Musculoskeletal

A chronic, symmetrical, deforming inflammatory polyarthritis driven by autoimmune synovitis, with extra-articular features. Early diagnosis and early DMARD therapy (treat-to-target) prevent joint destruction. Anti-CCP is the most specific antibody; the small joints of the hands and feet are affected first, with morning stiffness lasting over an hour.

A chronic seronegative spondyloarthropathy causing inflammatory axial pain and progressive fusion of the spine and sacroiliac joints. Typically a young man with inflammatory back pain (worse with rest, better with exercise, prolonged morning stiffness) and HLA-B27 positivity. The extra-articular 'A's (anterior uveitis, aortic regurgitation, apical lung fibrosis) are high-yield.

An inflammatory arthritis associated with psoriasis (which may precede, accompany or follow the joint disease). It has several patterns — including a DIP-predominant form, asymmetrical oligoarthritis, a symmetrical RA-like polyarthritis, spondylitis, and the destructive arthritis mutilans. Dactylitis, enthesitis and nail changes are clues.

Reactive arthritis is a sterile, HLA-B27-associated inflammatory arthritis arising days to weeks after a urogenital (Chlamydia) or gastrointestinal (Salmonella, Shigella, Campylobacter, Yersinia) infection — the classic triad 'can't see, can't pee, can't climb a tree' (conjunctivitis, urethritis, arthritis). Enteropathic arthritis is the spondyloarthropathy associated with inflammatory bowel disease.

Arthritis beginning before age 16 and lasting more than 6 weeks, with several subtypes (oligoarticular — the commonest, polyarticular, systemic/Still's disease, enthesitis-related, psoriatic). Systemic JIA (Still's) presents with quotidian fever, a salmon-pink rash and arthritis. The major sight-threatening complication is chronic anterior uveitis, which is often asymptomatic and needs screening. Detailed paediatric management is on the child_health page.

The commonest joint disease: progressive loss of articular cartilage with subchondral bone change, osteophytes and low-grade inflammation. It is a clinical diagnosis in those over 45 with activity-related joint pain and no prolonged morning stiffness. Management is core (exercise, weight loss, education) plus analgesia, with joint replacement for end-stage disease.

Deposition of monosodium urate crystals from sustained hyperuricaemia, causing acute attacks of agonising monoarthritis (classically the first MTP joint — podagra), tophi and chronic arthropathy. Aspiration shows negatively birefringent needle-shaped crystals. Acute attacks are treated with anti-inflammatories; urate-lowering therapy prevents recurrence.

Acute or chronic arthritis from calcium pyrophosphate dihydrate (CPPD) crystal deposition, typically in larger joints (knee, wrist) of older people. Aspiration shows positively birefringent rhomboid crystals; X-ray shows chondrocalcinosis (cartilage calcification). It can be precipitated by intercurrent illness and is associated with metabolic conditions (haemochromatosis, hyperparathyroidism).

A multisystem autoimmune disease, predominantly in women of reproductive age (and more common/severe in those of African/Asian ancestry), characterised by autoantibodies, immune-complex deposition and a relapsing-remitting course. ANA is the sensitive screen; anti-dsDNA and anti-Smith are specific. It is a great mimic — joints, skin, kidneys, blood, serosa, CNS — and lupus nephritis drives prognosis.

An autoimmune connective tissue disease causing skin and internal-organ fibrosis with a small-vessel vasculopathy. Limited cutaneous SS (formerly CREST — Calcinosis, Raynaud's, oEsophageal dysmotility, Sclerodactyly, Telangiectasia; anti-centromere) has a more indolent course but risks pulmonary hypertension; diffuse cutaneous SS (anti-Scl-70/topoisomerase) carries the risk of interstitial lung disease and scleroderma renal crisis. Raynaud's is almost universal.

An autoimmune disease in which lymphocytic infiltration destroys exocrine (especially lacrimal and salivary) glands, causing dry eyes and dry mouth (sicca). It may be primary or secondary to another connective tissue disease (RA, SLE). Anti-Ro (SSA) and anti-La (SSB) antibodies are characteristic; the major long-term risk is a markedly increased incidence of B-cell (MALT) lymphoma.

Idiopathic inflammatory myopathies causing symmetrical proximal muscle weakness from immune-mediated muscle inflammation. Dermatomyositis adds characteristic skin signs (heliotrope rash, Gottron's papules). Both — dermatomyositis especially — carry a paraneoplastic association, so an age-appropriate malignancy screen is essential. Creatine kinase is markedly raised.

A large-vessel granulomatous vasculitis of those over 50, affecting the cranial branches of the carotid (and the aorta). It is a medical emergency because of the risk of irreversible visual loss from anterior ischaemic optic neuropathy. It strongly overlaps with polymyalgia rheumatica. High-dose steroids must be started immediately on clinical suspicion — before the biopsy.

An inflammatory condition of people over 50 causing bilateral pain and prolonged morning stiffness of the shoulder and pelvic girdles, with raised inflammatory markers and a dramatic response to low-dose steroids. There is NO true muscle weakness (stiffness limits movement). It overlaps with giant cell arteritis, so cranial symptoms must be sought.

A heterogeneous group of conditions defined by blood-vessel-wall inflammation, classified by vessel size: large (GCA, Takayasu), medium (polyarteritis nodosa, Kawasaki) and small (ANCA-associated — GPA, EGPA, MPA — and immune-complex, e.g. IgA vasculitis/HSP). They present with multisystem disease and constitutional symptoms; ANCA-associated vasculitis classically causes a pulmonary-renal syndrome. Many are organ- and life-threatening and need immunosuppression.

A chronic widespread pain syndrome driven by central sensitisation/abnormal pain processing, without inflammation or structural damage. It presents with diffuse pain, profound fatigue, unrefreshing sleep and cognitive 'fog', with normal investigations. It is a positive clinical diagnosis (not one of exclusion alone), and management is non-pharmacological first — exercise, education and psychological therapy.

Low back pain is usually non-specific and self-limiting; sciatica is radicular leg pain from lumbosacral nerve-root compression (often a disc prolapse). The key skill is triage: recognise the red flags for a serious cause (cauda equina, malignancy, infection, fracture) while managing the large majority conservatively with the STarT Back risk-stratified approach.

Compression of the cauda equina nerve roots below the conus medullaris — most often by a large central lumbar disc prolapse, but also tumour, abscess or haematoma. It is a surgical EMERGENCY: delayed decompression risks permanent bladder, bowel and sexual dysfunction and leg weakness. Any back pain with bladder/bowel or saddle symptoms mandates immediate MRI.

Herniation of the disc's nucleus pulposus through the annulus fibrosus, compressing an adjacent nerve root and causing radicular pain (sciatica in the lumbar spine, brachialgia in the cervical spine). Most resolve with conservative management; the surgical concern is a large central prolapse causing cauda equina syndrome.

A skeletal disorder of low bone mass and disrupted microarchitecture that increases fracture risk. It is silent until a fragility fracture (a fracture from a fall from standing height or less) — classically wrist, hip and vertebrae. Risk is assessed with FRAX/QFracture and DEXA; bisphosphonates are first-line treatment. It is the major reason to treat after any fragility fracture.

Defective mineralisation of bone matrix, usually from vitamin D deficiency (also renal disease, hypophosphataemia). In adults it is osteomalacia (bone pain, proximal weakness, fractures); in children with open growth plates it is rickets (bowed legs, swollen joints, growth failure). The biochemistry — low/normal calcium and phosphate with HIGH ALP — distinguishes it from osteoporosis (normal biochemistry).

Bacterial infection within a joint space — an orthopaedic EMERGENCY because pus rapidly destroys articular cartilage. Staphylococcus aureus is the commonest organism; Neisseria gonorrhoeae is important in young sexually active adults. Any acutely hot, swollen, painful joint must be aspirated and treated as septic until proven otherwise.

Infection of bone, by haematogenous spread (children — long-bone metaphysis; adults — vertebrae) or contiguous spread (diabetic foot, trauma, prosthesis). Staphylococcus aureus is the commonest organism; Salmonella is classic in sickle cell disease. MRI is the most sensitive imaging; treatment is prolonged antibiotics ± surgical debridement.

Bone malignancy is far more often secondary (metastases from breast, prostate, lung, kidney, thyroid; and myeloma) than primary. Primary bone sarcomas — osteosarcoma (adolescents, around the knee), Ewing sarcoma (children/young, diaphysis), chondrosarcoma (older) — are rare but important. Persistent bone pain (especially night pain), a pathological fracture or a destructive lesion should prompt urgent investigation.

A breach of bone continuity. Most follow trauma; a fragility fracture follows low-energy trauma (osteoporosis); a pathological fracture occurs through abnormal bone (metastasis, myeloma, primary tumour, Paget's) with minimal or no trauma. Management follows reduce–hold–rehabilitate, with attention to the soft tissues and the underlying bone health or pathology.

Fractures cause important complications that are heavily examined. Immediate/early: neurovascular injury, compartment syndrome, fat embolism, infection, VTE. Late: non-union, malunion, avascular necrosis (sites with precarious blood supply — femoral head, scaphoid, talus), and post-traumatic osteoarthritis. Compartment syndrome is the can't-miss emergency.

Loss of the normal articulation of a joint — complete (dislocation) or partial (subluxation). The shoulder is the commonest (usually anterior); other key ones are the patella, hip (including prosthetic), and the elbow. The priorities are prompt reduction, documenting neurovascular status before and after, and post-reduction imaging.

Injury or inflammation of the periarticular soft tissues — ligament sprains, muscle/tendon strains, tendinopathy, bursitis and enthesopathy. They are common, usually managed conservatively (relative rest, analgesia, physiotherapy), and the main skill is recognising the few that need more — an Achilles tendon rupture, a septic bursitis, or an underlying inflammatory cause.

A chronic relapsing multisystem inflammatory disorder classed as a variable-vessel vasculitis (it can affect vessels of any size, arterial and venous). It is most common in young adults from the eastern Mediterranean and Silk Road regions and is associated with HLA-B51. The hallmark is recurrent painful oral AND genital ulceration, with anterior uveitis, skin lesions, and a positive pathergy test.

Degenerative narrowing of the lumbar spinal canal (from facet/ligamentum flavum hypertrophy, disc bulging and osteophytes) compressing the nerve roots. It causes neurogenic claudication in older adults — and its discrimination from vascular claudication and from a simple disc prolapse is the high-yield skill. The give-away is that flexion (sitting, leaning on a trolley, walking uphill) relieves it.

Frailty is a state of reduced reserve in which a minor stressor — a urinary tract infection, a new drug, an unfamiliar ward — produces a disproportionate and often sustained decline in function. Sarcopenia is the loss of skeletal muscle mass, strength and function that underpins much of it. Frailty is a diagnosis to be made explicitly, not a synonym for being old.