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Musculoskeletal
92 entries across 8 regions · 416 questions
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Back
- Atlas and axis (C1 and C2)HY BoneThe first two cervical vertebrae, specialized for head movement. The atlas (C1) has no body; the axis (C2) carries the dens, around which the atlas rotates. Their fractures and instability are high-yield.
- Cauda equinaHY NerveBundle of lumbar and sacral nerve roots descending in the lumbar cistern below the end of the spinal cord. Compression causes cauda equina syndrome, a surgical emergency.
- Cervical vertebraeHY BoneSeven small vertebrae of the neck with transverse foramina for the vertebral arteries. Cervical radiculopathy, myelopathy and trauma clearance are the key clinical topics.
- Erector spinaeHY MuscleMain extensor of the vertebral column, running in three columns beside the spine. It is supplied by the dorsal rami of spinal nerves and is the usual site of mechanical low back strain.
- Intervertebral discHY JointFibrocartilaginous joint between vertebral bodies, made of a tough anulus fibrosus around a gel-like nucleus pulposus. Lumbar disc herniation at L4–L5 or L5–S1 causes sciatica.
- Latissimus dorsi MuscleBroad flat muscle of the lower back that extends, adducts and medially rotates the arm. It is supplied by the thoracodorsal nerve and forms the posterior axillary fold.
- Levator scapulae MuscleStrap-like muscle from the upper cervical transverse processes to the superior angle of the scapula. It elevates the scapula and is a frequent source of neck and shoulder stiffness.
- Lumbar vertebraeHY BoneFive large weight-bearing vertebrae of the lower back. Spondylolysis, spondylolisthesis and lumbar spinal stenosis are their key clinical problems.
- Rhomboid major and minor MuscleTwo flat muscles between the upper thoracic spine and the medial border of the scapula that retract the scapula. They are supplied by the dorsal scapular nerve (C5).
- Sacrum and coccyx BoneThe fused sacral vertebrae form the posterior wall of the pelvis and articulate with the ilia at the sacroiliac joints; the coccyx is the vestigial tail. The sacral hiatus is the route for caudal epidural block.
- Spinal nerves and rootsHY NerveThe 31 pairs of mixed nerves formed from dorsal (sensory) and ventral (motor) roots. Knowing where each root exits and what it supplies lets you localize radiculopathy.
- Suboccipital triangle Space / regionSmall triangle deep in the back of the neck, bounded by three suboccipital muscles. It contains the vertebral artery and the suboccipital nerve, and the greater occipital nerve emerges just below it.
- Thoracic vertebraeHY BoneTwelve vertebrae that articulate with the ribs. They are the common site of osteoporotic compression fractures, metastases and spinal tuberculosis.
- TrapeziusHY MuscleLarge superficial triangular muscle of the upper back and neck that elevates, retracts and rotates the scapula. It is supplied by the spinal accessory nerve (CN XI), whose injury causes a drooping shoulder and lateral winging.
- Triangle of auscultation and lumbar triangle Space / regionTwo gaps in the superficial muscles of the back. The triangle of auscultation lets breath sounds be heard clearly; the lumbar (Petit) triangle is a rare site of lumbar hernia.
- Vertebral columnHY BoneColumn of 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, about 4 coccygeal) with four curvatures. It supports the trunk, protects the spinal cord, and is the site of scoliosis, kyphosis and inflammatory back disease.
- Vertebral ligamentsHY LigamentLigaments that bind the vertebrae. The longitudinal ligaments run along the bodies and the ligamentum flavum joins the laminae; these are the layers a needle passes through during lumbar puncture and epidural anesthesia.
- Zygapophysial (facet) joints JointPaired synovial joints between the articular processes of adjacent vertebrae. Their orientation determines spinal motion at each level, and facet arthropathy is a common cause of axial back and neck pain.
Thorax
- Intercostal spaceHY Space / regionSpace between adjacent ribs containing three muscle layers and the intercostal neurovascular bundle, which runs along the lower border of the rib above.
- Pectoralis major MuscleLarge fan-shaped muscle of the anterior chest that adducts and medially rotates the arm. It forms the anterior axillary fold and lies deep to the breast.
- RibsHY BoneTwelve pairs of curved bones forming most of the thoracic cage. They are grouped as true, false and floating ribs, and rib fractures are the most common thoracic injury.
- SternumHY BoneFlat bone of the anterior thoracic wall made of the manubrium, body and xiphoid process. The sternal angle is the key surface landmark of the thorax.
Abdomen
- Anterior abdominal wallHY Space / regionLayered musculoaponeurotic wall from the costal margin to the pelvis. Its planes and regions are the map for describing abdominal pain, and it is the site of ventral hernias.
- Psoas major MuscleLong muscle beside the lumbar spine that joins iliacus to flex the hip. The lumbar plexus forms within it, and the psoas sign reflects inflammation of structures lying on it.
- Rectus abdominis MuscleLong strap muscle on either side of the linea alba, enclosed in the rectus sheath. It flexes the trunk, and hematoma in its sheath is a classic complication of anticoagulation.
Pelvis & Perineum
- Bony pelvisHY BoneRing formed by the two hip bones, the sacrum and the coccyx. Its inlet and outlet define the birth canal, and ring fractures from high-energy trauma can cause life-threatening hemorrhage.
- Hip boneHY BoneLarge flat bone formed by the fusion of the ilium, ischium and pubis at the acetabulum. Its palpable landmarks guide the exam, and its apophyses are classic sites of avulsion fractures in adolescents.
- Pelvic diaphragmHY MuscleFunnel-shaped muscular floor of the pelvis formed by levator ani and coccygeus. It supports the pelvic organs and maintains urinary and fecal continence; its weakening underlies pelvic organ prolapse and stress incontinence.
- Pubic symphysis JointFibrocartilaginous midline joint between the two pubic bones. It widens in pregnancy and after open-book pelvic injuries, and is a source of groin pain in athletes (osteitis pubis).
- Sacroiliac jointHY JointStrong, nearly immobile joint between the sacrum and ilium that transmits body weight to the pelvis. It is the classic site of inflammatory sacroiliitis in axial spondyloarthritis.
- Sacrotuberous and sacrospinous ligamentsHY LigamentTwo strong ligaments from the sacrum and coccyx to the ischium that stabilize the sacrum and turn the sciatic notches into the greater and lesser sciatic foramina, the gateways between pelvis, gluteal region and perineum.
Upper Limb
- AxillaHY Space / regionPyramidal space between the arm and the thoracic wall. It is the passageway for the neurovascular bundle of the upper limb and contains the axillary lymph nodes, which drain most of the breast.
- Axillary nerveHY NerveBranch of the posterior cord that passes through the quadrangular space around the surgical neck of the humerus to supply deltoid and teres minor.
- Biceps brachiiHY MuscleTwo-headed muscle of the anterior arm and the most powerful supinator of the forearm; it also flexes the elbow.
- Brachial plexusHY NerveNetwork formed by the ventral rami of C5–T1 that supplies the motor and most of the sensory innervation of the upper limb.
- Carpal tunnelHY Space / regionOsseofibrous tunnel on the palmar wrist, formed by the carpal bones and the flexor retinaculum, that carries the median nerve and nine long flexor tendons.
- ClavicleHY BoneS-shaped strut connecting the upper limb to the axial skeleton; one of the most commonly fractured bones, usually in its middle third.
- Cubital fossaHY Space / regionTriangular depression on the anterior elbow containing the biceps tendon, brachial artery and median nerve. It is the usual site for venipuncture and blood pressure auscultation.
- DeltoidHY MuscleTriangular muscle that forms the rounded contour of the shoulder. It is the main abductor of the arm beyond the first ~15° and is supplied by the axillary nerve.
- Elbow jointHY JointHinge joint between the humerus, ulna and radius. It shares a capsule with the proximal radioulnar joint and is the site of common overuse and pediatric injuries.
- Glenohumeral jointHY JointBall-and-socket joint between the humeral head and the glenoid cavity. It is the most mobile joint in the body and the most frequently dislocated major joint.
- HumerusHY BoneLong bone of the arm. It articulates with the scapula at the shoulder and with the radius and ulna at the elbow, and four major nerves lie against it at predictable fracture sites.
- InfraspinatusHY MuscleRotator cuff muscle in the infraspinous fossa and the main lateral (external) rotator of the arm.
- Long thoracic nerveHY NerveBranch arising directly from the C5–C7 roots that supplies serratus anterior; injury causes medial winging of the scapula.
- Median nerveHY NerveFormed by roots from the lateral and medial cords. It supplies most of the anterior forearm and the thenar muscles, and passes through the carpal tunnel.
- Musculocutaneous nerve NerveLateral cord branch that pierces coracobrachialis, supplies the anterior arm muscles, and ends as the lateral cutaneous nerve of the forearm.
- Pronator teres MuscleSuperficial muscle of the anterior forearm. It pronates the forearm, forms the medial border of the cubital fossa, and the median nerve passes between its two heads.
- Radial nerveHY NerveLargest branch of the brachial plexus (posterior cord). It supplies all extensor muscles of the arm and forearm and winds around the humerus in the radial groove.
- RadiusHY BoneLateral bone of the forearm. It rotates around the ulna in pronation and supination, and its distal end is one of the most commonly fractured sites in the body.
- ScaphoidHY BoneBoat-shaped bone of the proximal carpal row. It is the most commonly fractured carpal bone and its proximal pole is prone to avascular necrosis.
- ScapulaHY BoneTriangular flat bone on the posterolateral thorax that gives attachment to the rotator cuff and forms the glenoid cavity of the shoulder joint.
- Serratus anteriorHY MuscleSerrated muscle on the lateral thoracic wall that protracts the scapula, rotates it upward, and holds it against the chest wall.
- SubscapularisHY MuscleLarge rotator cuff muscle on the costal surface of the scapula. It is the main medial rotator of the arm and the only cuff muscle inserting on the lesser tubercle.
- SupraspinatusHY MuscleRotator cuff muscle in the supraspinous fossa that initiates abduction and is the most commonly torn cuff tendon.
- Teres minor MuscleSmall rotator cuff muscle from the lateral border of the scapula. It laterally rotates the arm and is supplied by the axillary nerve.
- Triceps brachii MuscleThree-headed muscle of the posterior arm and the chief extensor of the elbow; supplied by the radial nerve.
- Ulna BoneMedial, stabilizing bone of the forearm. Its trochlear notch forms the hinge of the elbow with the humerus.
- Ulnar nerveHY NerveMedial cord branch that passes behind the medial epicondyle and through Guyon's canal. It supplies most intrinsic hand muscles and the medial 1½ digits.
- Wrist jointHY JointCondyloid joint between the distal radius (and articular disc) and the proximal carpal row. It's a common site of fractures, instability and tenosynovitis.
Lower Limb
- Adductor muscles of the thigh MuscleMedial compartment muscles — adductor longus, brevis and magnus, gracilis, pectineus and obturator externus — that adduct the hip. They are supplied mostly by the obturator nerve, and adductor strains are the classic "groin pull".
- Ankle jointHY JointHinge joint in which the talus sits in a mortise formed by the tibia and fibula. Sprains of the lateral ligaments and malleolar fractures are extremely common; the Ottawa rules decide who needs an X-ray.
- Bones of the footHY BoneSeven tarsals, five metatarsals and fourteen phalanges forming the arches of the foot. Fifth metatarsal fractures, calcaneal fractures, stress fractures and plantar fasciitis are the common problems.
- Collateral ligaments of the kneeHY LigamentSide ligaments of the knee — the broad MCL, attached to the medial meniscus, resists valgus stress; the cord-like LCL resists varus stress. The MCL is the most commonly injured knee ligament.
- Common fibular nerveHY NerveLateral terminal branch of the sciatic nerve that winds around the fibular neck — the most commonly injured nerve of the lower limb. Injury causes foot drop and numbness of the dorsum of the foot.
- Compartments of the legHY Space / regionFour tight osteofascial compartments — anterior, lateral, superficial posterior and deep posterior — each with its own muscles, nerve and vessels. Rising pressure after fractures or crush injuries causes compartment syndrome, a surgical emergency.
- Cruciate ligamentsHY LigamentCrossed intra-articular ligaments of the knee that prevent the tibia sliding forward (ACL) or backward (PCL) on the femur. ACL tears from non-contact pivoting are among the most common serious sports injuries.
- Femoral nerveHY NerveLargest branch of the lumbar plexus (L2–L4), supplying the hip flexors and knee extensors and the skin of the anterior thigh and medial leg. Lesions cause knee buckling and a lost patellar reflex.
- Femoral triangleHY Space / regionTriangular region of the upper anterior thigh containing the femoral nerve, artery, vein and canal. It is the site of the femoral pulse, arterial and venous access, and femoral hernias.
- FemurHY BoneThe longest and strongest bone in the body. Femoral neck fractures in older adults, slipped capital femoral epiphysis and avascular necrosis of the head are its high-yield problems.
- FibulaHY BoneSlender lateral bone of the leg that bears little weight but forms the lateral malleolus of the ankle. The common fibular nerve wraps around its neck, where fractures and pressure injure it.
- Gluteus maximus MuscleThe largest and most superficial gluteal muscle, the main extensor of the hip for rising, climbing and running. Weakness from an inferior gluteal nerve lesion causes a backward-lurching gait.
- Gluteus medius and minimusHY MuscleFan-shaped hip abductors that keep the pelvis level when standing on one leg. Weakness or superior gluteal nerve injury produces the Trendelenburg sign; their tendons cause lateral hip pain.
- HamstringsHY MusclePosterior thigh muscles — biceps femoris, semitendinosus and semimembranosus — that extend the hip and flex the knee. Hamstring strains are common in sprinting sports.
- Hip jointHY JointDeep ball-and-socket joint between the femoral head and the acetabulum, built for stability. Osteoarthritis, posterior dislocation, septic arthritis in children and developmental dysplasia are the high-yield topics.
- Knee jointHY JointThe largest synovial joint — a modified hinge between the femur, tibia and patella, stabilized mainly by ligaments and the menisci. Ligament and meniscal injuries, effusions and osteoarthritis make it one of the most examined joints.
- Lateral ankle ligamentsHY LigamentThree ligaments from the lateral malleolus — anterior talofibular, calcaneofibular and posterior talofibular — that resist inversion. The ATFL is the most commonly injured ligament in the body.
- Menisci of the kneeHY LigamentTwo crescent-shaped fibrocartilage pads on the tibial plateau that deepen the articular surfaces, spread load and absorb shock. Tears — traumatic in the young, degenerative in older adults — cause joint-line pain, catching and locking.
- Obturator nerve NerveLumbar plexus branch (L2–L4) that runs along the lateral pelvic wall through the obturator canal to supply the hip adductors and a patch of medial thigh skin. It is injured in pelvic surgery and childbirth.
- PatellaHY BoneThe largest sesamoid bone, embedded in the quadriceps tendon in front of the knee. It increases the leverage of the quadriceps and is involved in patellofemoral pain, dislocation and fractures.
- Piriformis MusclePear-shaped lateral rotator of the hip and the key landmark of the gluteal region — structures leave the pelvis above or below it. It can irritate the sciatic nerve (piriformis syndrome).
- Popliteal fossaHY Space / regionDiamond-shaped space behind the knee containing the popliteal vessels, the tibial and common fibular nerves and lymph nodes. Baker cysts, popliteal aneurysms and knee-dislocation vascular injury arise here.
- Quadriceps femorisHY MuscleFour-headed extensor of the knee in the anterior thigh, supplied by the femoral nerve. It tests the L4 reflex, and its tendon, patella and patellar ligament form the knee's extensor mechanism.
- Sciatic nerveHY NerveThe largest nerve in the body (L4–S3), running from the buttock down the back of the thigh and dividing into the tibial and common fibular nerves. It supplies the hamstrings and everything below the knee except a strip of skin on the medial leg.
- TibiaHY BoneThe weight-bearing medial bone of the leg. Its subcutaneous shaft makes open fractures and compartment syndrome common, and the tibial tuberosity is the site of Osgood–Schlatter disease.
- Tibial nerveHY NerveLarger terminal branch of the sciatic nerve, running through the popliteal fossa and deep posterior leg to the sole. It supplies the plantarflexors and inverters and the skin of the sole, and is compressed in the tarsal tunnel.
- Triceps surae and calcaneal tendonHY MuscleGastrocnemius and soleus form the calf and insert via the Achilles tendon on the calcaneus to plantarflex the ankle. They carry the S1 ankle reflex; Achilles rupture and tendinopathy are common.
Head & Neck
- Mandible BoneThe lower jaw — the largest facial bone and the only movable bone of the skull. As a ring with the skull base, it often fractures in two places, and the inferior alveolar nerve runs through it.
- Muscles of masticationHY MuscleFour muscles derived from the first pharyngeal arch and supplied by the mandibular nerve (V3) — masseter, temporalis and medial pterygoid close the jaw; lateral pterygoid opens and protrudes it.
- SkullHY BoneThe bones of the head — the neurocranium enclosing the brain and the viscerocranium forming the face. Pterion fractures, basilar skull fractures and infant fontanelles are the clinically important features.
- SternocleidomastoidHY MuscleProminent two-headed neck muscle that divides the neck into anterior and posterior triangles. It is supplied by the accessory nerve and is shortened in congenital muscular torticollis.
- Temporomandibular joint JointSynovial joint between the mandibular condyle and the temporal bone, divided by an articular disc into two compartments that allow hinging and gliding. TMJ disorders and anterior dislocation are common.