MSK Flashcards
Achondroplasia
- impaired cartilage proliferation at the growth plate
- due to an autosomal dominant activating mutation in FGFR3, which inhibits growth
- most mutations are sporadic and related to increased paternal age; mutations are autosomal dominant with full penetrance; homozygosity is incompatible with life
- presents with short extremities but normal-sized head and chest since endochondral, but not intramembranous, bone formation is impaired
- mental function, life span, and fertility are all unaffected
- the most common cause of dwarfism
What is the difference between endochondral and intramembranous bone formation?
- endochrondral bone formation utilizes a cartilage skeleton and is the process through which long bones grow
- intramembranous does not involve a cartilage intermediate and is the process through which flat bones grow
Osteogenesis Imperfecta
- a congenitally defect resulting in structurally weak bone
- usually due to an autosomal dominant defect in COL1A1 or COL1A2, involved in type I collagen synthesis
- presents with multiple fractures, blue sclera because thinning of the scleral collagen reveals underlying choroidal veins, hearing loss because the ossicles fracture easily, and opalescent teeth that wear easily due to lack of dentin
- may be confused with child abuse, but in this case, bruising is absent
How can osteogenesis imperfecta be distinguished from child abuse upon examination?
osteogenesis imperfecta will present with fractures but bruises will be absent
Why does osteogenesis imperfecta present with blue sclera?
because thinning of the scleral collagen reveals the underlying choroidal veins
Osteopetrosis
- an inherited defect of bone resorption, which results in thick, heavy bone that fractures easily
- due to poor osteoclast function, most commonly because of a carbonic anhydrase II mutation, which impairs the ability of osteoclasts to form the acidic microenvironment necessary for resorption
- presents with bone fractures; anemia, thrombocytopenia, and leukopenia with extramedullar hematopoiesis because marrow is replaced by growing bone; vision and hearing impairment as bone growth impinges on cranial nerves; hydrocephalus as bone growth narrows the foramen magnum, and renal tubular acidosis
- x-rays show a “bone-in-bone” appearance
- treatment is a HSCT because osteoclasts are derived from monocytes
Which bone disease can be cured with a hematopoietic stem cell transplant? Why?
osteopetrosis because it is due to osteoclast malfunction and osteoclasts are derived from the monocyte lineage
Osteoclasts are derived form what cell lineage?
monocytes
Rickets
- vitamin D deficiency in children, with resulting hypophosphatemia and hypocalcemia, which leads to defective mineralization of osteoid
- deficiency is most often due to decreased sun exposure, poor diet, malabsorption, liver failure, or renal failure
- typically seen in children under the age of 1
- presents with pigeon-breast deformity (anterior protrusion of the sternum), frontal bossing, rachitic rosary, and bowing of the legs in ambulating children
- labs reveal hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and elevated alkaline phosphatase
- x-rays demonstrate “looser zones” also known as pseudofractures, epiphyseal widening, and metaphysical cupping/fraying
Osteoblasts produce what bone product?
osteoid
What is a Rachitic rosary?
- palpable osteoid deposition at the costochondral junction
- a feature of childhood Rickets
Osteomalacia
- vitamin D deficiency in adults, with resulting hypophosphatemia and hypocalcemia, which leads to defective mineralization of osteoid
- deficiency is most often due to decreased sun exposure, poor diet, malabsorption, liver failure, or renal failure
- osteoclast activity is fine so bone is resorbed and replaced by osteoid, increasing risk for fracture
- labs reveal hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and elevated alkaline phosphatase
- x-rays demonstrate “looser zones” also known as pseudofractures
What is alkaline phosphatase?
the enzyme expressed by osteoblasts that creates an alkaline microenvironment necessary for the precipiation and deposition of calcium in bone
Describe the synthesis of Vitamin D and it’s actions.
- normally vitamin D is derived form sun exposure and the diet- it is activated in the liver via 25-hydroxylation and then by 1-a-hydroxylation in the proximal tubule cells of the kidney
- it functions to increase serum calcium and phosphate by increasing absorption from the intestine, reabsorption in the kidney, and resorption of bone
Why does liver disease impair vitamin D activity?
because the liver is the site of 25-hydroxylation of vitamin D, the first step in activation of vitamin D
Why does renal disease impair vitamin D activity?
- 1-a-hydroyxlation, the final step of vitamin D activation, is performed by cells in the PCT of the kidney
- additionally, vitamin D acts on the kidney to increase calcium and phosphate reabsorption
- so damage impairs both the activation of and activity of vitamin D
Osteoporosis
- a reduction in trabecular bone mass defined by a DEXA more than 2.5 SD below normal or by a fragility fracture of the hip or vertebra
- risk is based on peak bone mass around age 30 and the rate of bone loss that follows (based on genetics, weight-bearing exercise, diet, and estrogen); most common in old age and post-menopause
- presents with bone pain and fractures in weight-bearing areas such as the vertebrae, hips, and distal radius
- labs are normal, which helps distinguish osteoporosis from osteomalacia
- treat with exercise, vitamin D, and calcium to limit further bone loss as well as bisphosphates to induce apoptosis of osteoclasts; can also use teriparatide, SERMS, denosumab, and rarely calcitonin
- estrogen therapy is currently not recommended and glucocorticoids are contraindicated
How can osteoporosis be distinguished from osteomalacia?
- via histology for one
- secondly, labs are normal in those with osteoporosis but abnormal in those with osteomalacia
How is bone density measured?
via a DEXA scan
At what point in our lives is peak bone mass achieved? What determines the level of this peak?
- peak is reached in early adulthood around age 30
- determined by genetics, such as vitamin D receptor variants; diet; and exercise
At what rate does bone loss after the age of 30 generally occur? What factors modify this rate?
- typically loss 1% of bone mass each year
- faster with lack of weight-bearing exercise, poor diet, or decreased estrogen
What effect does estrogen have on bone density?
it has a protective effect
Paget’s Disease of Bone
- a localized process that involves one or more bones, but not the entire skeleton, through an imbalance between osteoclast and osteoblast activity
- there are three distinct stages: first there is hyperactivity of osteoclasts and loss of bone; then there is a mixed phase in which both osteoclasts and osteoblasts are hyperactive as osteoblasts realize the bone loss and quickly lay down bad bone to try to make up for it; finally, the osteoclasts burn out and we have an osteoblastic phase
- the end result is thick, sclerotic bone that fractures easily
- presenting with bone pain (micro fractures), increasing hat size, hearing loss, lion-like facies, and an isolated elevated alkaline phosphatase
- complications include high-output cardiac failure, secondary to the formation of AV shunts in bone, and increased risk for osteosarcoma
- histology reveals a mosaic pattern of lamellar bone with frequent cement lines
- treat with calcitonin, which inhibits osteoclast activity, and bisphosphonates, which induce osteoclast apoptosis
What is the most common cause of isolated elevated alkaline phosphatase in patients over 40?
Paget disease of bone
Osteomyelitis
- an infection of the bone and marrow
- S. aureus is the most common cause in general, N. gonorrhoeae (young, sexually active), Salmonella (Sickle cell), Pseudomonas (diabetics or IV drug use), Pasteurella (dog/cat bite/scratch), and M. tuberculosis (Pott disease)
- more common in children for whom the metaphysics is seeded by a transient bacteremia; in adults it usually occurs from seeding of the epiphysis from an open-wound bacteremia
- presents with bone pain and signs of systemic infection
- x-ray reveals a lytic focus surrounded by a ring of reactive bone (i.e. sclerosis), called the sequestrum and involucrum, respectively
- diagnose using blood culture
What are the most common organisms that cause osteomyelitis?
- S. aureus is the most common cause in general
- N. gonorrhoeae is seen in sexually active young adults
- Salmonella is seen in those with Sickle cell
- Pseudomonas is seen in diabetics or IV drug abusers
- Pasteurella is associated with cat/dog bites/scratches
- M. tuberculosis spreads to the vertebrae and is known as Pott disease
What is the difference between childhood osteomyelitis and osteomyelitis affecting adults?
- in children, the metaphysis is generally seeded during a transient bacteremia
- in adults, the epiphysis is usually seeded by an open-wound bacteremia
What is a sequestrum and an involucrum?
- sequestrum is the central, lytic lesion of osteomyelitis
- the involucrum is a region of sclerotic or reactive bone surrounding it
Aseptic Necrosis of Bone
- aka avasulcar necrosis of bone
- a very painful infarction of bone and marrow due to ischemia
- causes include trauma or fracture, steroids, sickle cell, caisson disease (the Bend’s), Gaucher disease, and slipped capital femoral epiphysis
- Legg-Calve-Perthes disease is the idiopathic form
- most often involves the femoral head due to insufficiency of medial circumflex femoral artery
- major complications are osteoarthritis and fracture
Osteoma
- a benign tumor of bone
- most often arising on the surface of facial bones
- associated with Gardner syndrome (of FAP, fibromatosus in the retroperitoneum, and osteomas of the face)
What is Gardner syndrome?
- FAP
- fibromatosus in the retroperitoneum
- osteomas of the face
Osteoid Osteoma
- a benign tumor of osteoblasts, which produce osteoid, surrounded by a rim of reactive bone
- occurs mostly in males under the age of 25 in the cortex of long bones (most often the diaphysis)
- classically presents as bone pain that resolves with aspirin
- imaging will reveal a bony mass < 2 cm with a radiolucent core of osteoid
How does an osteoblastoma compare to an osteoma?
similar to osteoid osteoma but…
- greater than 2 cm in size
- arises most often in the vertebrae
- and presents as bone pain that does not respond to aspirin
Osteoblastoma
- a benign tumor of osteoblasts, which produce osteoid, surrounded by a rim of bone
- occurs predominantly in the vertebrae
- imaging typically reveals a bony mass > 2 cm with a radiolucent core of osteoid
- presents as bone pain that does not respond to aspirin
Osteochondroma
- a tumor of bone with an overlying cartilage cap
- arises from a lateral projection of the metaphysis, which then continues growing outward with bone being deposited beneath
- as a result, the bone is continuous with the normal marrow space
- the most common benign tumor of bone
- rarely, the overlying cartilage can transform into a chondrosarcoma
What is the most common benign tumor of bone?
osteochondroma
Osteosarcoma
- a malignant proliferation of osteoblasts
- greatest incidence is in teenagers, with another rise in prevalence in the elderly (bimodal); risk factors include familial retinoblastoma, Paget disease, radiation exposure, and Li Fraumeni syndrome
- arises in the metaphysis of long bones, most often the distal femur or proximal tibia around the region of the knee
- imaging reveals a destructive mass with a sunburst appearance that lifts the periosteum off the edge of the bone, creating Codman’s triangle
- presents with pathologic fractures or bone pain with swelling
- histology reveals pleomorphic cells that produce osteoid
What is Codman’s triangle?
the angle between the surface of a long bone and the periosteum at the site of an osteosarcoma where the periosteum has been pushed away from the length of the diaphysis
Giant Cell Tumor
- a bone tumor composed of multinucleate giant cells and stromal cells
- the only significant tumor that arises in the epiphysis of long bones
- most often in the distal demure or proximal tibia of young adults
- has a soap-bubble appearance on x-ray
- locally aggressive and may recur
Which primary bone tumor arises in the epiphysis of bones?
giant cell tumor
Ewing Sarcoma
- a malignant proliferation of poorly-differentiated cells derived from neuroectoderm
- arises in the diaphysis of long bones, typically in males less than 15 years of age
- characteristic (11;22) translocation causing fusion protein EWS-FLI 1
- has an “onion-skin” appearance on x-ray since tumor grows in the medullary cavity, pushing on the surface and triggering the periosteum to produce layers of new bone
- biopsy reveals small, round blue cells that resemble lymphocytes; as such it may be confused with lymphoma or osteomyelitis since it may present with fever
- often presents with metastasis but is responsive to chemotherapy
What is a t(11;22) mutation indicative of?
Ewing Sarcoma
What is a chondroma?
a benign tumor of cartilage that usually arises in the medulla of small bones of the hands and feet
What is a chondrosarcoma?
a malignant, cartilage-forming tumor that most often arises in the medulla of the pelvis or central skeleton
Where are chondromas and chondrosarcomas most likely to arise?
- chondroma: medulla of small bones in the hands and feet
- chondrosarcoma: medulla of the pelvis or central skeleton
Which cancers classically metastasize to the bone?
PB KTL
- prostate
- breast
- kidney
- thyroid
- lung
Which metastatic cancers to the bone are most likely to cause a blastic lesion?
- prostate is classically blastic
- breast is said to be mixed
What type of cartilage forms the articular surface of synovial joints?
hyaline
What type of collagen is found in the hyaline cartilage of synovial joints?
type II (car”two”lage)
What is the purpose of the synovium lining joint capsules?
secrete a fluid rich in hyaluronic acid to further lubricate the joint
Where does synovial fluid come from? What compound is highly concentrated within it for the purpose of additional lubrication?
the synovium produces a fluid rich in hyaluronic acid
Osteoarthritis
- the most common type of arthritis, it is a progressive degeneration of articular cartilage due to “wear and tear”
- risk factors include age, obesity, and trauma
- most often affects weight bearing joints and notably affects both DIPs and PIPs but not the MCPs
- presents with joint stiffness in the morning that worsens during the day; can often feel “joint mice” which are fragments of cartilage floating in the joint space
- histology shows disruption of cartilage, eburnation of the subchondral bone (“polishing”), and osteophyte formation, particularly in the DIPs and PIPs
- treat with acetaminophen, NSAIDs, and intra-articular glucocorticoids
What are Heberden nodes?
osteophytes of the DIPs
What are Bouchard nodes?
osteophytes of the PIPs
Rheumatoid Arthritis
- a chronic, systemic autoimmune disease that predominantly affects the joints
- HLA-DR4 haplotype is a risk factor
- joint destruction arises from synovitis causing granulation tissue formation, contributing to a pannus
- that pannus destroys the joint and causes joint fusion and deviation
- joint symptoms are worse in the morning/improve with activity, are symmetric, and spare the DIPs and first CMC
- non-joint signs include malaise, weight loss, myalgia, rheumatoid nodules, lung interstitial fibrosis, pleural effusion, and Baker cysts behind the knee
- rheumatoid factor (IgM against the Fc portion of IgG) is specific but anti-citrullinated peptide is more specific
- synovial fluid contains neutrophils and elevated protein; x-ray will show narrowing of joints, loss of cartilage, and osteopenia
- complications include anemia of chronic disease and secondary amyloidosis
- treat with NSAIDs glucocorticoids, disease-modifying agents (methotrexate, sulfasalazine, hydroxycholoroquine, and leflunomide), and biologics like TNFa inhibitors
What is a pannus?
- a form of synovitis in which the synovium becomes thickened by granulation tissue
- responsible for the joint destruction of rheumatoid arthritis
Which joints in the fingers are affected by rheumatoid arthritis?
the PIPs; DIPs are usually spared
What are the signs & symptoms of rheumatoid arthritis.
- symmetric involvement of the joints with sparing of the DIPs
- morning stiffness that improves with activity
- fever, malaise, weight loss, and myalgias
- rheumatoid nodules (central necrosis surrounded by epithelioid histiocytes on the skin or visceral organs)
- vasculitis
- baker cysts (swelling of bursa behind the knee)
- pleural effusions, LAD, and interstitial lung fibrosis
- joint space narrowing, loss of cartilage, and osteopenia on x-ray
- positive rheumatoid factor
- complications include anemia of chronic disease and secondary amyloidosis
What are rheumatoid nodules?
areas of central necrosis surrounded by epithelioid histiocytes on the skin or visceral organs
What are Baker cysts?
- a collection of popliteal fluid in the gastrocnemius-semimembranous bursa, commonly in communication with the synovial space
- related to chronic joint disease, especially rheumatoid arthritis
What is rheumatoid factor?
IgM against the Fc portion of IgG, which serves as a marker of tissue damage and disease activity in rheumatoid arthritis
What are seronegative spondyloarthropathies?
- a group of joint disorders characterized by a lack of rheumatoid factor, axial skeleton involvement, and an association with HLA-B27
- often associated with IBD
Ankylosing Spondyloarthritis
- a seronegative spondyloarthropathy (negative rheumatoid factor, axial skeleton involvement, and HLA-B27 association)
- arises in young adult males with low back pain as well as uveitis and aortitis leading to aortic regurgitation
- often see fusion of the vertebrae known as “bamboo spine”
Reactive Arthritis
- a seronegative spondyloarthropathy (negative rheumatoid factor, axial skeleton involvement, and HLA-B27 association)
- characterized by a triad of conjunctivitis, urethritis, and arthritis (“can’t see can’t pee, can’t climb a tree”)
- most often in young males weeks after a GI, Chlamydia trachomatis, or Campylobacter infection
Psoriatic Arthritis
- a seronegative spondyloarthropathy (negative rheumatoid factor, axial skeleton involvement, and HLA-B27 association)
- involves axial and peripheral joints with the DIPs of the hands and feet most commonly affected, leading to “sausage” fingers or toes
Infectious Arthritis
- that due to an infectious agent, usually bacterial
- causes include N. gonorrhoeae in young adults (most common) and S. aureus in older children and adults
- classically involves just a single joint, particularly the knee
- presents as a warm joint with limited range of motion, fever, increased white count, and elevated ESR
Describe uric acid biosynthesis. How is it eliminated from the body?
- AMP is converted to hypoxanthine and GMP to guanine
- these metabolites are then converted to xanthine and xanthine is converted to uric acid via xanthine oxidase
- uric acid is then moved into the blood and excreted by the kidney
Gout
- deposition of monosodium rate crystals in tissue, especially the joints due to hyperuricemia
- primary gout is the most common, but it can also arise in the setting of leukemia or myeloproliferative disorders in which there is increased cell turnover, Lesch-Nyhan syndrome (HGPRT reduces shunting of uric acid precursors through the purine salvage pathway), or renal insufficency (poor elimination)
- acute gout may be precipitated by consumption of alcohol or excessive amounts of meat and presents with painful arthritis of the great toe from crystal deposition and the resulting acute inflammatory reaction
- chronic gout leads to formation of tophi (white, chalky aggregates of uric acid crystals with fibrosis and giant cell reaction in the soft tissue joints) and renal failure due to rate crystal deposition in the tubules
- synovial fluid shows neutrophils and needle-shaped crystals with negative birefringence under polarized light; yellow under parallel light
- treat acute incidents with NSAIDs, glucocorticoids, and colchicine; use xanthine oxidase inhibitors like allopurinol or febuxostat as preventative treatment
What is the function of HGPRT?
it is an enzyme, named hypoxanthine-guanine phosphoribosyltransferase, that moves hypoxanthine (from AMP) and guanine (form GMP) into the purine salvage pathway
What is Lesch-Nyhan syndrome?
arises from a deficiency of HGPRT, an enzyme in the purine salvage pathway, which presents with gout, mental retardation, and self-mutilation
What two things are known to precipitate cases of acute gout? Why?
- alcohol competes with uric acid for excretion
- dietary meat adds lots of purine precursors that must be eliminated as uric acid
What is the name for the painful arthritis of the big toe that is seen in gout?
podagra
Chronic gout leads to what two symptoms/complications?
- formation of tophi
- deposition in renal tubules and renal failure
What are tophi? Where are they most likely?
- white, chalky aggregates of uric acid crystals with fibrosis and giant cell reaction in the soft tissue and joints, secondary to chronic gout
- most often on the external ear, olecranon bursa, or Achilles tendon
Pseudogout
- a disease that resembles the clinical features of gout but is instead due to the deposition of calcium pyrophosphate dihydrate
- these are rhomboid-shaped crystals with weakly positive birefringence under polarized right; blue under parallel light
- knee is most often affected
- x-ray often demonstrates cartilage calcification (chonedrocalcinosis)
- treat with NSAIDs, colchicine, and glucocorticoids for acute attacks; colchicine is also used for prophylaxis
What crystals are found in cases of pseudogout?
rhomboid-shaped, weakly positive birefringent calcium pyrophosphate dihydrate crystals
Dermatomyositis
- an inflammatory disorder of the skin and skeletal muscle
- etiology is unknown but there is an association with carcinoma, particularly gastric carcinoma
- presents with bilateral proximal muscle weakness as well as three types of rash: affecting the upper eyelids (heliotrope), malar rash, and red papule on the elbows, knuckles, and knees known as Gottron papules
- labs find positive ANA and elevated creatine kinase but most important is anti-Jo-1 antibody; also anti-SRP and anti-Mi-2 antibodies
- histology demonstrates perimysial inflammation (CD4) with perifascicular muscle fiber atrophy
- treat with corticosteroids followed by long-term immunosuppression like methotrexate
What are Gottron papule?
red papule on the knuckles, elbows, and knees in those with dermatomyositis
What is anti-Jo-1 antibody a feature of?
dermatomyositis
Malar rash and positive ANA can be seen in those with lupus as well as what MSK disorder?
dermatomyositis
Polymyositis
- an inflammatory disorder of skeletal muscle
- resembles dermatomyositis clinically in that there is proximal muscle weakness but there is no skin involvement
- most often involves the shoulders
- histology reveals endomysial inflammation (CD8) with necrotic muscle fibers
How can dermatomyositis and polymyositis be differentiated clinically and histologically?
- clinically: polymyositis doesn’t present with skin involvement like dermatomyositis does
- histologically: polymyositis is characterized by endomysial inflammation by CD8 cells with atrophy whereas dermatomyositis is characterized by perimysial inflammation by CD4 cells with atrophy
X-Linked Muscular Dystrophy
- a degenerative disorder characterized by muscle wasting and replacement of skeletal muscle by adipose
- due to an X-Linked recessive defect in the dystrophin gene, which encodes a protein important for anchoring the muscle cytoskeleton to the ECM
- mutations are often spontaneous and relatively common because the dystrophin gene is incredibly large; often a frameshift mutation that causes truncation of the protein product
- Duchenne presents with proximal muscle weakness at 1 year of age (begins in pelvic girdle and progresses superiorly), calf pseudo hypertrophy, and elevated creatinine kinase and aldolase
- Gower maneuver often seen, in which patients use upper extremities to help them stand, as is a waddling gait
- diagnosis is confirmed by Western blot
- those with Duchenne die due to cardiac (dilated cardiomyopathy) or respiratory failure secondary to replacement of the necessary muscles, including myocardium, with adipose
What do most with Duchenne’s muscular dystrophy die of?
cardiac or respiratory failure after the necessary muscles for either system are replaced by adipose
Myasthenia Gravis
- a disease characterized by autoantibodies against the post-synaptic ACh receptor at the neuromuscular junction and inhibit activation
- presents with muscle weakness, particularly affecting the eyes, that worsens with use and improves with rest; ptosis and diplopia are classic signs
- associated with thymus hyperplasia or thymoma, and in these cases a thymectomy improves the symptoms of myasthenia gravis
- use an edrophonium test for diagnosis and to determine if functional decline during treatment is due to too big or too small a dose of long-acting acetylcholinesterase inhibitors
- more common in women
Lipoblasts are characteristic of what pathology?
liposarcoma
What are the most common benign and malignant soft tissue tumors in adults? What is the most common malignant soft tumor in children?
- adult benign: lipoma
- adult malignant: liposarcoma
- child malignant: rhabdomyosarcoma
Cardiac rhabdomyoma is associated with what disease?
tuberous sclerosis
Rhabdomyosarcoma?
- a malignant tumor of skeletal muscle and the most common malignant soft tissue tumor in children
- characteristic cell is desman-positive rhabdomyoblasts
- commonly seen in the head or neck; and in the vagina of young girls (“grape-like” mass)
Lambert-Eaton syndrome
- a disease characterized by antibodies against pre-synaptic calcium channels of the NMJ, leading to impaired ACh release
- arises as a paraneoplasic syndrome in cases of small cell carcinoma of the lung
- presents with proximal muscle weakness that usually spares the eyes and that improves with use
- acetylcholinesterase agents do not improve symptoms
- resolves with resection of the cancer
How does Lambert-Eaton syndrome differ from myasthenia gravis?
- Lambert-Eaton is the result of antibodies against presynaptic calcium channels at the NMJ instead of post-synaptic ACh receptors
- Lambert-Eaton won’t improve with acetylcholinesterase inhibitors but will improve with use
- Lambert-Eaton usually spares the eyes
What is the anterior drawer sign?
an anterior gliding of the tibia indicative of ACL injury
What is the posterior drawer sign?
a posterior gliding of the tibia indicative of PCL injury
Where is the ACL located?
it extends from the lateral femoral condyl to the anterior tibia
How are the ACL and PCL named?
according to their relative position where they insert on the tibia
Where is the PCL located?
it extends form the medial femoral condyl to the posterior tibia
What sort of knee injury does abnormal passive abduction indicated?
it indicates an MCL tear
How would you identify a LCL tear of the knee during a physical exam?
it would show up as abnormal/excessive passive adduction of the knee
Describe the McMurray test and how it should be interpreted.
- a test used to identify a tear in either the medial or lateral meniscus
- the foot or tibia is rotated during flexion and extension of the knee while the patient is on his back
- pain or popping with external rotation indicates a medial meniscal tear
- pain or popping with internal rotation indicates a lateral meniscal tear
How would you test for a medial meniscal tear?
with external rotation during the McMurray test
What is the “unhappy triad” of knee injury?
- classically involves damage to the ACL, MCL and medial meniscus following a lateral force applied to a planted leg
- however, lateral meniscus tear is more common
- presents with knee pain and signs of instability
Prepatellar Bursitis
- inflammation of the knee’s largest sac of synovial fluid
- caused by repeated trauma or pressure from excessive kneeling
What muscles make up the rotator cuff?
SItS- superspinatus- infraspinatus- teres minor- subscapularis
What is the location, function, and innervation of the superspinatus muscle.
- it originates from the supraspinatous fossa of the scapula and inserts on the superior facet of the greater tubercle of the humerus (it is the superior muscle of the rotator cuff)
- it functions to abduct the arm until the deltoid takes over
- it is innervated by the suprascapular nerve off the upper trunk of the brachial plexus (C5,C6)
Which rotator cuff muscle is most often injured? Why?
the supraspinatous because it is commonly impinged upon while running through the subacromial space, leading to tendinopathy and tear
The empty/full can test is used to assess what muscle?
the supraspinatus of the rotator cuff
What is the location, function, and innervation of the infraspinatus muscle.
- it originates from the infraspinatus fossa of the scapula and inserts on the middle facet of the greater tubercle of the humerus (it is a posterior muscle of the rotator cuff)
- it laterally rotates the arm
- it is innervated by the suprascapular nerve off the upper trunk of the brachial plexus (C5,C6)
Pitching injuries often damage which portion of the rotator cuff?
the infraspinatus, responsible for laterally rotating the arm
What is the location, function, and innervation of the teres minor muscle.
- it originates from the lateral border of the inferior scapula and inserts on the inferior facet of the greater tubercle of the humerus (it is a posterior muscle of the rotator cuff)
- it adducts and laterally rotates the arm
- it is innervated by the axillary nerve
What is the location, function, and innervation of the subscapularis muscle.
- it originates from the subscapular fossa (anterior surface) and inserts on the lesser tubercle of the humerus (it is the anterior muscle of the rotator cuff)
- it adducts and medially rotates the arm
- it is innervated by the upper and lower sub scapular nerves
The rotator cuff primarily receives it’s innervations from where?
C5 and C6
Medial Epicondylitis
- aka golfer’s elbow
- it is an inflammation of the wrist flexor tendons that connect to the medial epicondyle
- due to repetitive flexion (forehand)
- presents with pain near the medial epicondyle
Lateral Epidondylitis
- aka tenis elbow
- it is an inflammation of the wrist extensor tendons that connect to the lateral epicondyle
- due to repetitive extension
- presents with pain near the lateral epicondyle
Name the wrist bones and their order.
So Long To Pinky, Here Comes The Thumb (towards pinky then towards thumb)
- Scaphoid, Lunate, Triquetrum, Pisiform (thumb to pinky)
- Hamate, Capitate, Trapezoid, Trapezium (pinky to thumb)
Which carpal bone is located in the anatomic snuff box?
the scaphoid
Which carpal bone is most commonly fractured?
the scaphoid
Scaphoid Fracture
- the most common carpal to be fractured
- usually from a fall onto an outstretched hand
- retrograde blood supply means that the bone is prone to avascular necrosis following a fracture
Which carpal bone may dislocate and cause an acute carpal tunnel syndrome?
the lunate
Which carpal bone, if damaged, can also injure the ulnar nerve?
the hook of the hamate
What runs beneath the hook of the hamate bone?
the ulnar nerve
Carpal Tunnel Syndrome
- entrapment of the median nerve in the carpal tunnel, which compresses the nerve
- presents with paresthesia, pain, and numbness in the distribution of the median nerve (i.e. palmar surface of lateral 3.5 fingers and hand plus dorsal surface of those same 3.5 fingers) as well thenar eminence atrophy without loss of sensation
- associated with repetitive use, pregnancy, rheumatoid arthritis, hypothyroidism, diabetes, and dialysis-related amyloidosis
Why does the thenar eminence atrophy without loss of sensation in those with carpal tunnel syndrome?
the motor nerve supplying the thenar eminence (recurrent branch of the median) arises after the median nerve passes through the carpal tunnel but the palmar cutaneous branch of the median nerve enters the hand external to the carpal tunnel to supply sensory innervation of the thenar eminence
Guyon Canal Syndrome
- compression of the ulnar nerve at the wrist or hand
- classically seen in cyclists due to pressure from the handlebars
- presents with paresthesia, pain, and numbness in the distribution of the median nerve
What would cause axillary nerve injury and how would it present?
- most likely damaged by a fracture of the surgical neck of the humerus or anterior dislocation of the humerus
- presents with flattened deltoid, loss of arm abduction past 15 degrees, and loss of sensation over the deltoid muscle and lateral arm
Which nerves and arteries would most likely be injured by the following humeral fractures:- surgical neck- midshaft- supracondylar- medial epicondyle
- surgical neck: axillary nerve and posterior circumflex humeral artery
- midshaft: radial nerve and deep brachial artery
- supracondylar: median nerve and brachial artery
- medial epicondyle: ulnar nerve and ulnar collateral artery
What would cause musculocutaneous nerve injury and how would it present?
- caused by compression of the upper trunk in the brachial plexus
- presents with loss of forearm flexion and supination, since is supplies motor innervation for the anterior arm, and a loss of sensation over the lateral forearm
What would cause radial nerve injury and how would it present?
- most likely caused by a midshaft fracture of the humerus or compression of the axilla (e.g. Saturday night palsy)
- presents with wrist drop, reduced grip strength, and loss of sensation over the posterior arm and forearm as well as over the dorsal hand
Why does ulnar nerve injury cause a reduction in grip strength?
because wrist extension is necessary for maximal action of flexors
What would cause median nerve injury and how would it present?
- proximal injury from supracondylar fracture of the humerus or distal injury from carpal tunnel or wrist laceration
- “Pope’s blessing” and from loss of wrist flexion, flexion of the lateral fingers, thumb opposition, and lumbricals of the 2nd and 3rd digits when trying to make a fist
- loss of sensation over the dorsal and palmar aspects of the later 3.5 fingers as well as thenar eminence with a proximal lesion
- positive Tinel sign (tingling to percussion)
