Master CPS - Musculoskeletal
for MSRA

What the MSRA Tests in CPS - Musculoskeletal

The MSRA CPS Musculoskeletal domain tests clinical decision-making in primary care and emergency settings. Candidates must manage acute presentations like fractures, dislocations, septic arthritis, and gout, as well as chronic conditions such as osteoarthritis, rheumatoid arthritis, and osteoporosis. Key decisions include when to aspirate a joint, when to refer for suspected cauda equina syndrome, and appropriate first-line analgesia or disease-modifying drugs. Knowledge of NICE guidelines for fracture risk assessment (FRAX), DEXA scan thresholds, and DMARD monitoring is essential. The exam emphasises safe triage, red flag recognition, and cost-effective prescribing, with a focus on UK primary care pathways and referral criteria.

High-Yield Concepts

• Septic Arthritis vs Gout/Pseudogout: Septic arthritis is an emergency: aspirate joint before antibiotics. Gram stain and culture, plus serum CRP >100 mg/L and WCC >50,000/μL in joint fluid suggest infection. Gout: monosodium urate crystals, negative birefringence. Pseudogout: calcium pyrophosphate crystals, positive birefringence. First-line for acute gout: NSAIDs (naproxen) or colchicine if contraindicated.
• Osteoarthritis Management: NICE recommends non-pharmacological: exercise, weight loss, joint bracing. First-line analgesia: topical NSAIDs (e.g., diclofenac gel) for knee/hand; oral NSAIDs with PPI cover if insufficient. Avoid paracetamol as monotherapy. Intra-articular corticosteroids for flare. Refer for joint replacement if severe symptoms affecting quality of life.
• Rheumatoid Arthritis Diagnosis and DMARDs: Diagnosis: clinical (symmetrical small joint swelling, morning stiffness >30 min) plus serology (RF, anti-CCP). NICE: urgent referral if persistent synovitis. First-line DMARD: methotrexate (start 7.5-15 mg once weekly, with folic acid). Monitor FBC, LFTs, creatinine monthly for 3 months. Add sulfasalazine or leflunomide if inadequate response.
• Osteoporosis: FRAX and Treatment Threshold: NICE: offer DEXA if FRAX 10-year probability of major fracture ≥10% (or QFracture ≥10%). Treatment: alendronate 70 mg weekly (first-line), with calcium/vitamin D. If intolerant: risedronate, zoledronic acid, or denosumab. Reassess after 5 years. For hip fracture: start bisphosphonate immediately post-op.
• Cauda Equina Syndrome Red Flags: Red flags: bilateral sciatica, saddle anaesthesia, urinary retention/incontinence, faecal incontinence, progressive motor weakness. Suspect: MRI spine within 24 hours. Do not perform lumbar puncture. Immediate neurosurgical referral. Signs: loss of anal tone, perianal sensation, and bulbocavernosus reflex.
• Fracture Healing and Complications: Union expected at 6-8 weeks (upper limb) to 12-16 weeks (lower limb). Non-union: no healing at 9 months. Risk factors: smoking, diabetes, NSAIDs. Compartment syndrome: pain out of proportion, paraesthesia, pallor, pulselessness (late). Emergency fasciotomy if intracompartmental pressure >30 mmHg or diastolic BP minus compartment pressure <30 mmHg.
• Giant Cell Arteritis Diagnosis and Treatment: Suspect in >50 years with new headache, scalp tenderness, jaw claudication, elevated ESR/CRP. Urgent temporal artery biopsy within 7 days. Start high-dose prednisolone 40-60 mg daily immediately (do not wait for biopsy). If visual symptoms: IV methylprednisolone. Monitor for aortic aneurysm.
• Ankylosing Spondylitis and Biologics: Diagnosis: inflammatory back pain (morning stiffness >30 min, improves with exercise, not rest), sacroiliitis on MRI, HLA-B27 positive. First-line: NSAIDs (naproxen) and physiotherapy. If inadequate: TNF inhibitor (adalimumab, etanercept) after failure of two NSAIDs. Screen for TB and hepatitis B before starting biologic.

Common Traps in CPS - Musculoskeletal Questions

• Do not give antibiotics before aspirating a hot swollen joint; it reduces culture yield and delays diagnosis of septic arthritis.
• Do not use paracetamol as first-line for osteoarthritis; NICE recommends topical NSAIDs or oral NSAIDs with PPI.
• Do not start bisphosphonates in premenopausal women without specialist advice; teratogenic risk and alternative causes of low BMD must be excluded.
• Do not delay steroids in suspected giant cell arteritis while awaiting biopsy; start prednisolone immediately to prevent blindness.
• Do not perform lumbar puncture in suspected cauda equina syndrome; it risks coning and delays MRI.
• Do not forget to check FBC, U&E, LFTs before and during methotrexate therapy; missing monitoring can lead to fatal myelosuppression.

How to Revise CPS - Musculoskeletal for the MSRA

Prioritise acute joint presentations (septic vs crystal) and red flag recognition for back pain and fractures. Questions often present a clinical scenario with multiple labs and imaging results; practise interpreting synovial fluid analysis, DEXA T-scores, and inflammatory markers. Focus on NICE guidelines for osteoporosis and rheumatoid arthritis, especially treatment escalation rules. Expect questions on safe prescribing (NSAID contraindications, DMARD monitoring) and when to refer urgently. Review the NICE clinical knowledge summaries for gout, OA, and back pain. Practise timed decision-making: choose the next best step, not the definitive diagnosis.

Practise it: MedLumen has 50 CPS - Musculoskeletal questions for the MSRA, each with a full explanation and references.