Page 504 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

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pathology
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460 section iii Musculoskeletal, skin, and connective tissue ` pathology Musculoskeletal, skin, and connective tissue ` pathology

Clavicle fractures Common in children and as birth trauma. Usually caused by a fall on outstretched hand or by
direct trauma to shoulder. Weakest point at the junction of middle and lateral thirds; fractures at
the middle third segment are most common. Presents as shoulder drop, shortened clavicle (lateral
fragment is depressed due to arm weight and medially rotated by arm adductors [eg, pectoralis
major]).

Common hip and knee conditions
“Unhappy triad” Common injury in contact sports due to lateral
force applied to a planted foot. Consists of
damage to the ACL A , MCL, and medial Lateral force
meniscus (attached to MCL). However, lateral PCL ACL
meniscus involvement is more common than
medial meniscus involvement in conjunction LCL
with ACL and MCL injury. Presents with
acute pain and signs of joint instability.

MM

MCL LM
Anterior view of left knee
Prepatellar bursitis Inflammation of the prepatellar bursa in front of
the kneecap (red arrow in B ). Can be caused
by repeated trauma or pressure from excessive
kneeling (also called “housemaid’s knee”).
Baker cyst Popliteal fluid collection (red arrow in C )
in gastrocnemius-semimembranosus bursa
commonly communicating with synovial
space and related to chronic joint disease (eg,
osteoarthritis, rheumatoid arthritis).
A B C

Fem
Fem Fem Fem
Pat
(lat cond) (med cond)

ACL Tib Post meniscus
Ant meniscus
Tib Pop a

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