Knee Conditions Flashcards
Describe femoral hernias
Develop when an out-pouching of gastric viscera protrudes through the femoral canal
Protrusion becomes noticeable when it exits through the saphenous opening within the fascia lata = swelling inferior to the inguinal ligament
Describe the test for Trendelenburg’s Sign
Patient is asked to stand on one leg
If Tredenlenburg’s sign is positive, pelvis drops on unsupported side
Problem on stance leg, gluteus medius and minimus fail to lock the pelvis and cannot support the weight
Where are the safe areas for injections into the buttock
Need to avoid damaging sciatic nerve Dorsogluteal region (upper outer quadrant of the buttock) and Ventrogluteal region - to locate the ventrogluteal region, place the palm of one hand over the greater trochanter of the femur, point your thumb towards the inguinal region and your index finger toward the anterior superior iliac crest. Spread the index and middle fingers to make a V and inject between the PIPJ of your fingers into the gluteus medius muscle.
How does pathological locking of the knee come about
Unable to bend or extend the knee
True locking caused by a mechanical block where something gets stuck inside the joint, meniscus tear or loose body
Requires intervention - surgery
Valgus vs varus
Valgus - deviation of the distal limb away from the midline
Varus - deviation of the distal limb towards the midline
List common conditions of the knee
- Femoral shaft fractures
- Distal femoral fractures
- Proximal tibial fractures / tibial plateau fractires
- Patella fractures
- Patella dislocation
- Meniscal injuries
- Collateral ligament injury
- Cruciate ligament injury
- Pre-patellar bursitis
- Infrapatellar bursitis
- Compartment syndrome
Describe the cause and presentation of femoral shaft fractures
- Usually due to high velocity trauma - eg. Falls, road accidents
- Following the fracture, the proximal fragment is abducted due to pull of gluteus medius and minimus on the greater trochanter
- Leg also is flexed due to iliopsoas on the lesser trochanter
- Distal segment is adducted into a varus deformity due to the action of the adductor muscles and extended due to the pull of gastrocnemius on the posterior femur
Describe distal femoral fractures
- Usually due to high energy sporting injury causing significant displacement of the fracture fragment
- Popliteal artery may become involved - neurovascular examination
Describe proximal tibial fractures / tibial plateau fractures
- Fractures affecting the articulating surface of the tibia with the knee joint
- Fall onto an extended knee
- Often associated with meniscal tears and ACL injuries
- Can fracture one or both tibial condyles
- Knee swelling, pain on weight bearing, knee deformity
Describe patella fractures and presentation
- Due to direct impact injury or by indirect eccentric contraction
- Examination - palpable defect in the patella with swollen knee joint due to blood (haemarthrosis)
- Patient unable to perform a straight leg raise - lift leg off of bed by flexing at hip and extending at knee
Describe the types of patella fractures
- Stable fracture results in non-displacement
- Unstable fracture causes the broken ends of the bone to become separated and do not line up correctly
- Comminuted fracture shatters the bone into 3 or more pieces, can be stable or unstable
Describe presentation and cause of patella dislocation
- Most common direction is laterally
- Patella kept in position by contraction of the inferior fibres of vastus medialis
- Most common cause is trauma, often twisting injury or direct blow to the knee
- Eg. Changing direction quickly in sport
Describe cause and presentation of meniscal injuries
- Most common type of knee injury
- Occur as a result of a sudden twisting motion of the weight-bearing knee
- Present with intermittent pain, localised to the joint line
- Knee clicking, locking or sensation of giving way
Describe examination of meniscal injuries
- Examination shows joint line tenderness and restricted motion due to pain or swelling
- Mechanical block to motion or locking may occur
- Meniscal cyst may develop after tear during the healing response - causes discomfort to patient
- Acute haemathrosis may signify associated injuries of unhappy triad
Describe collateral ligament injury including presentation
- Common in sporting injuries from a direct blow to one side of the knee
- Medial and lateral collateral ligaments normally control the lateral movement of the knee joint and brace it against the unusual varus or valgus deformation
- Presents with immediate pain, swelling and stiffness
- MCL more commonly injured than LCL, but LCL tear has higher chance of causing knee instability
- MCL injuries commonly occur when the knee is slightly flexed
What is the unhappy triad
- Injury to the ACL, MCL and medial meniscus
- Results from a strong force applies to the lateral aspect of the knee
- Medial meniscus is firmly adherent to the MCL, so it becomes injured
How can ACL and PCL injuries be assessed
- ACL prevents anterior dislocation of tibia relative to femur and PCL prevents posterior dislocation
- ACL and PCL injuries can be detected using anterior and posterior drawer tests
- Lachmans test can be used to detect ACL injuries
Describe the cause of ACL injury
- ACL commonly torn due to quick deceleration, hyperextension or rotational injury that does not involve contact with another individual
- Often occurs following a sudden change in direction
- ACL can also be torn by large force to the back of the knee with the joint partly flexed
- Tibia may slide anteriorly under the femur
- Person typically reports popping sensation in the knee
Describe the cause of PCL injury
- Most common mechanism is dashboard injury - when the knee is flexed and a large force is applied to the upper tibia, displacing it posteriorly
- Also happens in sport when player falls on a flexed knee with their ankle plantarflexed
Describe pre-patellar bursitis including presentation
- Also known as housemaid’s knee
- Pre-patellar bursa located between the skin and the patella
- Presents with knee pain and swelling
- May be erythema overlying the inflamed bursa
- Difficulty walking due to pain, and will not be able to kneel on affected side
- Effusion - accumulation of excess synovial fluid within or around joint
- Usually due to repetitive trauma to bursa
Describe infrapatellar bursitis
- Also known as Clergyman’s knee
- Commonly affects the superficial infrapatellar bursa, which sits between the patella tendon (below the patella) and the skin
- Usually occurs due to repeated micro-trauma caused by activities involving kneeling
Describe the mechanism of compartment syndrome
- Compartments of limbs bound by bone and deep fascia
- Contain muscles with their nerve and blood supply as well as nerves and vessels running to distal structures
- Trauma to a fascial compartment may lead to haemorrhage and/or oedema, leading to rise in intracompartmental pressure
Describe the short term consequences of compartment syndrome
- Increase intracompartmental pressure leads to decreased perfusion of muscle causing ischaemia
- Ischaemic muscle releases mediators which further increase capillary permeability and increase pressure
- Neurovascular signs develop late
- Distal parenthesis precedes loss of motor function as thin cutaneous nerve fibres are affected more quickly
Describe the long term consequences of compartment syndrome
- Rhabdomyolysis (muscle necrosis) and AKI can occur
- Necrotic tissue may undergo fibrosis leading to Volkmann’s ischaemic contracture
- Permanent painful and disabling contracture of the affected muscle groups
Describe the presentation of compartment syndrome
- Severe pain in the limb, increasing and not relieved by analgesia
- Pain exacerbated by passive stretch of the muscles
- Treatment - surgical decompression
