Radiodiagnosis
Musculoskeletal Imaging
Musculoskeletal imaging for MBBS and NEET-PG: fracture radiographs, osteoarthritis and rheumatoid patterns, bone tumours, osteomyelitis and MRI for soft tissue, mapped to NMC code RD1.6.
MedNext Academy | 3 min read
Musculoskeletal Imaging
Musculoskeletal imaging for MBBS and NEET-PG: fracture radiographs, osteoarthritis and rheumatoid patterns, bone tumours, osteomyelitis and MRI for soft tissue, mapped to NMC code RD1.6.
This chapter covers the imaging of bones and joints, starting from the plain radiograph as the front-line test for trauma and arthritis. It teaches the radiographic patterns of fractures, osteoarthritis and rheumatoid arthritis, the signs of bone tumours and infection, and the growing role of MRI and ultrasound for soft tissue and occult injury.
High-yield: Musculoskeletal Imaging
- Radiographs remain the first-line investigation for suspected fracture, and at least two orthogonal views are needed to avoid missing an undisplaced fracture.
- Imaging of a suspected long-bone fracture should include the joint above and below the injury.
- A Colles fracture is a dorsally angulated and displaced fracture of the distal radius, giving the dinner-fork deformity, typically after a fall on an outstretched hand.
- A greenstick fracture is an incomplete fracture of the pliable paediatric bone, cortex broken on one side only.
- A pathological fracture occurs through abnormal bone weakened by tumour, infection or metabolic disease, sometimes after trivial trauma.
- Osteoarthritis shows joint space narrowing, subchondral sclerosis, osteophytes and subchondral cysts on the radiograph.
- Rheumatoid arthritis shows periarticular osteopenia, marginal erosions, uniform joint space loss and soft-tissue swelling, favouring the small joints.
- Acute osteomyelitis may be radiographically normal for the first one to two weeks, so MRI is the most sensitive early modality.
- A Codman triangle and a sunburst periosteal reaction suggest an aggressive bone tumour such as osteosarcoma, most common around the knee in adolescents.
- A lytic soap-bubble lesion at the epiphysis of a mature long bone suggests a giant cell tumour.
- MRI is the modality of choice for ligament, meniscus, cartilage and soft-tissue lesions and for occult and stress fractures.
- Ultrasound is useful for tendon injuries, joint effusions and guiding aspiration or injection in real time.
- Avascular necrosis of the femoral head shows early changes best on MRI, with the crescent sign of subchondral collapse appearing later on radiographs.
- A bone scan is highly sensitive for metastases, stress fractures and infection, though it is not specific.
Modality by problem
- **Fracture and arthritis:** Radiograph first line; two orthogonal views, joint above and below.
- **Ligament, meniscus, cartilage:** MRI is the modality of choice for internal joint derangement.
- **Early osteomyelitis and avascular necrosis:** MRI is most sensitive; radiographs lag by one to two weeks.
- **Tendons and effusions:** Ultrasound for real-time assessment and guided aspiration.
NMC competencies in this chapter
- **RD1.6:** Radiological investigation and interpretation in common surgical and orthopaedic conditions
Frequently Asked Questions
Why are two views needed for a suspected fracture?
A single view can hide an undisplaced or minimally angulated fracture. Two orthogonal views, usually at right angles, are needed, and the images should include the joint above and below the injury.
How do osteoarthritis and rheumatoid arthritis differ on radiographs?
Osteoarthritis shows non-uniform joint space narrowing, subchondral sclerosis and osteophytes. Rheumatoid arthritis shows uniform joint space loss, periarticular osteopenia and marginal erosions, favouring the small joints.
Why is MRI important in early osteomyelitis?
Plain radiographs may stay normal for the first one to two weeks of infection, while MRI detects the marrow oedema and soft-tissue changes early, making it the most sensitive investigation.
What imaging signs suggest an aggressive bone tumour?
A Codman triangle and a sunburst periosteal reaction indicate aggressive periosteal elevation, classically in osteosarcoma around the knee in adolescents, prompting MRI and biopsy.
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