Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Paget disease of bone
Musculoskeletal medicine and orthopaedics · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Time-critical presentation
A sudden painful deformity or inability to bear weight in an affected limb is a pathological fracture until proved otherwise: immobilise, document distal neurovascular function and obtain urgent orthopaedic imaging. New weakness, sensory change or bladder or bowel dysfunction with spinal Paget disease requires emergency MRI and spinal review. Rapidly escalating focal pain, enlarging mass or aggressive bone destruction raises sarcomatous transformation and must enter a specialist bone-tumour pathway before biopsy.
Overview
Distinguish active pagetic bone pain from mechanical joint and fracture complications, map affected sites and coordinate antiresorptive treatment with safe deformity, fixation and arthroplasty planning.
Clarify how the disease was found and whether current pain is bony, articular or neurological. Active bone pain is often deep, persistent and present at rest, with local warmth. Osteoarthritic pain relates more to movement and joint-line loading, while focal pain in a bowed femur or tibia may mark a fissure fracture. Ask about increasing hat size, hearing, dental fit, limb bowing, previous fracture, gait change and family history. Rapid progression or mass is a tumour warning.
Inspect skull contour, limb alignment and gait and compare local temperature. Palpate the full painful bone and adjacent joints, measure range and assess leg length and mechanical axis. Complete a neurological examination for spinal or skull-base disease and document pulses and nerve function before managing a deformed limb. Do not attribute every symptom to Paget disease: examine hip, knee, lumbar spine and vascular status for common competing causes.
Aetiology
01
Genetic susceptibility
Variants affecting osteoclast signalling, particularly SQSTM1 in some families, increase susceptibility but do not fully determine anatomical distribution or severity.
02
Age-related expression
Disease is uncommon before midlife and becomes more prevalent with age, reflecting delayed focal emergence of abnormal remodelling in predisposed bone.
03
Geographical and familial pattern
Prevalence is higher in parts of the United Kingdom and among relatives of affected people, although incidence has declined across recent generations.
04
Uncertain environmental triggers
Proposed viral and environmental factors remain unproven; clinical decisions rely on skeletal activity and complications rather than a presumed external cause.
Pathophysiology
1
Accelerated resorption
Large abnormal osteoclasts remove focal bone rapidly, initiating a turnover cycle that is far more active than surrounding normal skeleton.
2
Disorganised replacement
Osteoblasts refill resorption spaces quickly with woven and lamellar bone arranged in a mosaic pattern rather than normal load-oriented architecture.
3
Expansion and hypervascularity
High turnover enlarges cortex and increases local blood flow, producing warmth, skull enlargement and greater operative blood loss despite apparently dense radiographs.
4
Mechanical weakness
Pagetic bone is enlarged yet structurally inefficient, allowing bowing, fissure fracture and complete transverse failure under repeated weight-bearing load.
5
Secondary joint overload
Femoral or tibial deformity changes joint axes and concentrates cartilage stress, causing osteoarthritis that does not necessarily improve when biochemical activity is suppressed.
Clinical features and red flags
Expanded coarse bone
Cortical thickening, trabecular coarsening and enlargement on radiography form the characteristic anatomical pattern when interpreted by site.
Bone-source ALP rise
Raised total ALP with non-cholestatic liver tests supports active skeletal turnover, though limited disease can have a normal result.
Pagetic bone pain
Deep persistent ache with focal warmth differs from pain confined to joint movement or a tender lateral cortical fissure.
Bowing and stress pain
Progressive femoral or tibial curvature with new load pain localises tension to the convex cortex and warns of incomplete fracture.
Secondary joint disease
Restricted hip or knee motion, joint-line tenderness and radiographic cartilage loss explain mechanical disability beyond biochemical activity.
Sarcoma warning change
A rapidly enlarging mass, new relentless focal pain and destructive cortex is malignant transformation until a tumour service determines otherwise.
Red flags requiring action
A new fracture through expanded femur or tibia can bleed, displace and be technically difficult to stabilise; protect the limb and refer urgently.
New neurological deficit, gait deterioration or sphincter change with vertebral enlargement suggests canal compromise requiring emergency spinal assessment.
Investigations
01First-line targeted plain radiographsFirst stepFirst line
Why
Confirm characteristic architecture, identify deformity and fracture and screen for an aggressive alternative.
Interpretation and limitations
Expansion with cortical and trabecular thickening supports Paget disease; permeative loss or a mass needs urgent tumour referral.
02Total ALP with liver profile
Why
Estimate skeletal turnover and separate bone-source elevation from cholestatic liver disease.
Interpretation and limitations
Marked isolated ALP elevation supports active burden, but normal total ALP cannot exclude monostotic disease.
03Radionuclide bone scintigraphy
Why
Map all metabolically active skeletal sites after radiographic diagnosis.
Interpretation and limitations
This is the reference extent study, not a stand-alone diagnostic biopsy substitute; correlate atypical or solitary uptake anatomically.
04MRI or CT for a complication
Why
Define occult fissure, canal or nerve compression, sarcoma extent, deformity and operative anatomy.
Interpretation and limitations
MRI favours marrow, neural and soft tissue; CT best displays cortex, sclerosis and three-dimensional bony geometry.
05
Differential diagnosis
01
Skeletal metastasis
Multifocal sclerosis or lysis without characteristic expansion, especially with cancer symptoms, needs cross-sectional imaging and oncological correlation.
02
Fibrous dysplasia
Ground-glass matrix and deformity arising earlier in life can mimic pagetic expansion but has a different distribution and natural history.
03
Chronic osteomyelitis
Sinus, sequestrum, systemic inflammation or previous surgery suggests infection; warmth and remodelling alone should not prompt empiric antibiotics.
04
Osteoarthritis
Activity-related joint-line pain, restricted motion and cartilage loss may explain symptoms better than active bone turnover adjacent to the joint.
05
Primary bone sarcoma
Aggressive periosteal reaction, permeative destruction, mass or escalating rest pain requires tumour-centre staging and planned biopsy regardless of known Paget disease.
Management
01DiagnosticConfirm and map focal diseaseFirst stepCharacteristic symptoms, incidental imaging or isolated bone-source ALP raises suspicion.+
1Obtain targeted radiographs and total ALP with liver, calcium, phosphate, renal and vitamin-D tests.
2Confirm typical anatomy before ordering a radionuclide scan to map active skeletal distribution.
3Correlate additional uptake with radiographs or cross-sectional imaging rather than labelling every focus pagetic.
4Refer atypical destruction or mass directly to a bone-tumour service before any local biopsy.
02FractureProtect bowed painful boneNew focal weight-bearing pain, fissure or complete fracture affects a pagetic long bone.+
1Stop unprotected loading, immobilise as appropriate and document skin and distal neurovascular findings.
2
Complications
01
Bowing and fissure fracture
Anterolateral femoral or tibial curvature concentrates tensile stress, producing painful incomplete lateral cortical cracks that may progress to complete fracture.
02
Secondary osteoarthritis
Pelvic, femoral and tibial deformity alters hip or knee loading and can cause disabling cartilage disease despite controlled pagetic turnover.
03
Neural compression
Vertebral expansion, stenosis or skull-base change can compress cord, roots or cranial nerves and occasionally threaten hearing or brainstem function.
04
Operative complexity
Sclerotic deformed hypervascular bone complicates exposure, reaming, implant alignment and fixation while increasing blood loss, non-union and implant-failure risk.
05
Sarcomatous transformation
Rare osteosarcoma or other sarcoma presents with new severe focal pain, swelling, destructive imaging and poor prognosis, demanding urgent specialist referral.
Monitoring and follow-up
Record baseline pain location and whether it is bony, joint-related, neurological or fracture-like before treatment.
Recheck ALP or the selected turnover marker after bisphosphonate according to the specialist plan and relate change to symptoms.
Repeat renal and calcium assessment when clinically indicated after potent intravenous treatment, especially in frailty or kidney disease.
Re-image immediately for altered focal pain, new mass or loss of weight-bearing rather than waiting for scheduled biochemical follow-up.
Monitor alignment, leg length, gait, joint range and hearing when affected anatomical sites can cause progressive mechanical disability.
After reconstruction, follow union, implant alignment, blood loss consequences and loading tolerance more closely than ALP alone.
Special situations
Dense does not mean strong
Pagetic radiographs can look sclerotic while disorganised architecture remains deformable and vulnerable to fracture and implant failure.
Pain needs anatomical attribution
Active turnover, osteoarthritis, a cortical fissure and sarcoma can occur in the same bone yet require entirely different care.
Scintigraphy maps rather than proves
High uptake is sensitive for activity but needs radiographic correlation because metastasis, fracture and arthritis can also accumulate tracer.
Normal ALP can coexist
A small monostotic focus may produce too little total skeletal turnover to elevate the routine serum marker.
Biochemistry cannot straighten bone
Zoledronate suppresses active remodelling but does not reverse established bowing, joint destruction or canal narrowing.
The whole bone matters
A narrow radiograph may miss a remote fissure, curvature or joint deformity that determines safe implant selection.
Common pitfalls
01
Treating a raised ALP without proving skeletal origin, radiographic disease or a relevant clinical target.
02
Assuming persistent hip or knee pain reflects active Paget disease when secondary osteoarthritis is the main generator.
03
Allowing full weight bearing through new focal pain in a bowed femur or tibia before excluding a fissure.
04
Planning standard intramedullary fixation without imaging the full curved canal and adjacent joints.
05
Biopsying a new destructive lesion locally instead of referring before the biopsy tract is chosen by the sarcoma team.
06
Repeating zoledronic acid automatically each year despite prolonged biochemical remission and no pagetic bone pain.
Practice
Two practice questions
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Question 1 of 2
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Musculoskeletal medicine and orthopaedicsOriginal SBA
New focal pain in bowed bone
A patient with known tibial Paget disease develops new focal pain over the convex cortex when weight bearing. There is no systemic illness. What is the safest immediate approach?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Radiographs show cortical thickening, coarsened trabeculae, bone expansion and region-specific patterns such as pelvic brim thickening or blade-of-grass advancing osteolysis. Image the entire symptomatic long bone, including both joints, because deformity and fissures can extend beyond a narrow field. A new aggressive lytic area, interrupted cortex, periosteal reaction or soft-tissue mass is not routine activity and enters the sarcoma pathway.
Check total ALP with liver tests to establish whether elevation is likely skeletal. Calcium and phosphate are usually normal outside immobilisation or other disease. When total ALP is normal but radiographic monostotic disease appears active, bone-specific ALP, PINP or resorption markers can support assessment. Radionuclide scintigraphy then maps metabolically active distribution; it is sensitive but not specific, so unexpected uptake requires targeted anatomical imaging.
Treat the explanation for disability. A painful incomplete fissure needs load protection and orthopaedic assessment, not analgesia alone. Secondary hip or knee arthritis is managed with activity adaptation, aids, analgesia and selected arthroplasty. Neural compression needs MRI and spinal or skull-base review. Bisphosphonate may relieve active pagetic bone pain, but it does not straighten established deformity, repair advanced cartilage loss or decompress a stenotic canal.
For active disease causing bone pain, intravenous zoledronic acid 5 mg once is preferred when renal function, calcium and vitamin-D status permit. Verify adequate mineral intake and hydration and explain transient fever, myalgia and arthralgia after the first infusion. Oral risedronate can be used where infusion is unsuitable under specialist guidance. Calcitonin is rarely used when bisphosphonates cannot be given. Re-treatment follows clinical relapse rather than automatic annual dosing.
Pagetic fracture fixation must account for curvature and dense but weak bone. A standard straight intramedullary implant may not pass through a bowed canal, while plates face long lever arms and poor biology. Preoperative CT can define anatomy, and corrective osteotomy may be combined with fixation in selected cases. Arthroplasty planning addresses acetabular or femoral deformity, sclerotic reaming, blood loss and component position. Control of active turnover before elective surgery may be considered, but evidence for reducing blood loss is limited.
Follow pain and function alongside ALP or a chosen marker. A large biochemical fall after zoledronate confirms suppression, but persistent joint pain can remain entirely mechanical. Re-image a focal site when pain changes rather than assuming biochemical relapse. Hearing loss needs audiology, and neurological symptoms require urgent imaging. Relatives do not undergo indiscriminate scanning; specialist advice can guide ALP screening in families with strong or genetically confirmed disease.
Key points
Paget disease is focal accelerated remodelling that produces expanded, hypervascular and mechanically disorganised bone, commonly affecting pelvis, spine, femur, tibia and skull.
First-line confirmation uses radiographs of suspected sites plus total ALP with liver tests; normal ALP does not exclude limited monostotic disease.
After characteristic radiographic diagnosis, radionuclide bone scintigraphy is the reference test for mapping active skeletal extent, with radiographic correlation of unexpected uptake.
Decide what causes pain: active bone, an incomplete fissure fracture, secondary osteoarthritis, spinal stenosis, nerve compression or sarcoma require different interventions.
Bisphosphonate treatment is first-line for pain attributable to active Paget disease; a single 5 mg intravenous zoledronic-acid infusion gives the most durable biochemical response when safe.
Do not treat an isolated ALP result or chase biochemical normality in every asymptomatic patient; target symptoms and defined complication risk.
Protect weight bearing and image the whole bowed femur or tibia when new focal lateral-cortex pain suggests an incomplete pagetic fracture.
Plan osteotomy, fixation or arthroplasty with an experienced team because deformity, sclerosis, altered anatomy and hypervascularity change implant choice and blood-loss preparation.
Rapidly increasing focal pain, soft-tissue mass, cortical destruction or a new lytic focus may represent osteosarcoma arising in pagetic bone.
Headache with abrupt hearing, cranial-nerve or basilar-invagination symptoms needs targeted skull-base and neurological assessment rather than routine ALP monitoring.
Warmth and raised ALP with fever or markedly raised inflammatory markers can reflect infection, malignancy or another process rather than uncomplicated activity.
Hypercalcaemia during prolonged immobilisation or dehydration requires urgent biochemical assessment and treatment of the precipitating condition.
Bone-specific turnover marker
Why
Assess activity when liver disease confounds ALP or limited disease yields a normal total value.
Interpretation and limitations
Use bone-specific ALP or PINP consistently for follow-up; no marker distinguishes sarcoma from benign activity.
Image the full bone and adjacent joints, using CT when deformity or cortical detail affects planning.
3Obtain experienced orthopaedic input for prophylactic or fracture fixation that accounts for canal curvature and weak hypervascular bone.
4Treat active metabolic disease and plan blood, VTE and rehabilitation requirements alongside surgery.
03Symptom treatmentTarget active bone painClinical and imaging correlation attributes pain to active pagetic remodelling.+
Give a single 5 mg intravenous infusion over at least 15 minutes after confirming suitable creatinine clearance, hydration, corrected calcium and adequate vitamin-D and calcium intake.
Avoid in severe renal impairment or hypocalcaemia; warn about acute fever and myalgia and review dental risk, atypical femoral symptoms and rare ocular inflammation.
Suppresses active pagetic turnover when a supervised oral course is more appropriate.
Risedronate alternative oral bisphosphonate
Where intravenous treatment is unsuitable, a specialist may use risedronate 30 mg orally once daily for two months, taken fasting with plain water while upright according to the product instructions.
Check oesophageal disease, ability to follow administration, renal function, calcium and vitamin D; adherence and gastrointestinal intolerance can limit effectiveness.
Supports mobility when osteoarthritis or deformity contributes pain while definitive mechanical assessment proceeds.
Paracetamol for mechanical pain
Take 500 to 1,000 mg orally when required, keep every dose at least four hours apart and limit the 24-hour total to 4 g; lower that ceiling for low weight, frailty, malnutrition or liver risk.
Check combination products and alcohol or hepatic disease; symptom relief must not justify loading through a suspected fissure fracture.