4: Anterior and Medial Thigh and Knee Flashcards
femoral shaft fractures
- in previously healthy and young adults, femoral shaft fractures normally due to high-velocity trauma
- in elderly, w osteoporotic bones or in pt w bone metastases/other bone lesions e.g. bone cysts, fractures can occur following low-velocity injuries
- musculature acts as deforming force following fracture
- proximal fragment often abducted due to pull of gluteus medius/minimus on greater trochanter and flexed due to action of iliopsoas on lesser trochanter
- distal segment adducted into varus deformity (action of adductors e.g. magnus and gracilis) and extended due to pull of gastrocnemius on posterior femur
how can a patient with a femoral shaft fracture present
- tight swollen thigh
- blood loss in closed femoral shaft fracture is 1000-1500ml and the patient may develop hypovolaemic shock
- blood loss in open fem fratures can be double amount
- complications due to involvement of neurovasculature is rare
how are femoral shaft fractures treated
surgical fixation
causes of distal femoral fractures and consequences
- younger pt = high-energy sporting injuries often w significant displacement of fracture fragments
- elder pt = in association w osteoporotic bone; usually a fall from standing
-
popliteal artery may become involved if there is significant displacement of fracture
- therefore careful assessment of neurovascular status of limb before and after reduction of fracture = essential
tibial plateau fractures
- tend to be high-energy injuries
- usual mechanism is axial (top to bottom) loading w varus or valgus angulation (abnormal medial or lateral flexion load) of knee
what do tibial plateau fractures affect
articulating surface of the tibia within the knee joint
- unicondylar or bicondylar
- fractures affecting lateral tibial condyle = most common
- articular cartilage is always damaged and despite careful approximation of fracture fragments, most pt = degree of post-traumatic OA in affected joint
what can tibial plateau fractures be associated with
meniscal tears and ACL injuries
what can cause patellar fractures
- direct impact injury e.g. knee against dashboard in car crash
- eccentric contraction of quads
- mostly occur in pt 20-50
consequences of patellar fracture
- patella = largest seasmoid bone and its most important blood supply is via inferior pole
- on examination = palpable defect in patella and haemarthrosis (blood in joint)
- if extensor mechanism is disrupted meaning fracture completely splits the patella distal to the insertion of quads, patient will be unable to perform a straight leg raise
how are patella fractures treated
- displaced patellar fractures require reduction and surgical fixation
- undisplaced fractures can be protected whilst healing using splinting and crutches (usually do not require surgery)
what can be mistaken for patellar fracture
- in some people , patella is bipartite meaning in 2 parts
- this develops because there is a failure of union of secondary ossification centre w main body of patella
- normal anatomical variant
patella dislocation and subluxation
refers to the patella being completely displaced out of normal alignment
- sublaxation = partial displacement
what is the most common direction for patella to dislocate and why
laterally
- due to ‘Q’ angle between line of pull of quadriceps tendon and patellar ligament
how is patella usually held in correct position
- by contraction of inferior, almost horixontal fibres of vastus medialis (vastus medialis obliquus or VMO)
- specific role of VMO is to stabilise patella within trochlear groove and control tracking of patella when knee is flexed and extended
common cause of patella dislocation and affected populations
trauma: often twisting injury in slight flexion or direct blow to knee
- age group most commonly affected are athletic teenagers and the usual mechanism is internal rotation of the femur on a planted foot whilst flexing the knee (e.g. in a sudden change of direction during sports)
what factors can predispose patellar dislocation
- Generalised ligamentous laxity
- Weakness of the quadriceps muscles, especially the VMO
- Shallow trochlear (patellofemoral) groove with a flat lateral lip
- Long patellar ligament
- Previous dislocations
what does treatment of patellar dislocation involve
- extending knee and manually reducing patella
- immobilisation used whilst healing
- followed by physio to strengthen VMO
meniscal injuries
- most common type of knee injury
- typically occur during sudden twisting motion of weight-bearing knee in high degree of flexion
how would a patient with a meniscal injury present
- intermittent pain localised to joint line + knee clicking, catching, locking or sensation of giving way
-
swelling occurs as delayed symptom due to reactive effusion or none as menisci largely avascular (except at periphery)
- therefore, acute haemarthrosis is therefore rare and if present, indicates a tear in the peripheral vascular aspect of the meniscus or an associated injury to the anterior cruciate ligament - chronic effusion (increased synovial fluid) can occur due to synovitis (inflammation of the synovial membrane)
what would you find on examination of a patient with meniscal injury
- joint line tenderness and restricted motion due to pain or swelling
- mechanical block to motion or locking can occur w displaces tear due to loose meniscal fragments becoming trapped between articular surfaces
how are meniscal injuries repaired
- acute traumatic meniscal tears are usually treated surgically by either meniscectomy or meniscal repair
- increasing evidence that meniscal tears that result from a chronic degenerative process within the knee have a similar prognosis with conservative management as with surgery
varus
medial angulation of the distal segment
valgus
lateral angulation of the distal segment
collateral ligament injury
- common sporting injury e.g. in football usually resulting from acute varus or valgus angulation of knee
- also work together w PCL to prevent excessive posterior motion of tibia on femur
is MCL or LCL injured more commonly
- MCL injured more commonly than LCL but torn LCL has higher chance of causing knee instability because medial tibial plateau forms deeper more stable socket for femoral condyle than lateral tibial plateau
- so intact LCL = more critical role in maintaining stability of knee
what will a patient suffering collateral ligament injury experience
- pain and swelling of knee
- as initial pain and stiffness subside, knee joint may feel unstable and pt may complain of it giving way
unhappy triad
injury to the anterior cruciate ligament, medial collateral ligament and medial meniscus
- results from a** strong force applied to the lateral aspect**of the knee
- medial meniscus is firmly adherent to the medial collateral ligament, which is why it is also injured
which is injured more commonly ACL or PCL
ACL as it is weaker
how is ACL usually injured
as result of quick deceleration, hyperextension or rotational injury e.g. following a sudden change of direction during sport
- can also be torn by the application of a large force to the back of the knee with the joint partly flexed
how will a patient with ACL injury present
popping sensation in their knee with immediate swelling
- When the swelling has subsided, the patient experiences instability of the knee as the tibia slides anteriorly under the femur
how can a PCL injury occur
- ‘dashboard injury’ where the knee is flexed and a large force is applied to upper tibia, displacing it posteriorly (seen in collisions when proximal leg collides w dashboard
- can also be torn during football when player falls on flexed knee w ankkle plantarflexed
- tibia hits the ground first and is displaced posteriorly, avulsing the PCL - severe hyperextension injury can also avulse the PCL from its insertion on the posterior aspect of the intercondylar area
how can ACL and PCL injuries be detected
using the anterior and posterior drawer tests
- Lachman’s test = ACL
dislocation of the knee joint
- uncommon injury and always results from high energy trauma
- in order to dislocate the knee, at least 3/4 ligaments must be ruptured (MCL, LCL, ACL, PCL)
why is an associated arterial injury common with dislocation of the knee joint
because popliteal artery is tethered proximally when it enters the popliteal fossa at the adductor hiatus and distally where it exits the popliteal fossa by passing under the tendinous arch of soleus muscle
why is the popliteal artery likely to be injured in dislocation of the knee joint
it is very immobile so if knee joint dislocates, high risk of injury
- may tear resulting in an obvious haematoma or can be crushed or suffer a traction injury (w endothelial damage leading to subsqeuent thrombotic occlusion)
- after reduction of knee joint, essential to fully assess the vascularity of the leg e.g. with Magnetic Resonance Angiography (MRA).
categorise swellings around the knee (3)
a) bony: e.g. Osgood-Schlatter’s disease
b) soft tissue
- localised e.g. an enlarged popliteal lymph node; popliteal artery aneurysm
- generalised e.g. lymphoedema
c) fluid
- inside joint = effusion
- outside joint = soft tissue haematoma
knee effusions
an accumulation of fluid inside the knee joint which is never normal
- acute (defined < 6hours after injury e.g. after cruciate ligament rupture)
- delayed (defined as > 6 hours after injury) usually due to reactive synovitis (Inflammation of the synovium, in response to injury, leads to the production of an increased volume of synovial fluid)
what can acute knee effusions be divided into
- Haemarthrosis (blood in the joint). Diagnostically, a haemarthrosis is an ACL rupture until proven otherwise.
- Lipo-haemarthrosis (blood and fat in the joint). A lipo-haemarthrosis is a fracture until proven otherwise as the fat has usually released from the bone marrow
describe what can be seen in a lipo-haemarthrosis on X-ray
- arrow shows a fat-fluid interface
- fat less dense than blood, absorbs fewer x-rays so appears darker than blood
bursitis of the knee
inflammation of a bursa
- most commonly inflamed = prepatellar, infrapatellar, pes anserinus (deep to common insertion of gracilis, ST and sartorius) and suprapatellar bursa
pre-patellar bursa
- pre-patellar bursa = superficial bursa w thin synovial lining, located between skin and patella
- does not communicate w joint space and usually contains minimal amount of fluid but inflammation –> marked increase of fluid within space
how does a patient with pre-patellar bursitis present
knee pain and swelling
- may be some erythema overlying inflamed bursa
- difficulty walking and not able to kneel on affected side
- usually history of repetitive trauma to bursa
- handmaids knee
infrapatellar bursa
- consists of two bursae, one of which sits superficially between patella tendon and the skin (most commonly affected)
- the second is referred to as the deep infrapatellar bursa and is sandwiched between patella tendon and tibia bone
infrapatellar bursitis
- occurs due to repeated microtrauma caused by activites involving kneeling
- clergymans
suprapatellar bursa
an extension of the synovial cavity of the knee joint so a knee effusion often presents w swelling in the suprapatellar pouch
- so rather than being a sign of localized irritation, “suprapatellar bursitis” is
more usually a sign of significant pathology in the knee joint
what are causes of a knee effusion
- Osteoarthritis
- Rheumatoid arthritis
- Infection (septic arthritis; see below)
- Gout and pseudogout
- Repetitive microtrauma to the joint (as a result of running on soft or uneven surfaces)
semimembranosus bursitis
- like suprapatellar bursitis, fluid in the semimembranosus bursa is an indirect consequence of swelling within the knee joint
- this bursa is located beneath the deep fascia of the popliteal fossa in interval between SM muscle and medial head of gastrocnemius
- attached to the posterior capsule of knee joint and may communicate with it by small opening
- if knee joint = inflamed + effusion, fluid can force its way through narrow communication into SM bursa
- aka popliteal cyst or Baker’s cyst
Osgood- Schlatter’s disease (OSD)
inflammation of the apophysis (site of insertion) of the patellar ligament into the tibial tuberosity
- most commonly occurs in teenagers who play sport (running and jumping) and causes localised pain and swelling. It is bilateral in 20-30% of cases
how does OSD present
intense knee pain during running, jumping, squatting, ascending and descending stairs and during kneeling
how is OSD treated
often resolved with** rest and ice**
- pain and swelling resolve at the age of skeletal maturity when the apophysis (which has a separate ossification centre) fuses
- but bony prominence usually remains permanently
what are the typical symptoms of knee OA
knee pain, stiffness and swelling
- pain can also follow a pattern for example:
- intermittent knee pain, chronic low level w more severe flare-ups
- pain precipitated by activities such as bending, kneeling, squatting or
climbing stairs
- pain and stiffness that is worse after prolonged inactivity or rest, such as
getting out of bed in the morning
signs of OA
- deformity of knee joint is common; e.g. patient may develop varus/valgus or fixed flexion deformity
- loss of articular cartilage –> friction –> crepitus
- effusion may develop and swelling further limits joint movement
- feeling of knee giving way or buckling likely due to muscle weakness –> instability of joint
- arthritis can be uni-, bi-, or tricompartmental (affecting one, two or all three of the medial femorotibial, lateral femorotibial and patellofemoral compartments)
what are risk factors of OA
age, female, previous trauma to joint, obesity, family history, other conditions e.g. RA, gout, septic arthritis
treatment plan for OA
- initially patients are taught strengthening exercises to strenghten vastus medialis muscle and therefore reduce instability
- analgesia and activity modification also used
- but ultimately, many patients will require surgery in form of total knee replacement
septic arthritis
the invasion of the joint space by micro-organisms, usually bacteria (but occasionally viruses, mycobacteria and fungi)
- it differs from reactive arthritis, which is a sterile inflammatory process that can result from an extra-articular infection e.g. gastroenteritis
- knee is the most common joint affected by septic arthritis (50% of cases), followed by the hip (20%), shoulder, ankle and wrists
pathogens causing septic arthritis of the knee
- most common: Staphylococcus aureus
- other pathogens: Staph. epidermidis, Neisseria gonorrhoeae (in sexually active individuals), Strep. viridans, Strep. pneumoniae and the Group B Streptococci
risk factors to consider for septic arthritis
- age
- DM
- RA
- immunosuppression
- IV drug abuse
what can increase risk of septic arthritis (outside of normal risk factors)
- prosthetic joints (joint replacements) are particularly at risk, either due to intraoperative contamination (60-80% of cases), or to haematogenous spread from a distant infective focus (e.g. during dental surgery)
- patient may become symptomatic months or even years after the initial operation
- delayed wound healing is a major risk factor for prosthetic joint infection; biofilm produced by Staph. epidermidis protects this pathogen from the host’s defences and from antibiotics
- Polymethacrylate cement used in the joint replacement also inhibits white blood cell and complement function, thereby increasing the risk of infection
what is the major consequence of bacterial invasion in septic arthritis
damage to articular cartilage, either due to organism’s pathologic properties (e.g. proteases secreted by Staph. aureus) or to the host’s immune response
- Neutrophils stimulate synthesis of cytokines and other inflammatory products, resulting in the hydrolysis of collagen and proteoglycans
typical triad of symptoms patient with septic arthritis present with
- Fever (40-60% of cases)
- Pain (75%)
- Reduced range of motion
- symptoms may evolve over a few days to a few weeks. The fever is usually low
grade with rigors present in only 20% of cases
what should you look for in septic arthritis
- joint should be examined for erythema (redness), swelling (90% have an obvious
effusion), warmth, tenderness, and limitation of active and passive range of motion - physical findings are usually minimal in infection of a prosthetic joint, and swelling is only slight
- most distinctive finding is a draining sinus (tract between the site of infection and surface of the overlying skin), which originates from the underlying infected joint
what should be done if septic arthritis is suspected
aspiration of the joint should be carried out immediately and the aspirate should be sent for urgent microscopy, culture and sensitivities
what are the main functions of the patella
- by enabling quadriceps muscle to directly cross anterior aspect of knee and acting as fulcrum, patella enhances leverage that Q. tendon can exert on femur = increase mechanical efficiency by 33-50%
- protection of anterior aspect of knee joint from physical trauma
- reduces frictional forces betweeen Q and femoral condules during extension of leg
describe the blood suply to the knee joint
through the genicular anastamoses around the knee which are supplied by the genicular branches of the femoral and popliteal arteries
- clinical relevance: if popliteal artery is gradually occluded by atheroma, genicular anastamoses can dilate to maintain blood supply to leg
what improves stability of knee joint
- tibial articular surface is deepened by menisci
- joint supported by joint capsule ligaments and surrounding musculature
- iliotibial tract plays a role in stabilising the lateral knee joint
- popliteus, the hamstrings and gastrocnemius all help stabilise the posterior aspect of the joint
what is a bursa
small sac lined by synovial membrane containing a thin layer of synovial fluid
- found in association w most of the major joints of the body
- can either be communicating or non-communicating
function of bursa
- provides a cushion between bones and tendon/muscles surrounding a joint
- helps to reduce friction between bones and soft tissues
- allows free movement
what are the six bursae found at the knee
- Suprapatellar bursa – This is an extension of the synovial cavity of the knee, located between the quadriceps femoris muscle and the femur.
- Prepatellar bursa – Found between the anterior surface of the patella and the skin.
- Superficial (or subcutaneous) infrapatellar bursa - Between the patellar ligament and the skin.
- Deep infrapatellar bursa - Between the tibia and the patellar ligament.
- Semimembranosus bursa – Posterior to the knee joint, between the semimembranosus muscle and the medial head of the gastrocnemius.
- Subsartorial (pes anserinus) bursa – Between the common insertion of the pes anserinus tendons (sartorius, gracilis, semitendinosus) and the medial tibial condyle
what are the four movements permitted by the knee joint
- extension: quadriceps femoris (rectus femoris, vastus medialis, lateralis and intermedius); insert –> tibial tuberosity via patellar ligament
- flexion: hamstrings (biceps femoris, semimembranosus, semitendinosus + gracilis, sartorius, plantaris and gastrocnemius)
- lateral/external rotation in flexed knee only: biceps femoris
- medial/interal rotation in flexed knee only: semimembranosus, semitendinosus, gracilis, sartorius and popliteus
explain the pop and lock mechanism of the knee
- when knee = fully extended, knee passively locks; 5° of medial (internal) rotation of the femoral condyles on the tibial plateau, cruciate ligaments tighten so lower limb = solid column adapted for weight-bearing
- in this locked position, thigh and leg muscles can relax briefly without making joint unstable
- to unlock knee, popliteus contracts which rotates the femur laterally by same amount on tibial plateau so flexion of the knee can occur
which muscles play an important role in stabilising the knee joint
quadriceps femoris; especially inferior fibres of vastus medialis aka vastus medialis obliquus (VMO or obliquus genus)
- these fibres contract to resist lateral displacementof patella out of trochlear groove
in which direction is the patella likely to be displaced and why
laterally: due to angle between ‘line of pull’ of the quadriceps muscle and the patellar ligament (known clinically as the Q angle)
which factors resist lateral displacement of the patella
- deep trochlear (patellofemoral) groove, which has a more prominent lateral femoral condyle anteriorly
- fibres of the VMO, which are inserted more distally into the patella and more horizontally than those of vastus laterali - contraction of these fibres resists the lateral displacement of the patella
describe the deep veins of the thigh
- once popliteal vein –> thigh via adductor hiatus = femoral vein
- this ascends in the adductor canal, accompanied by the femoral artery
-
profunda femoris vein follows course of its corresponding artery
- via perforating veins, it drains blood from thigh muscle into the distal section of femoral vein - common femoral vein leaves thigh by passing deep to inguinal ligament, medial to femoral artery = external iliac vein
describe the deep veins of the gluteal region
- drained by inferior and superior gluteal veins which follow course of relevant arteries
- empty into internal iliac vein
- obturator vein follows obturator artery and drains medial compartment of thigh
- enters pelvis through obturator foramen + obturator artery and nerve
what are the two major superficial veins of the lower limb
great (long) saphenous vein
small (short) saphenous vein
describe the path of the great (long) saphenous vein
- formed by dorsal venous arch of footand dorsal vein of great toe
- passes anteriorly to medial malleolus at ankle and ascends medial side of leg
- passes a hands breadth posterior to medial border of patella and ascends into medial aspect of thigh to pierce saphenous opening of fascia lata
- drains into femoral vein at saphenofemoral junction in femoral triangle
- receives many small tributaries as it ascends lower limb
describe the path of the small (short) saphenous vein
- formed by dorsal venous arch of footand dorsal vein of little toe
- passes posterior to lateral malleolus at ankle and along lateral border of Achilles (calcaneal) tendon
- ascends posterior leg and passes between two heads of gastrocnemius
- drains into popliteal vein at saphenopopliteal junction in popliteal fossa
what are the superificial lymphatic vessels divided into
medial vessels
- closely follow the course of the great saphenous vein
- drain into the inferior group of superficial inguinal lymph nodes in the femoral triangle
lateral vessels
- follow the course of the small saphenous vein and either drain into popliteal lymph nodes in the popliteal fossa
- or cross to join the medial group just below the knee and drain into the superficial inguinal lymph nodes
- efferent lymphatic vessels from the popliteal nodes follow the femoral vein and drain into the deep inguinal nodes
deep lymphatic vessels
- far fewer in number than their superficial counterparts and accompany the deep arteries of the leg (i.e. the lower limb below the knee)
- found in three main groups: anterior tibial, posterior tibial and peroneal following the corresponding artery respectively, and entering the popliteal lymph nodes
