- shallow patella groove in femur
- patellofemoral joint hypermobility or maltracking
Why do meniscal injuries occur and what will you observe upon examination?
Occur due to a sudden twisting motion of the weight bearing knee
Patient usually has joint line tenderness and restricted motion due to pain or swelling
Swelling is usually delayed/absent as menisci are avascular expect periphery. So, if swollen, due to tear in periphery or an associated injury to the anterior crucial ligament.
What is a chronic effusion and how is it linked to synovitis?
Chronic effusion = increased synovial fluid
Synovitis = inflammation of synovial membranes
Chronic effusion can occur due to synovitis
What is the difference between varus and valgus deformation?
Varus = medial angulation of distal segment
Valgus = lateral angulation of distal segment
Remember vaLgus = Lateral
What ligaments control varus of valgus deformation in the knee joint?
Medial and lateral collateral ligaments keep knee in place
Posterior cruciate ligament chimes in to prevent excessive posterior motion of the tibia on the femur
What ligament is more to injury and which is worse if torn, the medial collateral ligament or the lateral collateral ligament?
Medial collateral ligament = more prone to injury
Lateral collateral ligament = worse if injured. This is because the medial tibial plateau forms a deeper and more stable socket with the femoral condyle than the lateral plateau.
What’s the unhappy triad?
- anterior cruciate ligament
- medial collateral ligament
- medial meniscus
Results from a strong force applied to the lateral aspect of the knee.
Where to the anterior and posterior cruciate ligament extend from?
Extend from the intercondylar eminence of the tibia to the intercondylar notch of the distal femur
ACL attaches to posterior aspect of femoral notch and the anterior intercondylar region of the tibia.
PCL goes from medial edge of lateral femoral condyle and the roof of the intercondylar notch. It stretches posterolaterally towards to posterior surface of the tibia.
What do the ACL and PCL do?
ACL resists anterior translation and medial rotation of the tibia in relation to the femur
PCL prevents posterior dislocation of the tibia on the femur
How is the ACL usually torn and what does the patient feel?
As a result of quick deceleration, hyperextension or rotational injury
The tibia can slide anteriorly under the femur
Usually feel a popping sensation in the knee.
How is the PCL damaged?
Dashboard injury = flexion of the knee and a force placed on the upper tibia, displacing it posteriorly
Also during football when a player falls on a flexed knee when their ankle plantar flexed
What’s prepatella bursitis and how will patients present?
Inflammation of the prepatella bursa. A superficial bursa between the skin and patella.
Inflammation causes increase in fluid.
Patient has pain and swelling, cant kneel on affected knee and cant walk due to pain.
Usually a history of repetitive trauma to the bursa e.g kneeling on the ground to scrub = housemaids knee.
What is infrapatella bursitis and how does it occur?
Two bursa - one below the knee cap and one deep between the patella tendon and tibial bone (shin).
Usually superficial one is inflammed
Occurs due to repeated micro trauma e.g repeated kneeling. Clergymans knee = common nickname and reflects upright position of kneeling.
What’s suprapatella bursitis
Swelling within the suprapatellar pouch presents with a knee effusion.
It’s usually a sign of pathology in the knee. Causes can be osteoarthritis or rheumatoid arthritis, gout, infection, repetitive microtrauma, ect.
What’s osgood schlatters disease and what do patients complain of?
Inflammation of the patellar ligament at its insertion into the tibial tuberosity. Commonly occours in teenagers who play sport.
Complain of intense knee pain during running, jumping, squatting, ascending and descending stairs and during kneeling.
Resolves with rest and ice.
What are the symptoms of osteoarthritis in the knee?
Pain comes and goes at varying levels of intensity
Pain precipitated by activities e.g bending, kneeling, squatting or climbing stairs
Pain is worse after prolonged inactivity or rest e.g getting out of bed in the morning.
Knees may buckle when going downstairs due to weakness of quads causing instability
Loss of articular cartilage = bone rubs on bone = firiction can be felt as crepitus. An effusion may develop.
What are the risk factors with OA and what will you see on an X-ray?
- gender (female)
- other conditions effecting the joint
- previous trauma to the joint
- family history
- narrow joint space
What is septic arthritis of the knee joint and what is the most common cause?
Inflammation caused by the invasion of micro organisms in the joint space
Isn’t sterile unlike reactive arthritis
- staphlylococcus aureus
- staph pneumonia
- neiserria gonorrhoea
- group B streptococci
- strep viridans
What are the risk factors for septic arthritis?
Age, diabetes mellitus, rheumatoid arthritis, immunosuppressive and IV drug use
Prosthetic joint replacement also. May become symptomatic months or years after initial operation maybe due to delayed wound healing. Biofilm produced by staph epidermis protects bacteria from destruction by antibodies or bodies immune response.
What’s the major consequence of septic arthritis?
Damage to articular cartilage due to organisms pathological properties or hosts immune response (neutrophils stimulate cytokines which hydrolyse collagen and proteoglycans).