Musculoskeletal, Skin, and Connective Tissue: Anatomy and Physiology

Question 1

Anterior Drawer Sign (Test)

Answer 1

Bending knee at 90° angle, increased anterior gliding

of tibia due to ACL injury. Lachman test is similar, but at 30° angle.

Question 2

Posterior Drawer Sign (Test)

Answer 2

Bending knee at 90° angle, decreased posterior gliding of tibia due to PCL injury.

Question 3

Abnormal Passive Abduction

Answer 3

Knee either extended or at ∼ 30° angle, lateral
(valgus) force Ž–> medial space widening of
tibia –>Ž MCL injury.

Question 4

Abnormal Passive Adduction

Answer 4

Knee either extended or at ~ 30° angle, medial
(varus) force –>Ž lateral space widening of tibia –>
Ž LCL injury.

Question 5

McMurray test

Answer 5

During flexion and extension of knee with
rotation of tibia/foot:
ƒƒ Pain, “popping” on external rotation –> medial meniscal tear
ƒƒ Pain, “popping” on internal rotation –> lateral meniscal tear

Question 6

ACL

Answer 6

Anterior Cruciate Ligament

Extends from lateral femoral condyle to anterior tibia

Question 7

PCL

Answer 7

Posterior Cruciate Ligament

Extends from medial femoral condyle to posterior tibia

Question 8

“Unhappy Triad”

Answer 8

Common injury in contact sports due to lateral force applied to a planted leg. Classically, consists of damage to the ACL, MCL, and medial meniscus (attached to MCL); however, lateral meniscus injury is more common. Presents with acute knee pain and signs of joint injury/instability.

Question 9

Prepatellar bursitis

Answer 9

Inflammation of knee’s largest sac of synovial fluid (ventral). Can be caused by repeated trauma or
pressure from excessive kneeling.

Question 10

Baker cyst

Answer 10

Popliteal fluid collection in gastrocnemius-semimembranous bursa commonly communicating
with synovial space and related to chronic joint disease.

Question 11

Rotator cuff muscles

Answer 11

SItS
Supraspinatus (suprascapular nerve)
Infraspinatus (suprascapular nerve)
teres minor (axillary nerve)
Subscapularis (upper and lower subscapular nerves)

Innervated primarily by C5 and C6

Question 12

Supraspinatus

Answer 12

Rotator cuff muscle
(suprascapular nerve)
Abducts arm initially (before the action
of the deltoid); most common rotator cuff
injury (trauma or degeneration and
impingement Ž--> tendinopathy or tear),
assessed by “empty/full can” test.

Question 13

Infraspinatus

Answer 13

Rotator cuff muscle
(suprascapular nerve)
Laterally rotates arm; pitching injury

Question 14

teres minor

Answer 14

Rotator cuff muscle
(axillary nerve)
Adducts and laterally rotates arm

Question 15

Subscapularis

Answer 15

Rotator cuff muscle
(upper and lower subscapular nerves)
Medially rotates and adducts arm

Question 16

Medial Epicondylitis

Answer 16

Overuse Injury of Elbow
“Golfer’s Elbow”
Repetitive flexion (forehand shots) or idiopathic –>Ž pain near medial epicondyle.

Question 17

Lateral Epicondylitis

Answer 17

Overuse Injury of Elbow
“Tennis Elbow”
Repetitive extension (backhand shots) or idiopathic –> pain near lateral epicondyle

Question 18

Wrist Bones

Answer 18

Scaphoid, Lunate, Triquetrum, Pisiform, Hammate, Capitate, Trapezoid, Trapezium (So Long To Pinky, Here Comes The Thumb)

Question 19

Scaphoid

Answer 19

(palpated in anatomic snuff box)
Most commonly fractured carpal bone (typically from a fall on an outstretched hand) and is prone to avascular necrosis owing to retrograde blood supply

Question 20

Lunate

Answer 20

Dislocation may cause acute carpal tunnel syndrome

Question 21

Hook of Hamate

Answer 21

A fall on an outstretched hand that damages
the hook of the hamate can cause ulnar nerve
injury.

Question 22

Carpal Tunnel Syndrome

Answer 22

Entrapment of median nerve in carpal tunnel; nerve compression Ž paresthesia, pain, and
numbness in distribution of median nerve (thenar eminence atrophies but sensation spared,
because palmar cutaneous branch enters the hand external to carpal tunnel). Associated with
pregnancy, rheumatoid arthritis, hypothyroidism, diabetes, dialysis-related amyloidosis; may be
associated with repetitive use.

Question 23

Guyon Canal Syndrome

Answer 23

Compression of ulnar nerve at wrist or hand. Classically seen in cyclists due to pressure from
handlebars.

Question 24

Axillary Nerve (C5-C6)

Answer 24

Upper extremity nerve
Causes of injury: Fractured surgical neck of humerus; anterior dislocation of humerus
Presentation: Flattened deltoid; loss of arm abduction at shoulder (>15 degrees); loss of sensation over deltoid muscle and lateral arm

Question 25

Musculocutaneous Nerve (C5-C7)

Answer 25

Upper Extremity Nerve Causes of Injury: upper trunk compression Presentation: loss of forearm flexion and supination; loss of sensation over lateral forearm

Question 26

Radial Nerve (C5-T1)

Answer 26

Upper Extremity Nerve Causes of injury: Midshaft fracture of humerus; compression of axilla, eg, due to crutches or sleeping with arm over chair (“Saturday night palsy”) Presentation: Wrist drop: loss of elbow, wrist, and finger extension; decreased grip strength (wrist extension necessary for maximal action of flexors); Loss of sensation over posterior arm/forearm and dorsal hand

Question 27

Median Nerve (C5-T1)

Answer 27

Upper Extremity Nerve Causes of injury: Supracondylar fracture of humerus (proximal lesion); carpal tunnel syndrome and wrist laceration (distal lesion) Presentation: “Ape hand” and “Pope’s blessing”; Loss of wrist flexion, flexion of lateral fingers, thumb opposition, lumbricals of 2nd and 3rd digits; Loss of sensation over thenar eminence and dorsal and palmar aspects of lateral 31⁄2 fingers with proximal lesion; Tinel sign (tingling on percussion) in carpal tunnel syndrome

Question 28

Ulnar Nerve (C8-T1)

Answer 28

Upper extremity Nerve Causes of Injury: Fracture of medial epicondyle of humerus “funny bone” (proximal lesion); fractured hook of hamate (distal lesion) Presentation: “Ulnar claw” on digit extension; Radial deviation of wrist upon flexion (proximal lesion); Loss of wrist flexion, flexion of medial fingers, abduction and adduction of fingers (interossei), actions of medial 2 lumbrical muscles; Loss of sensation over medial 11/2 fingers including hypothenar eminence

Question 29

Recurrent branch of median nerve (C5-T1)

Answer 29

Upper extremity nerve causes of injury: Superficial laceration of palm Presentation: "Ape Hand"; Loss of thenar muscle group: opposition, abduction, and flexion of thumb; no loss of sensation

Question 30

RTDCB

Answer 30

Randy Travis Drinks Cold Beer | Roots Trunks Divisions Cords Branches

Question 31

Erb Palsy

Answer 31

"Waiter's Tip" Injury: Traction or tear of upper ("Erb-er") trunk: c5-c6 roots Causes: Infants - lateral traction on neck during delivery adults - trauma Muscle deficit: deltoid, supraspinatus --> functional deficit: abduction (arm hangs by side) Infraspinatus --> functional deficit: lateral rotation (arm medially rotated) Biceps Brachii --> functional deficit: Flexion, supination (arm extended and pronated)

Question 32

Klumpke palsy

Answer 32

Injury: Traction or tear of lower trunk: C8-T1 Causes: Infants - upward force on arm during delivery Adults - trauma (e.g., grabbing a tree branch to break a fall) Muscle deficit: Intrinsic hand muscles: lumbricals, interossei, thenar, hypothenar --> functional deficit: total claw hand: lumbricals normally flex MCP joints and extend DIP and PIP joints

Question 33

Thoracic outlet syndrome

Answer 33

Injury: compression of lower trunk and subclavian vessels Causes: Cervical rib, pancoast tumor Muscle Deficit: Same as Klumpke Palsy (Intrinsic hand muscles: lumbricals, interossei, thenar, hypothenar) --> Atrophy of intrinsic hand muscles; ischemia, pain, and edema due to vascular compression

Question 34

Winged Scapula

Answer 34

Injury: Lesion of long thoracic nerve Causes: Axillary node dissection after mastectomy, stab wounds Muscle deficit: Serratus anterior--> inability to anchor scapula to thoracic cage --> cannot abduct arm above horizontal position

Question 35

Distortions of the Hand

Answer 35

At rest, a balance exists between the extrinsic flexors and extensors of the hand, as well as the intrinsic muscles of the hand—particularly the lumbrical muscles (flexion of MCP, extension of DIP and PIP joints). “Clawing”—seen best with distal lesions of median or ulnar nerves. Remaining extrinsic flexors of the digits exaggerate the loss of the lumbricals --> Ž fingers extend at MCP, flex at DIP and PIP joints. Deficits less pronounced in proximal lesions; deficits present during voluntary flexion of the digits.

Question 36

"Ulnar claw"

Answer 36

3rd/4th fingers bent while 1st/2nd straight Context: while extending fingers or at rest Location of Lesion: distal ulnar nerve

Question 37

"Pope's Blessing"

Answer 37

3rd/4th fingers bent while 1st/2nd straight Context: while making a fist Location of lesion: proximal median nerve

Question 38

"Median Claw"

Answer 38

1st/2nd fingers bent while 3rd/4th straight Context: while extending fingers or at rest Location of lesion: distal median nerve

Question 39

"OK gesture"

Answer 39

digits 1-3 are flexed Context: While making fist Location of lesion: Proximal ulnar nerve

Question 40

Median Nerve Lesions

Answer 40

"pope's blessing," "median claw," and "ape's hand" (unopposable thumb) due to atrophy of the thenar eminence

Question 41

Ulnar Nerve Lesions

Answer 41

"OK gesture," "ulnar claw," and atrophy of the hypothenar eminence

Question 42

Hand Muscles

Answer 42

DAB = Dorsals ABduct PAD = Palmars ADduct Thenar (median) = Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis, superficial head (deep head by ulnar nerve). Hypothenar (ulnar) = Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis. -both groups perform the same functions: Oppose, Abduct, and Flex (OAF) Dorsal interossei—abduct the fingers. Palmar interossei—adduct the fingers. Lumbricals—flex at the MCP joint, extend PIP and DIP joints.

Question 43

Obturator Nerve (L2-L4)

Answer 43

Lower Extremity Nerve Cause of injury: Pelvic Surgery Presentation: decreased thigh sensation (medial) and decreased adduction

Question 44

Femoral Nerve (L2-L4)

Answer 44

Lower Extremity Nerve Cause of injury: Pelvic fracture Presentation: decreased thigh flexion and leg extension

Question 45

Common peroneal nerve (L4-S2)

Answer 45

Lower Extremity Nerve Cause of Injury: Trauma or compression of lateral aspect of leg, fibular neck fracture Presentation: Foot drop - inverted and plantarflexed at rest, loss of eversion and dorsiflexion. "Steppage Gait." Loss of sensation on dorsum of foot PED = Peroneal Everts and Dorsiflexes; if injured foot dropPED

Question 46

Tibial Nerve (L4-S3)

Answer 46

Lower Extremity Nerve Cause of injury: Knee trauma, Baker cyst (proximal lesion); tarsal tunnel syndrome (distal lesion) Presentation: Inability to curl toes and loss of sensation on sole of foot. In proximal lesions, foot everted at rest with loss of inversion and plantarflexion TIP = Tibial Inverts and Plantarflexes; if injured, can't stand on TIPtoes

Question 47

Superior gluteal nerve (L4-S1)

Answer 47

Lower extremity nerve Cause of injury: Iatrogenic injury during intramuscular injection to upper medial gluteal region Presentation: Trendelenburg sign/gait - pelvis tilts because weight-bearing leg cannot maintain alignment of pelvis through hip abduction. Lesion is contralateralto side of the hip that drops, ipsilateral to extremity on which the patient stands Innervates gluteus medius, gluteus minimus, and tensor fascia latae. Choose a superolateral gluteal quadrant as intramuscular injection site to avoid nerve injury.

Question 48

Inferior gluteal nerve (L5-S2)

Answer 48

Lower extremity Nerve Cause of injury: posterior hip dislocation Presentation: difficulty climbing stairs, rising from seated position. Loss of hip extension Innervates gluteus maximus.

Question 49

Sciatic nerve (L4-S3)

Answer 49

Innervates posterior thigh, splits into common peroneal and tibial nerves

Question 50

Pudendal nerve (S2-S4)

Answer 50

innervates perineum. Can be blocked with local anesthesia during childbirth using the ischial spine as a landmark for injection

Question 51

Signs of Lumbosacral Radiculopathy

Answer 51

(Disease involving the lumbar spinal nerve route, normally caused by compression) Paresthesias and weakness in distribution of specific lumbar or sacral spinal nerves. Often due to intervertebral disc herniation in which the nerve associated with the inferior vertebral body is impinged (e.g., herniation of L3-L4 disc affects the L4 spinal nerve) Disc Level --> Findings L3-L4 --> Weakness of knee extension, decreased patellar reflex L4-L5 --> Weakness of dorsiflexion, difficulty in heel-walking L5-S1 --> Weakness of plantarflexion, difficulty in toe-walking, decreased Achilles reflex

Question 52

Direction of Intervertebral Disc Herniation

Answer 52

Intervertebral discs generally herniate posterolaterally, due to the thin posterior longitudinal ligament and thicker anterior longitudinal ligament along the midline of the vertebral bodies.

Question 53

Axilla/Lateral thorax (name nerve and artery)

Answer 53

Long thoracic nerve | lateral thoracic artery

Question 54

Surgical neck of humerus (name nerve and artery)

Answer 54

Axillary Nerve | Posterior circumflex artery

Question 55

Midshaft of humerus (name nerve and artery)

Answer 55

Radial Nerve | Deep Brachial Artery

Question 56

Distal Humerus/cubital fossa (name nerve and artery)

Answer 56

Median Nerve | Brachial Artery

Question 57

Popliteal fossa (name nerve and artery)

Answer 57

Tibial Nerve | Popliteal Artery

Question 58

Posterior to medial malleolus (name nerve and artery)

Answer 58

Tibial Nerve | Posterior Tibial Artery

Question 59

Muscle Conduction to Contraction

Answer 59

T-tubules are extensions of plasma membrane juxtaposed with terminal cisternae of the sarcoplasmic reticulum. In skeletal muscle, 1 T-tubule + 2 terminal cisternae = triad. In cardiac muscle, 1 T-tubule + 1 terminal cisterna = dyad. 1. Action potential depolarization opens presynaptic voltage-gated Ca2+ channels, inducing neurotransmitter release. 2. Postsynaptic ligand binding leads to muscle cell depolarization in the motor end plate. 3. Depolarization travels along muscle cell and down the T-tubule. 4. Depolarization of the voltage-sensitive dihydropyridine receptor, mechanically coupled to the ryanodine receptor on the sarcoplasmic reticulum, induces a conformational change in both receptors, causing Ca2+ release from sarcoplasmic reticulum. 5. Released Ca2+ binds to troponin C, causing a conformational change that moves tropomyosin out of the myosin-binding groove on actin filaments. 6. Myosin releases bound ADP and Pi Ž--> displacement of myosin on the actin filament (power stroke). Contraction results in shortening of H and I bands and between Z lines (HIZ shrinkage), but the A band remains the same length (A band is Always the same length) A . 7. Binding of a new ATP molecule causes detachment of myosin head from actin filament. Hydrolysis of bound ATP -->Ž ADP, myosin head adopts high-energy position (“cocked”) for the next contraction cycle.

Question 60

Type 1 Muscle

Answer 60

Slow Twitch; red fibers resulting from increased [mito] and [Mb] (increased oxphos) --> sustained contraction. Proportion increases after endurance training. "1 slow red ox."

Question 61

Type 2 Muscle

Answer 61

Fast twitch; white fibers resulting from decreased [mito] and [Mb] (increased anaerobic glycolysis). Proportion increases after weight/resistance training.

Question 62

Endochondral Ossification

Answer 62

Bone formation. Bones of axial skeleton, appendicular skeleton, and base of skull. Cartilaginous model of bone is first made by chondrocytes. Osteoclasts and osteoblasts later replace with woven bone and then remodel to lamellar bone. In adults, woven bone occurs after fractures and in Paget disease. Defective in achondroplasia.

Question 63

Membranous Ossification

Answer 63

Bone formation. | Bones of calvarium and facial bones. Woven bone formed directly without cartilage. Later remodeled to lamellar bone.

Question 64

Osteoblast

Answer 64

Builds bone by secreting collagen and catalyzing mineralization in alkaline environment via ALP. Differentiates from mesenchymal stem cells in periosteum.

Question 65

Osteoclast

Answer 65

Dissolves bone by secreting H+ and collagenases. Differentiates from a fusion of monocyte/macrophage lineage precursors.

Question 66

Parathyroid hormone

Answer 66

At low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect). Chronically  PTH levels (1° hyperparathyroidism) cause catabolic effects (osteitis fibrosa cystica).

Question 67

Estrogen

Answer 67

``` Inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts. Estrogen deficiency (surgical or postmenopausal), excess cycles of remodeling, and bone resorption lead to osteoporosis. ```