Clinical imaging: Musculoskeletal and trauma imaging

🩻 Musculoskeletal and trauma imaging — page 5 of the Clinical Imaging chapter. Bone and joint X-rays are among the commonest films interpreted by front-line doctors — often in the ED before a radiologist sees them — and missed fractures (scaphoid, hip, posterior shoulder dislocation, cervical spine in older people) are a frequent source of harm. This page covers how to describe fractures, the decision rules that tell you who needs a film, the patterns of arthritis and bone disease, and imaging in major trauma.
Your four questions for every musculoskeletal image: Do I have two views at right angles, and the joints above and below? Is there a fracture or dislocation — and is it stable, open, or involving a joint or growth plate? If the film is normal but the clinical suspicion is high, what's the next test? Could this be a pathological fracture or non-accidental injury?

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Principles of Musculoskeletal Imaging

• Plain X-ray first for most bone injuries and bone pain.
• Rule of twos:
  • Two views at right angles (e.g. AP and lateral) — a fracture or dislocation can be invisible on one view.
  • Two joints — include the joint above and below for long bone fractures (e.g. Maisonneuve, Monteggia, Galeazzi injuries).
  • Two sides — compare with the other side in children (ossification centres).
  • Two occasions — repeat films at 10–14 days for occult fractures (scaphoid), or use MRI.
• Clinical decision rules reduce unnecessary films — Ottawa ankle and knee rules, Canadian C-spine rule.
• CT — complex and intra-articular fractures (tibial plateau, calcaneus, acetabulum, pelvis), spine, surgical planning; occult fractures when MRI isn't available.
• MRI — occult fractures (hip, scaphoid, stress fractures), ligaments, menisci, cartilage, tendons, bone marrow (osteomyelitis, tumours, avascular necrosis), spinal cord.
• Ultrasound — tendons, muscles, joint effusions (guided aspiration), soft tissue lumps, foreign bodies, infant hips.
• Nuclear medicine — bone scan (metastases, stress fractures, occult fractures when MRI isn't possible); PET-CT (sarcoma staging, infection in selected cases).
• Look beyond the fracture — bone density, lytic lesions (pathological fracture), soft tissue swelling, joint effusion (fat pads, lipohaemarthrosis), foreign bodies.

Describing a Fracture

• Patient and film — name, date, views, side.
• Bone and location — which bone; diaphysis (shaft), metaphysis, epiphysis; proximal, middle or distal third; intra-articular or extra-articular.
• Pattern:
  • Transverse (direct blow), oblique, spiral (twisting — in a non-mobile child, consider NAI).
  • Comminuted (more than two fragments), segmental, butterfly fragment.
  • Avulsion (tendon or ligament pulls off bone — e.g. base of the fifth metatarsal).
  • Impacted, compression (vertebral body), stress fracture, pathological (through abnormal bone — tumour, metastasis, Paget's).
• Displacement — translation (as % of bone width), angulation (direction of the distal fragment's apex — e.g. dorsal angulation), rotation (often clinical), shortening, distraction.
• Joint involvement — intra-articular step, dislocation or subluxation.
• Open or closed — any wound over a fracture is open until proven otherwise (antibiotics within 1 hour, tetanus, photograph, cover — BOAST).
• Soft tissue and neurovascular status — document distal pulses, sensation and movement before and after manipulation.
• Example — "AP and lateral X-rays of the left wrist show a transverse extra-articular fracture of the distal radial metaphysis with dorsal angulation of 25° and dorsal displacement, consistent with a Colles' fracture."

Children's Fractures and Safeguarding

• Children's bones are softer, with growth plates (physes) — different fracture patterns:
  • Buckle (torus) — bulging of the cortex (distal radius) — stable — removable splint, no routine follow-up X-ray (NICE NG38).
  • Greenstick — one cortex breaks, the other bends.
  • Plastic deformation — bowing without a visible fracture line.
• Salter–Harris classification (growth plate injuries) — "SALTR":

  Type	Description	Notes
  I — Straight	Through the physis only	X-ray may look normal (widened physis)
  II — Above	Physis plus metaphysis	Commonest; good prognosis
  III — Lower	Physis plus epiphysis (intra-articular)	Needs accurate reduction
  IV — Through	Metaphysis, physis and epiphysis	Growth disturbance risk
  V — Rammed	Crush of the physis	Often missed; worst prognosis

• Suspected physical abuse (non-accidental injury) — fractures suggesting abuse:
  • Any fracture in a non-mobile infant (not yet crawling or walking).
  • Metaphyseal corner ("bucket handle") fractures, posterior rib fractures (squeezing), scapular, sternal and spinous process fractures, complex skull fractures.
  • Multiple fractures of different ages (healing stages).
  • History inconsistent with the injury or developmental stage; delayed presentation.
• Imaging for suspected abuse (RCR/SCoR guidance) — skeletal survey in children under 2 (and selected older children), repeat limited survey at 11–14 days (healing fractures become visible); CT head in infants under 1 (and considered in under 2s) — subdural haematomas, skull fractures; ophthalmology (retinal haemorrhages); follow local safeguarding procedures.
• Differentials — osteogenesis imperfecta, rickets, birth injury, accidental injury, leukaemia.

Shoulder and Elbow

• Anterior shoulder dislocation (about 95%) — fall on an outstretched or abducted, externally rotated arm — humeral head lies anterior and inferior to the glenoid (below the coracoid) on AP; confirm on a lateral (Y or axial) view; associated Hill–Sachs lesion (humeral head impaction) and Bankart lesion (anterior glenoid labrum or bone); check axillary nerve (regimental badge sensation) before and after reduction; post-reduction X-ray.
• Posterior shoulder dislocation — seizures, electric shock, direct blow — often missed on AP: "lightbulb" sign (internally rotated humeral head), widened glenohumeral space, axial or Y view essential.
• Proximal humerus fractures — older people after falls (osteoporosis); clavicle fractures (middle third commonest); acromioclavicular joint injuries.
• Elbow:
  • Fat pad signs — a visible posterior fat pad (or a raised "sail-shaped" anterior fat pad) indicates an effusion — assume an occult fracture (adults — radial head; children — supracondylar).
  • Supracondylar fracture (children, fall on outstretched hand) — the anterior humeral line should pass through the middle third of the capitellum (passes anterior in extension-type fractures) — check brachial artery and median, radial and ulnar nerves (anterior interosseous nerve); compartment syndrome risk.
  • Ossification centres (approximate age in years) — "CRITOE": Capitellum 1, Radial head 3, Internal (medial) epicondyle 5, Trochlea 7, Olecranon 9, External (lateral) epicondyle 11 — an "ossification centre" seen out of order may be an avulsed medial epicondyle trapped in the joint.
  • Radiocapitellar line — a line along the radial shaft should pass through the capitellum on every view — if not, radial head dislocation.
  • Monteggia — proximal ulna fracture with radial head dislocation; Galeazzi — distal radius fracture with distal radioulnar joint dislocation ("MUGR" — Monteggia Ulna, Galeazzi Radius).
  • Pulled elbow (radial head subluxation — toddlers) — X-ray not needed if typical history and reduction works.

Wrist and Hand

• Distal radius fractures:
  • Colles' — extra-articular distal radius fracture with dorsal angulation ("dinner fork") — fall on outstretched hand — postmenopausal women (osteoporosis).
  • Smith's — volar angulation (fall on a flexed wrist).
  • Barton's — intra-articular fracture of the dorsal or volar rim with carpal subluxation.
  • Assess radial height, inclination and volar tilt; DEXA and fracture liaison referral in older people.
• Scaphoid fracture:
  • Young adults — fall on outstretched hand — anatomical snuffbox tenderness, scaphoid tubercle tenderness, pain on axial thumb compression.
  • Scaphoid series (4 views) — up to 1 in 5 fractures are not visible initially.
  • Clinically suspected with normal X-rays — immobilise and arrange early MRI (preferred — RCEM/BSSH pathways) or CT; or repeat X-ray at 10–14 days.
  • Complications — avascular necrosis of the proximal pole (retrograde blood supply), non-union, arthritis.
• Carpal dislocations — lunate and perilunate dislocations — "spilled teacup" on the lateral view; median nerve symptoms — easily missed — urgent orthopaedics.
• Scapholunate dissociation — gap over 3 mm ("Terry Thomas" sign).
• Hand — boxer's fracture (fifth metacarpal neck — check for fight bite wounds over the knuckle — antibiotics and washout), Bennett's fracture (intra-articular base of first metacarpal — unstable), mallet finger (avulsion at the distal phalanx base), gamekeeper's thumb (ulnar collateral ligament — Stener lesion), volar plate avulsions.

Hip and Pelvis

• Hip fracture — older people after a fall — pain, inability to weight-bear, shortened and externally rotated leg.
  • X-rays — AP pelvis and lateral hip; look at Shenton's line (smooth arc from the inferior femoral neck to the superior pubic ramus — disrupted in displaced fractures), trabecular pattern, cortical outline.
  • Intracapsular (subcapital, transcervical — Garden I–IV) — blood supply to the head at risk — undisplaced: screw fixation (or arthroplasty in older people); displaced: hemiarthroplasty or total hip replacement.
  • Extracapsular (intertrochanteric, subtrochanteric) — dynamic hip screw or intramedullary nail.
  • Occult hip fracture — if suspected despite negative X-rays, MRI (NICE CG124); if MRI isn't available within 24 hours or is contraindicated — CT.
  • Surgery — on the day of or the day after admission (NICE CG124); also look for pubic rami and acetabular fractures.
• Pelvic fractures:
  • Low-energy (older people) — pubic rami fractures — often occult; CT or MRI if pain persists and X-rays are normal; associated sacral insufficiency fractures.
  • High-energy — the pelvis is a ring — usually breaks in two places; open-book (anteroposterior compression), lateral compression, vertical shear — major haemorrhage risk — pelvic binder before imaging in unstable patients; CT; interventional radiology (embolisation) or surgical packing.
  • Acetabular fractures — CT for planning.
• Hip dislocation — usually posterior (knee hits the dashboard) — leg shortened, flexed, adducted and internally rotated — sciatic nerve injury; reduce urgently (avascular necrosis risk).
• Avascular necrosis of the femoral head — steroids, alcohol, sickle cell disease, previous fracture — MRI (early), later X-ray (crescent sign, collapse).

Knee, Ankle and Foot

• Ottawa knee rule — X-ray if any of: age 55 or over, isolated patella tenderness, fibular head tenderness, inability to flex to 90°, inability to bear weight (4 steps) immediately and in the ED.
• Knee X-ray signs:
  • Lipohaemarthrosis — fat–fluid level on a horizontal-beam lateral — intra-articular fracture (e.g. tibial plateau — CT).
  • Segond fracture — small avulsion from the lateral tibial plateau — strongly associated with ACL rupture.
  • Patellar fractures (vs bipartite patella — superolateral, smooth, often bilateral).
• MRI knee — ligament (ACL, PCL, collaterals) and meniscal tears, bone bruising, cartilage; not needed for degenerative knee pain in older adults.
• Ottawa ankle rules — ankle X-ray if pain in the malleolar zone and any of: bone tenderness at the posterior edge or tip of the lateral or medial malleolus (distal 6 cm), or inability to bear weight both immediately and in the ED (4 steps). Foot X-ray if midfoot pain and tenderness at the base of the fifth metatarsal or the navicular, or inability to bear weight.
• Ankle fractures — Weber classification (lateral malleolus relative to the syndesmosis):
  • Weber A — below the syndesmosis — usually stable — boot and weight-bear.
  • Weber B — at the level of the syndesmosis — may be unstable (check medial clear space, medial malleolus, weight-bearing films).
  • Weber C — above the syndesmosis — syndesmosis disrupted — unstable — surgical fixation.
  • Bimalleolar and trimalleolar fractures, talar shift — unstable; fracture-dislocation — reduce immediately (skin and neurovascular compromise) before X-ray if limb-threatening.
  • Maisonneuve fracture — medial ankle injury with a proximal fibular fracture — examine and image the whole fibula.
• Foot — fifth metatarsal base (avulsion — usually heals well) vs Jones fracture (proximal diaphysis — poor healing), Lisfranc injury (tarsometatarsal — easily missed — weight-bearing films or CT), calcaneal fractures (falls from height — Böhler's angle under 20°; look for spinal fractures), stress fractures (metatarsals — MRI or repeat X-ray).
• Achilles tendon rupture — clinical (Simmonds' test); ultrasound if uncertain.

Thoracolumbar Spine

• Osteoporotic vertebral fractures — the commonest osteoporotic fracture — often painless or minor trauma; anterior wedge or biconcave deformity, height loss, kyphosis; often unreported on chest X-ray or CT — FRAX, DEXA and bone protection; MRI (STIR) distinguishes acute from old fractures and from malignancy.
• Red flags for pathological fracture — cancer history, weight loss, night pain, posterior element involvement, soft tissue mass, involvement above T4 — MRI.
• Traumatic fractures:
  • Burst fracture — axial load (falls from height) — retropulsed fragments into the canal — CT and MRI.
  • Chance fracture — flexion-distraction (lap seatbelt) — horizontal fracture through the vertebra — associated abdominal (bowel, pancreas) injuries.
  • Three-column concept — injury to two or more columns is unstable.
  • Calcaneal fractures after falls — look for thoracolumbar fractures too.
• Ankylosing spondylitis and DISH — rigid spine fractures are unstable and easily missed — CT (whole spine) after any trauma.
• Spondylolysis and spondylolisthesis — pars defect ("Scottie dog collar" on oblique films) — adolescents in sport; slip grading.
• Discitis and vertebral osteomyelitis — MRI with contrast (see page 4).
• Non-specific back pain — no routine imaging (NICE NG59).

Arthritis on X-ray

Condition	X-ray features	Typical sites
Osteoarthritis	"LOSS" — Loss of joint space (asymmetric), Osteophytes, Subchondral sclerosis, Subchondral cysts	Knees, hips, DIP (Heberden's) and PIP (Bouchard's), first CMC, spine
Rheumatoid arthritis	"LESS" — Loss of joint space (symmetric), Erosions (periarticular, marginal), Soft tissue swelling, Soft (periarticular osteopenic) bones; later subluxation, ulnar deviation	MCPs, PIPs, wrists, MTPs (symmetric); atlantoaxial subluxation
Gout	"Punched-out" erosions with overhanging edges, preserved joint space until late, soft tissue tophi; dual-energy CT shows urate	First MTP (podagra), midfoot, ankle, hands, elbows
CPPD (pseudogout)	Chondrocalcinosis (calcified cartilage — knee menisci, triangular fibrocartilage of the wrist)	Knees, wrists, symphysis pubis
Psoriatic arthritis	Erosions with new bone formation, "pencil-in-cup" deformity, DIP involvement, dactylitis, periostitis, arthritis mutilans	DIPs, asymmetric; spine and SIJs
Ankylosing spondylitis	Sacroiliitis (bilateral, symmetric — erosions, sclerosis, fusion), syndesmophytes, "bamboo spine", squaring of vertebrae; MRI shows early sacroiliitis (bone marrow oedema)	Sacroiliac joints, spine
Septic arthritis	Often normal early (effusion); later rapid joint space loss and erosions	Knee, hip — aspirate
Charcot (neuropathic) joint	Destruction, fragmentation, dislocation, debris	Diabetic midfoot

• Early inflammatory arthritis — X-rays may be normal; ultrasound (synovitis, power Doppler) and MRI detect early disease.
• Knee OA in over-45s with typical symptoms — clinical diagnosis without imaging (NICE NG226); X-ray if atypical or before referral for surgery.

Bone Tumours and Aggressive Lesions

• Features of an aggressive (likely malignant) bone lesion:
  • Wide zone of transition (ill-defined margin) — permeative or moth-eaten bone destruction.
  • Aggressive periosteal reaction — Codman's triangle, sunburst (spiculated), "onion skin" (lamellated).
  • Cortical destruction and a soft tissue mass.
  • Rapid growth, pain at night.
• Benign features — narrow zone of transition, sclerotic rim, no or solid periosteal reaction, no soft tissue mass.
• Primary bone tumours:

  Tumour	Features
  Osteosarcoma	Teenagers (and older adults with Paget's); metaphysis around the knee; sunburst and Codman's triangle; lung metastases
  Ewing sarcoma	Children and teenagers; diaphysis of long bones and pelvis; "onion skin" periosteal reaction; fever and raised inflammatory markers (mimics infection)
  Chondrosarcoma	Older adults; pelvis, femur, shoulder; "rings and arcs" chondroid calcification
  Giant cell tumour	Young adults (20–40); epiphyseal, eccentric, lytic "soap bubble" lesion extending to the joint surface (around the knee)
  Osteoid osteoma	Young people; night pain relieved by NSAIDs; small lucent nidus with dense surrounding sclerosis — CT; radiofrequency ablation
  Simple bone cyst	Children; proximal humerus or femur; "fallen fragment" sign after pathological fracture
  Enchondroma	Hand bones; lytic with chondroid calcification; Ollier's disease (multiple)
  Non-ossifying fibroma	Children; eccentric metaphyseal lucency with a sclerotic border — benign "don't touch" lesion

• Suspected bone sarcoma (NICE NG12) — urgent X-ray within 48 hours for children and young people with unexplained bone swelling or pain; if the X-ray suggests sarcoma — very urgent referral (within 48 hours) to a specialist sarcoma service; don't biopsy outside the sarcoma centre (contaminates the surgical field).
• Night pain or persistent bone pain in a young person needs an X-ray — don't label it "growing pains" without examination.

Metastases, Myeloma and Metabolic Bone Disease

• Bone metastases — far more common than primary bone tumours in adults:
  • Lytic — kidney, thyroid, lung, breast, melanoma; sclerotic — prostate, breast (often mixed), carcinoid.
  • Sites — spine, pelvis, ribs, proximal femur and humerus.
  • Imaging — bone scan (sensitive for sclerotic metastases — prostate, breast), CT, MRI (spine, marrow), PSMA or FDG PET-CT.
  • Impending pathological fracture — lytic lesion over 2/3 of cortical width, pain on weight-bearing (Mirels' score) — prophylactic fixation and radiotherapy.
• Myeloma — multiple lytic "punched-out" lesions (skull — "pepper pot"), diffuse osteopenia, vertebral collapse; bone scan is often normal ("cold") — use whole-body low-dose CT or whole-body MRI (NICE NG35).
• Paget's disease — older adults; raised ALP with normal calcium; X-ray — thickened cortex, coarse trabeculae, bone enlargement, "cotton wool" skull, osteoporosis circumscripta, bowed tibia; bone scan — intense uptake; complications — deafness, fractures, osteosarcoma (rare); IV zoledronic acid for bone pain.
• Osteoporosis — DEXA (T-score −2.5 or less; −1 to −2.5 osteopenia); X-ray osteopenia is unreliable.
• Osteomalacia and rickets — Looser's zones (pseudofractures — lucent bands perpendicular to the cortex — pubic rami, femoral neck, scapula); rickets — cupping and fraying of metaphyses, widened growth plates, bowed legs, "rachitic rosary".
• Hyperparathyroidism — subperiosteal resorption (radial side of middle phalanges), "salt and pepper" skull, brown tumours, chondrocalcinosis.
• Renal osteodystrophy — "rugger jersey" spine (sclerotic end plates), vascular calcification.
• Sickle cell disease — avascular necrosis, bone infarcts, "H-shaped" vertebrae, osteomyelitis (Salmonella).

Bone and Joint Infection

• Septic arthritis — hot, swollen, painful joint with restricted movement — joint aspiration before antibiotics (ultrasound-guided for the hip and deep joints) — don't delay for imaging; X-ray is often normal early but provides a baseline (and excludes fracture or chondrocalcinosis).
• Acute osteomyelitis:
  • X-ray changes appear after 10–14 days (periosteal reaction, lytic destruction, sequestrum and involucrum in chronic disease) — a normal early X-ray doesn't exclude it.
  • MRI is the most sensitive and specific test (marrow oedema, abscess, extent); bone scan or white cell scan if MRI isn't possible.
  • Children — haematogenous spread to metaphyses (Staph aureus, Kingella in under-4s).
• Diabetic foot osteomyelitis (NICE NG19) — X-ray first; MRI if osteomyelitis is suspected and X-ray doesn't confirm it; probe-to-bone test; bone biopsy for microbiology.
• Prosthetic joint infection — X-ray (loosening, lucency), aspiration (orthopaedic team), nuclear medicine in selected cases.
• Necrotising fasciitis — surgery shouldn't wait for imaging; CT may show gas in the soft tissues and fascial fluid.
• Foreign bodies — glass and metal are usually visible on X-ray; wood and plastic often aren't — ultrasound.

The Child's Hip

• Developmental dysplasia of the hip (DDH) — risk factors (breech presentation, first-degree family history) or abnormal examination (Barlow, Ortolani) — ultrasound in infants under about 4–5 months (NIPE screening — by 6 weeks if risk factors, within 2 weeks if abnormal examination); X-ray once the femoral head ossifies (after about 4–6 months).
• Transient synovitis (irritable hip) — age 3–8, after a viral illness, well child, limp — ultrasound shows effusion but can't distinguish from septic arthritis.
• Septic arthritis of the hip — fever, unable to weight-bear, raised CRP and WCC (Kocher criteria) — urgent ultrasound-guided aspiration and orthopaedics.
• Perthes disease — boys aged 4–8 — avascular necrosis of the femoral head — limp, hip or knee pain — X-ray: flattened, fragmented, sclerotic femoral head; MRI early.
• Slipped upper femoral epiphysis (SUFE) — overweight adolescent boys (10–15), hip or knee pain, limp, loss of internal rotation — AP and frog-leg lateral X-rays of both hips — Klein's line (along the superior femoral neck) fails to intersect the epiphysis; bilateral in up to a third — urgent surgical pinning.
• Knee pain in a child — always examine (and image if needed) the hip.
• Other — Osgood–Schlatter (tibial tuberosity — clinical), osteomyelitis, leukaemia (bone pain, cytopenias), bone tumours.

Soft Tissue Imaging — Ultrasound and MRI

• Ultrasound:
  • Rotator cuff tears and tendinopathy, subacromial bursitis — and guided injections.
  • Tendon ruptures (Achilles, quadriceps, biceps), muscle tears and haematomas.
  • Joint effusions and synovitis; guided aspiration.
  • Soft tissue lumps — lipoma, ganglion, Baker's cyst (and rupture — mimics DVT; scan both), abscess, foreign bodies, Morton's neuroma.
  • Soft tissue sarcoma (NICE NG12) — urgent direct-access ultrasound (within 2 weeks) for adults with an unexplained lump that is increasing in size; refer on a suspected cancer pathway if the scan suggests sarcoma or is uncertain; red flags — over 5 cm, deep to fascia, growing, painful, recurrent after excision.
• MRI:
  • Knee — menisci, cruciate ligaments, cartilage, bone bruising.
  • Shoulder — labral tears (MR arthrogram), rotator cuff.
  • Hip — labral tears, femoroacetabular impingement, avascular necrosis, occult fractures.
  • Wrist — occult scaphoid fractures, ligament injuries.
  • Bone marrow — stress fractures, bone bruises, osteomyelitis, tumour infiltration.
  • Inflammatory — sacroiliitis in axial spondyloarthritis, myositis (guides biopsy), enthesitis.
  • Soft tissue masses — characterisation and sarcoma staging.
• Imaging isn't always needed — most soft tissue injuries and degenerative joint pain are clinical diagnoses.

Imaging in Major Trauma

• Primary survey first (<C>ABCDE) — control catastrophic haemorrhage; imaging must not delay life-saving treatment.
• Adjuncts to the primary survey:
  • Chest X-ray (supine) — haemothorax, pneumothorax, widened mediastinum, tube positions.
  • Pelvic X-ray — pelvic ring injury (if not going straight to CT).
  • eFAST — free fluid in the abdomen (hepatorenal, splenorenal, pelvis), pericardial fluid, pneumothorax — a positive FAST in an unstable patient supports going to laparotomy; a negative FAST doesn't exclude injury (retroperitoneal bleeding, hollow viscus).
• Whole-body CT (NICE NG39) — for adults with blunt major trauma and suspected multiple injuries — vertex to toes (or mid-thigh) — rapid, comprehensive; reported immediately (provisional "hot" report).
• Patients too unstable for CT — straight to theatre or interventional radiology (damage control); don't take unstable patients to CT unless the trauma team leader decides the benefit outweighs the risk.
• Children — targeted imaging (not routine whole-body CT) to reduce radiation; ultrasound and clinical assessment; CT head and c-spine by specific criteria.
• Key CT findings:
  • Active contrast extravasation ("blush") — ongoing bleeding — interventional radiology (embolisation of spleen, liver, kidney, pelvic arteries) or surgery.
  • Solid organ injury grading (spleen, liver, kidney) — many managed non-operatively.
  • Traumatic aortic injury, diaphragmatic rupture, bowel injury (free fluid without solid organ injury), pneumothorax, spinal fractures.
• Penetrating trauma — CT in stable patients; unstable patients go to theatre.
• Tertiary survey within 24 hours — re-examination for missed injuries (fingers, toes, ribs).
• Major trauma networks — major trauma centres with 24/7 CT and interventional radiology.

MSK and Trauma Imaging at a Glance

Problem	Imaging	Key point
Suspected scaphoid fracture	Scaphoid views → early MRI if negative	Proximal pole AVN; immobilise meanwhile
Suspected hip fracture	AP pelvis + lateral hip → MRI (CT if MRI unavailable within 24 hours)	Shenton's line; surgery day of or after admission
Elbow effusion	Lateral elbow X-ray	Posterior fat pad = occult fracture
Shoulder dislocation	AP + Y or axial view	Posterior — lightbulb sign; check axillary nerve
Ankle injury	Ottawa ankle rules	Weber C unstable; image whole fibula (Maisonneuve)
Knee injury	Ottawa knee rules; MRI for ligaments	Lipohaemarthrosis = intra-articular fracture; Segond = ACL
Suspected NAI	Skeletal survey (repeat at 11–14 days); CT head in infants	Metaphyseal corner and posterior rib fractures
Growth plate fracture	X-ray	Salter–Harris I–V (SALTR)
SUFE	AP + frog-leg lateral, both hips	Klein's line
Osteomyelitis	X-ray (late changes) → MRI	X-ray normal for 10–14 days
Bone sarcoma	X-ray within 48 hours (young people)	Aggressive periosteal reaction; refer to sarcoma centre
Myeloma	Whole-body low-dose CT or MRI	Bone scan often normal
Soft tissue lump growing	Urgent ultrasound	Over 5 cm, deep — sarcoma pathway
Major trauma	CXR, pelvis, eFAST → whole-body CT	Unstable — theatre or IR, not CT

Spot the Diagnosis

Clue	Diagnosis
Snuffbox tenderness after a fall; normal scaphoid views	Possible occult scaphoid fracture — immobilise and MRI
"Dinner fork" wrist in a 70-year-old woman	Colles' fracture — consider osteoporosis
Spilled teacup on the lateral wrist film with median nerve symptoms	Lunate dislocation
Raised posterior fat pad, no visible fracture, adult fall	Occult radial head fracture
Child with elbow pain; anterior humeral line misses the capitellum	Supracondylar fracture
Ulnar shaft fracture with radial head out of joint	Monteggia fracture-dislocation
Lightbulb humeral head after an epileptic seizure	Posterior shoulder dislocation
Disrupted Shenton's line; shortened externally rotated leg	Displaced intracapsular hip fracture
Can't weight-bear after a fall; hip X-rays normal	Occult hip or pubic ramus fracture — MRI
Fat–fluid level on a horizontal-beam lateral knee	Lipohaemarthrosis — intra-articular fracture
Small lateral tibial plateau avulsion after a twisting injury	Segond fracture — ACL tear
Medial ankle tenderness and proximal fibular pain	Maisonneuve fracture
Lateral malleolus fracture above the syndesmosis	Weber C — unstable
Horizontal L1 vertebral fracture after a car crash with abdominal pain	Chance fracture — look for bowel injury
Metaphyseal corner fractures and posterior rib fractures in a 4-month-old	Non-accidental injury
Obese 13-year-old boy with knee pain and limp	SUFE — X-ray both hips
Teenager with knee pain at night; sunburst periosteal reaction	Osteosarcoma
Night pain in the tibia relieved by ibuprofen; sclerosis around a lucent nidus	Osteoid osteoma
Lytic epiphyseal lesion reaching the joint surface in a 30-year-old	Giant cell tumour
Punched-out erosions with overhanging edges at the first MTP	Gout
Pencil-in-cup deformity of DIP joints with nail pitting	Psoriatic arthritis
Bilateral sacroiliitis and bamboo spine	Ankylosing spondylitis
Thickened cortex, enlarged bone and raised ALP in an 80-year-old	Paget's disease
Lucent bands in the pubic rami with low vitamin D	Looser's zones — osteomalacia
Hypotension, positive FAST in the splenorenal space after a crash	Splenic injury — laparotomy or embolisation

Exam-style Scenarios

1. An 85-year-old woman can't weight-bear after a fall. Hip X-rays (AP pelvis and lateral) show no fracture.
Answer: Suspected occult hip fracture.

• MRI hip (or CT if MRI is unavailable within 24 hours or contraindicated); look for pubic rami and acetabular fractures.
• Analgesia (including fascia iliaca block), orthogeriatric review, delirium and pressure care.
• If fracture confirmed — surgery on the day of or the day after admission; bone health assessment.

2. A 22-year-old man fell on his outstretched hand while snowboarding. He has snuffbox tenderness. Scaphoid series is normal.
Answer: Clinical scaphoid fracture.

• Immobilise (splint or cast) and arrange early MRI (or CT, or repeat X-rays at 10–14 days per local pathway).
• Explain the risk of avascular necrosis and non-union if a fracture is missed.
• Fracture clinic follow-up.

3. A 3-month-old has a swollen thigh. X-ray shows a spiral femoral fracture. The parents say he rolled off the sofa.
Answer: Possible non-accidental injury (fracture in a non-mobile infant).

• Follow local safeguarding procedures — senior paediatrician, social care referral.
• Skeletal survey (repeat at 11–14 days), CT head, ophthalmology for retinal haemorrhages; bloods (bone profile, vitamin D, clotting, FBC).
• Consider differentials (osteogenesis imperfecta, rickets); document carefully.

4. A 15-year-old boy has had pain above his right knee for 2 months, worse at night. X-ray shows a destructive distal femoral metaphyseal lesion with a sunburst periosteal reaction.
Answer: Suspected osteosarcoma.

• Very urgent referral (within 48 hours) to a specialist bone sarcoma service.
• Don't biopsy locally — biopsy is planned by the sarcoma surgeon.
• Staging (MRI of the whole bone, CT chest) at the sarcoma centre.

5. A 35-year-old motorcyclist is brought in after a high-speed crash. BP 80/50, HR 135. eFAST shows fluid in the hepatorenal pouch. Pelvic X-ray shows an open-book fracture.
Answer: Haemorrhagic shock from abdominal and pelvic bleeding.

• Pelvic binder, major haemorrhage protocol (blood products, tranexamic acid), permissive hypotension.
• Not stable for CT — damage control laparotomy and/or pelvic packing or interventional radiology embolisation, per trauma team leader.
• Whole-body CT once stabilised; tertiary survey within 24 hours.

Key Points

• Two views at right angles; include the joints above and below.
• Describe fractures — bone, site, pattern, displacement, angulation, joint involvement, open or closed, neurovascular status.
• Use Ottawa ankle and knee rules and the Canadian C-spine rule.
• Occult scaphoid and hip fractures — MRI.
• Elbow posterior fat pad = effusion = occult fracture; check the anterior humeral and radiocapitellar lines.
• Posterior shoulder dislocation — lightbulb sign; always get an axial or Y view.
• Weber C ankle fractures are unstable; image the whole fibula with medial ankle injuries.
• Salter–Harris I–V (SALTR); buckle fractures — splint, no follow-up X-ray.
• NAI — fractures in non-mobile infants, metaphyseal corner and posterior rib fractures; skeletal survey and CT head.
• SUFE — obese adolescent with knee pain; frog-leg views; Klein's line.
• OA — LOSS; RA — LESS; gout — punched-out erosions; psoriatic — pencil-in-cup; AS — sacroiliitis and bamboo spine.
• Aggressive bone lesions — wide zone of transition, Codman's triangle, sunburst, onion skin — sarcoma centre, no local biopsy.
• Myeloma — whole-body CT or MRI (bone scan cold); prostate metastases are sclerotic.
• Osteomyelitis — X-ray normal for 10–14 days; MRI is best.
• Major trauma — eFAST and adjuncts; whole-body CT for stable adults; unstable patients to theatre or IR.

Guidelines and Further Reading

• NICE NG38: Fractures (non-complex); NICE NG37: Fractures (complex)
• NICE CG124: Hip fracture — management; NICE NG39: Major trauma — assessment and initial management
• British Orthopaedic Association Standards for Trauma (BOAST) — open fractures, scaphoid, hip and others
• Royal College of Radiologists / Society and College of Radiographers: Imaging in suspected physical abuse (skeletal survey guidance)
• NICE NG12: Suspected cancer (bone and soft tissue sarcoma); NICE NG35: Myeloma
• NICE NG19: Diabetic foot problems; NICE NG226: Osteoarthritis
• Royal College of Radiologists: iRefer — musculoskeletal and trauma
• BNF — for current doses