MSK Flashcards500-End
How many degrees of freedom does the knee have?
6: 3 translational and 3 rotational. Obviously the flexion and extension is the “normal” degree of freedom, but the others are also significant particularly once ligaments are injured.
What is varus/valgus rotation of the knee?
Valgus means pointing the tibia/fibia outward (duck feet), except when this happens at the knee joint instead of the hip joint (varus is the opposite)
What is the typical history for an ACL tear?
A pop or crack, pain and immediate swelling of the knee followed by instability
What other common injuries associate with an ACL tear?
Meniscal damage, chondral injuries, and MCL/PCL/LCL
Is the MRI useful for diagnosing possible ACL damage?
Yes, it can visualize the ligaments and the meniscus
Does the ACL always heal without surgery? What about the MCL?
No, probably due to the synovial environment; the MCL does heal since it is outside the joint
Can the ACL be sewn together? What is the typical surgery process?
There is low success rate with this; it is reconstructed through autograft or allograft
What are the two most common complications of ACL surgical repair? What is their collective incidence?
Stiffness and the graft not healing correctly; 2%
What are two options for treating a diagnosed ACL injury?
Rehabilitation with modified patient activity and surgery
How long is rehab for an ACL surgery?
4-6 months
What bone does the talus attach to inferiorly within the ankle?
Calcaneus
Are these two little bumps on the first metatarsal normal? What are they?
Yes; sesamoid bones (bones inside tendons)
What are the sensory innervations for these three areas of the anterior (dorsal) foot?
Top to bottom, sural, saphenous, and superficial peroneal
What nerve provides sensory innervation to the part of the foot stimulated in the Babinski test?
Lateral plantar branch of the the medial plantar nerve (from the tibial nerve)
Between toe fractures or metatarsal injuries, which are more likely to require surgery?
Metatarsals (they are often crush injuries of multiple bones)
Are the toe bones hollow? What are the implications on surgical reduction?
Yes; a pin can be put in the medullary space
What kind of fracture is this? Why might it not heal?
Jones fracture; poor blood supply to this region
What is a Lisfranc fracture?
A tarsometatarsal joint dislocation
What is the treatment for this kind of fracture?
Open reduction internal fixation (surgery)
What classification system is used for talus fractures? For calcaneus fractures?
Talus__Hawkins; Calcaneus__Sanders
What bone is fractured in this CT?
The head of the talus, also causing a dislocation of the subtalar joint
Tearing of what ligament has allowed the tibia to shift medially in this fibular fracture?
Deltoid (or talocrural) ligament
What condition along with its associated neuropathy can cause progressive deterioration of the ankle joint, including fractures?
Diabetes
What are the two most common crystals found in synovial fluid that cause synovitis?
Monosodium urate (gout) and calcium pyrophosphate/dihydrate (pseudogout)
Is gout predisposition inheritable? Does it occur more in men or women?
Yes; men
What serum abnormality precedes acute gout?
Asymptomatic hyperuricemia
In familial gout, what enzyme deficiency is likely?
HGPRT or G6PD
What social history is relevant to a diagnosis of gout?
Alcohol consumption, which can cause overproduction and underexcretion of uric acid
Is it more common for hyperuricemia to be caused by overproduction or underexcretion of uric acid?
Underexcretion (90%)
What drugs can cause underexcretion of uric acid?
Diuretics, low dose aspirin, heparin, cyclosporine
Which endocrine disorder can lead to hyperuricemia and gout?
Hypothyroidism
Are first attacks of gouts usually monarticular or polyarticular? Which joint(s) are affected?
Monarticular; 1st MTP (podagra, big toe), dorsum of foot, ankle, knee
What time of day does gout usually start?
Night
What happens without treatment of acute gout or pseudogout?
It resolves by itself over ~1 week
What variant of gout is seen here?
Podagra: 1st MTP
What organ system insufficiency exacerbated by obesity contributes the most to development of gout?
Renal insufficiency
Is synovial fluid from gout inflammatory? Are there increased WBCs?
Yes; yes, >5k up to 100k
What is this slide of synovial fluid diagnostic of? Does it matter that the spikes are inside a cell?
Gout; yes, the uric acid crystals must be inside a neutrophil, because there are normally some free floating crystals in synovial fluid
With what drugs is acute gout treated?
NSAIDs, colchicine, and intra-articular or systemic steroids
Is uric acid lowering therapy indicated for acute monarticular gout? Why or why not?
No, it is contraindicated__you only try it after recurrent attacks despite colchicine prophylaxis; trying to lower uric acid with drugs causes a large flux across plasma membranes, which can cause crystal formation in other joints
What prophylaxis can be used to treat intercritical gout?
Colchicine
What dietary modification may be suggested for somebody with intercritical gout?
Foods like red meat, seafood, or beans that are high in uric acid should be avoided, but most particularly alcohol
These small skin features are associated with what synovial disease?
Gout (these are small subcutaneous crystals of uric acid)
This is an extreme example of what joint disease? The lesion has crystalline substance leaking from it.
Gout
What is the difference in function between a uricosuric agent and xanthine oxidase inhibitor?
Uricosuric agents increase excretion of uric acid, while xanthine oxidase inhibitors decrease production of uric acid
Would a gout patient who is an underexcreter receive a xanthine oxidase inhibitor or a uricosuric agent?
Uricosuric agent
Of the following, label which are uricosurics and which are xanthine oxidase inhibitors (XOI):
__ Allopurinol
__ Probenecid
__ Oxypurinol
__ Febuxostat
__ Allopurinol: XOI
__ Probenecid: uricosuric
__ Oxypurinol: XOI
__ Febuxostat: XOI
Does pseudogout usually present as a monarticular or polyarticular disease? Is the first MTP a typical place for it?
Monarticular; no
What are the top four joints that pseudogout will present in?
Knee, ankle, hip, shoulder blade
Is synovial fluid in pseudogout inflammatory? Is it typically higher or lower in WBCs than gout?
Yes; lower, around 20-40k
What crystalline substance is found intracellularly in synovial fluid for a pseudogout patient?
Calcium pyrophosphate
What is the clue on this X-ray that the patient might have pseudogout? Is this clue specific for pseudogout in an older patient?
The thin line of calcification of cartilage along the joint margin (chondrocalcinosis); no, many older patients have it
What form of arthritis is a risk factor for pseudogout?
Osteoarthritis
What endocrine disorders associate with pseudogout?
Hyperparathyroidism and hypothyroidism
How is pseudogout treated?
NSAIDs, colchicine, and intra-articular steroids
This X-ray is from an elderly patient with localized tendonitis, with acute shoulder pain. What happened? What differentiates it from Milwaukee shoulder?
Calcific tendinitis: note the calcium hydroxyapatite deposition above the head of the humerus; it is in the tendon within the bursa, not the joint capsule
What is the typical gender and age for Milwaukee shoulder? What arm is usually affected?
Elderly women; dominant arm
How is Milwaukee shoulder treated?
NSAIDs, colchicine, aspiration, intra-articular steroids
What is the name for crystal synovitis involving calcium hydroxyapatite deposition in the glenohumeral joint? What muscles can be torn in association with it?
Milwaukee shoulder; rotator cuff
What are the three layers of connective tissue within a muscle, from outermost to innermost? Which one surrounds individual fibers?
Epimysium, perimysium, endomysium; endomysium surrounds fibers
What is this circular structure within a ped patient’s muscle? Is it normal?
A muscle spindle (not a vessel! it contains muscle fibers and growing nerves); yes
How many types of myofibers are there? Which one is “fast twitch”? Which one has more fat?
Two types; fast twitch is type 2 (white); more fat is type 1 (red)
What are the two different kinds of fibers stained in this section of muscle?
Type 1 and type 2, which differentiates slow and fast twitch
Which type of muscle fiber has more mitochondria?
Type 1 (slow twitch)
What is one “motor unit”?
An anterior horn motor neuron, its axon, and the muscle fibers it innervates
What neurotransmitter receptor is highly concentrated in these invaginations of the cell membrane? What enzyme is also there to prevent overstimulation?
ACh receptor; acetylcholinesterase
What construct is used by the muscle to produce a coordinated Ca++ efflux from the sarcoplasmic reticulum in response to a propagated action potential?
T-tubules
Are neurogenic or myopathic causes of muscle disorders more common?
Neurogenic
What has happened to some of the myofibers in this muscle?
They have atrophied, becoming angular and shrunken
Why might a group of myofibers fail to show a typical even distribution between Type 1 and Type 2 fibers?
If one type of motor neuron dies and its cells become detached and atrophy, they send signals to regain collateral innervation from the other type
Will an ALS patient show fiber type grouping on histological study of atrophic muscles?
Yes
Do you get neurogenic atrophy with a stroke? Why does atrophy occur on the side of the body contralateral side to the stroke?
No, because it is the UMN that is affected and not the LMN; atrophy occurs because of disuse
Does disuse atrophy preferentially affect type 1 or type 2 myofibers?
Usually, type 2
Do myopathies tend to be proximal or distal? What about neuropathies?
Myopathies __ proximal (left);
Neuropathies __ distal (right, stocking/glove)
What is the inheritance pattern of Duchenne’s muscular dystrophy?
X-linked recessive
When does Duchenne’s present?
5 years old
Is a diagnosis of muscular dystrophy supported by a positive Gowen’s sign? What is Gowen’s sign?
Yes; walking the body into an upright position with the arms and hands
What X-linked recessive condition is associated with the following presentation in a 5 year old?
Duchenne’s muscular dystrophy
What gene is affected by Duchenne’s muscular dystrophy? Where is the gene within the genome? Is it a large or small gene?
Dystrophin; small arm of X chromosome; very large
This mother was stained for the dystrophin protein and the following pattern results. What is her likelihood for each of her sons in developing Duchenne’s?
50%, since the mom is clearly a carrier (mosaic pattern), and the disease is X-linked recessive
Collectively, muscular dystrophies are diseases of what molecular complex? What does it connect?
The dystrophin-glycoprotein complex; the basal lamina, sarcolemma, and F-actin
What is the difference between Becker’s and Duchenne’s muscular dystrophies?
The same gene (dystrophin) is involved, but the mutation causes a less severe phenotype
What is the most common dystrophy that presents in adults?
Myotonic dystrophy
What is the genetic basis for myotonic dystrophy? What neurodegenerative disease is caused by a similar kind of mutation?
A mutation in the myotonin kinase gene, specifically an expansion of a trinucleotide repeat; Huntington’s
Does the number of repeats in myotonin kinase correlate proportionally or inversely with the age of onset of myotonic dystrophy?
Inversely
What type of myofiber is preferentially affected by a congenital myopathy? How does the patient present?
Type 1 myofiber; “floppy baby”
Malignant hyperthermia results from a mutation in what gene? What tissue type causes the release of heat in this disease?
Ryanodine receptor; muscle fibers continuously burning energy and contracting
What is a “ragged red” segment of muscle?
An area where abnormal mitochondria have undergone extreme proliferation due to some abnormality in the mtDNA, and may be visible with red mitochondrial stains or with strange crystal inclusions under EM
What is an intrinsic inflammation of many skeletal muscles called?
Polymyositis
What is happening to this muscle fiber? If this is happening throughout normal muscles in the body, what condition is this?
It is being invaded by immune cells, and will eventually become necrotic; polymyositis
What is the clinical opposite of myasthenia gravis, whereby the strength of an NMJ increases with repetitive stimulation? What cancer does that disease associate with?
Eaton-Lambert, a disease of the presynaptic axon terminal; small cell lung carcinoma
What is the most often cause of cancer affecting the bone?
Metastatic bone disease
What are the two most common sources of cancer cells that metastasize to bone?
Prostate and breast
What are the two most common primary malignant bone tumors?
Osteosarcoma and chondrosarcoma
Are osteoid osteomas and osteoblastomas benign or malignant?
Benign
Are osteosarcomas benign or malignant?
Malignant
Why are osteoid osteomas painful? Why is this relieved by NSAIDs like ASA?
Prostaglandin E2 is secreted by proliferating osteoblasts; ASA inhibits prostaglandin production
What part of the bone are osteoid osteomas found in?
Diaphysis, cortical bone
What differentiates osteoid osteomas from osteoblastomas on histological examination?
They are similar in that the structure is disrupted within cortical bone, but osteoblastomas do not have a reactive periphery
Are osteoblastomas generally larger or smaller than osteoid osteomas?
Larger
Do osteosarcomas tend to present in teens or older patients?
Teens
What is this fluffy stuff surrounding the figure in this malignancy?
Osteoid depositing into the soft tissue by a osteosarcoma
Do osteosarcomas arise in the epiphysis, metaphysis, or diaphysis of a long bone?
Metaphysis
What kind of a bone tumor is this? It is the most common primary malignancy of bone.
Osteosarcoma
How does osteosarcoma spread? Where is the typical metastatic destination? How is it treated?
Hematogenously; lungs; pre-op chemotherapy and surgery