Introduction
Musculoskeletal (MSK) plain films are a daily reality in radiology, yet distinguishing between a benign lesion, an aggressive tumor, or an early infection can be daunting. As a busy postgraduate, you need a quick, reliable system—a 2-Minute Guide—that ensures you don’t miss key findings.
This guide provides the Ultimate MSK X-Ray Interpretation Checklist focused specifically on non-trauma cases (tumors, arthritis, and infection). Use this checklist to structure your reports and impress your attendings.
The ABCs-TM System: Your 2-Minute MSK Checklist
Adopt this systematic approach to analyze every non-trauma X-ray and structure your thought process.
| Step | Area of Focus | Key Questions to Ask |
| A | Alignment & Architecture | Is the joint space preserved or lost? Are there any subluxations? Are bone contours normal? |
| B | Bone Density & Texture | Is the bone density normal (osteopenia/sclerosis)? Is the cortex intact? Is there periosteal reaction? |
| C | Cartilage & Calcification | Is there joint space narrowing (suggesting arthritis)? Are there calcifications in soft tissues or cartilage? |
| S | Soft Tissues | Is there swelling, effusions, or masses adjacent to the bone? (Especially important for occult infection). |
| T | Tumor Matrix | What is the lesion producing? (O/C/F) Is it Ossified (e.g., Osteosarcoma), Chondroid (e.g., Chondrosarcoma), or Fibrous? |
| M | Margins & Marrow | Is the lesion margin geographic (benign), moth-eaten (aggressive), or permeative (highly aggressive)? Is there internal marrow change? |
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Focus Area 1: Bone Lesions (The T&M of the System)
The key to interpreting a bone lesion is assessing its aggressiveness based on the pattern of bone destruction and the host response.
Aggressiveness Spectrum:
- Geographic Destruction (Least Aggressive): Sharp, well-defined margins (e.g., Non-ossifying fibroma, simple bone cyst).
- Moth-Eaten Destruction (Aggressive): Multiple small holes coalescing. Indicates rapid growth (e.g., Metastasis, Myeloma).
- Permeative Destruction (Most Aggressive): Ill-defined, tiny holes. Indicates highly rapid infiltration (e.g., Ewing sarcoma, infection).
Periosteal Reaction (Host Response):
- Benign/Slow-Growing: Solid, thick, or undulating.
- Aggressive/Rapidly Growing: Sunburst, Codman triangle (triangular new bone under lifted periosteum), or laminated/onion-skin (concentric layers).
Focus Area 2: Arthritis (The A&C of the System)
When dealing with arthritic changes, categorize the disease pattern immediately.
| Arthritis Type | Hallmark X-Ray Findings |
| Osteoarthritis (OA) | Asymmetric joint space loss, Osteophytes, Subchondral sclerosis, Subchondral cysts. |
| Rheumatoid Arthritis (RA) | Symmetric joint space loss, Marginal Erosions, Periarticular osteopenia. |
| Gout | Eccentric, juxta-articular erosions with overhanging edges (rat-bite). Joint space is often preserved initially. |
| Psoriatic Arthritis (PsA) | “Pencil-in-cup” deformity (resorption of the terminal phalanx), periostitis. |
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Conclusion
The MSK X-ray isn’t a guessing game; it’s a systematic analysis. By utilizing the ABCs-TM checklist, you establish a framework that handles the most common and the most dangerous non-traumatic pathology efficiently.
Don’t wait until call night to memorize this.
