Populations and Risk Factors
- DMD and BMD: X-linked recessive inheritance — primarily affects males; mothers are carriers (typically asymptomatic); females are affected only in rare circumstances (homozygous mutation, skewed X-inactivation, or Turner syndrome)
- DMD onset between ages 2–5; wheelchair-dependent by age 10–12; life expectancy into the late 20s–30s with modern cardiac and respiratory management
- BMD onset typically between ages 5–15; milder course; ambulation preserved into the 20s–30s or later; life expectancy into the 40s–50s or beyond
- Other types have different inheritance patterns:
- Facioscapulohumeral MD (FSHD): autosomal dominant; affects both sexes; onset in teens; relatively mild; facial and shoulder girdle weakness
- Myotonic dystrophy (DM): autosomal dominant; most common adult-onset form; affects both sexes; myotonia (delayed muscle relaxation) is the distinguishing feature
- Limb-girdle MD (LGMD): autosomal dominant or recessive; hip and shoulder girdle weakness
- Oculopharyngeal MD: autosomal dominant; late onset (40s–50s); ptosis and dysphagia
- Family history is the primary risk factor — one-third of DMD cases arise from spontaneous new mutations with no family history
- Serum creatine kinase (CK) is massively elevated in DMD (10–100 times normal) and is the primary screening marker
Causes and Pathophysiology
The Dystrophin Defect
- Dystrophin is a large structural protein that anchors the internal cytoskeleton of muscle fibers to the extracellular matrix through the dystrophin-associated glycoprotein complex (DGC). It functions as a molecular shock absorber during contraction, distributing mechanical stress across the sarcolemma (muscle cell membrane) and preventing membrane damage.
- In DMD, the dystrophin gene mutation (usually large deletions) causes a frameshift that produces no functional dystrophin whatsoever — the protein is completely absent.
- In BMD, the mutation preserves the reading frame, producing a truncated but partially functional dystrophin protein — this explains the milder phenotype and later onset.
Contraction-Induced Damage Cycle
- Without functional dystrophin, the sarcolemma is fragile and tears during normal muscle contraction — particularly during eccentric loading, when mechanical stress on the membrane is greatest.
- Membrane tears allow uncontrolled calcium influx into the muscle fiber. Excess intracellular calcium activates proteolytic enzymes (calpains) that degrade myofibrils and mitochondria, triggering a cascade of necrosis.
- Creatine kinase and other intracellular enzymes leak through the damaged membrane into the bloodstream — this is why serum CK is massively elevated in DMD and serves as the primary diagnostic marker.
- The immune system responds to necrotic fibers with macrophage infiltration and inflammation, further damaging adjacent fibers.
Regeneration Failure and Fibrotic Replacement
- Satellite cells (muscle stem cells) initially attempt to regenerate damaged fibers, and biopsies show a mixture of degenerating and regenerating fibers. However, the regenerated fibers also lack dystrophin and are equally vulnerable to contraction damage — creating a relentless cycle of damage and failed repair.
- Over time, the regenerative capacity of satellite cells is exhausted. Dead muscle fibers are replaced not by new muscle but by fibrotic connective tissue and adipose tissue (fatty infiltration).
- Pseudohypertrophy — the calves appear large and firm, but the apparent bulk is fat and connective tissue replacing muscle. Palpation reveals firm, dense tissue that is paradoxically weak — a defining clinical finding of DMD.
Secondary Complications
- Contractures: As muscles weaken asymmetrically, the stronger antagonists pull joints into fixed positions. The most common contractures are ankle plantarflexion (Achilles tendon), knee flexion, hip flexion, and elbow flexion. Contracture prevention is the primary goal of massage therapy in MD.
- Scoliosis: Progressive trunk muscle weakness leads to spinal collapse — scoliosis develops in virtually all DMD patients after loss of ambulation, often requiring surgical fixation.
- Cardiomyopathy: Dystrophin is also expressed in cardiac muscle. Progressive dilated cardiomyopathy develops in most DMD patients (and some BMD patients), becoming a significant cause of death.
- Respiratory decline: Diaphragm and intercostal weakness reduces vital capacity progressively; respiratory failure is the leading cause of death in DMD. Nocturnal hypoventilation precedes daytime respiratory compromise.
Signs and Symptoms
Duchenne Muscular Dystrophy (DMD) — Progressive Stages
| Stage | Age Range | Key Features |
|---|---|---|
| Early ambulatory | 2–5 years | Delayed walking milestones; frequent falls; difficulty running, climbing stairs, and rising from the floor; Gower's sign positive; pseudohypertrophy of calves begins; waddling gait; toe-walking |
| Late ambulatory | 6–10 years | Progressive proximal weakness — difficulty rising from chairs, climbing stairs; increasing lordosis to compensate for hip extensor weakness; contractures developing at ankles, knees, and hips; progressive difficulty walking |
| Non-ambulatory (early) | 10–14 years | Wheelchair-dependent; scoliosis develops rapidly; upper extremity weakness progresses; contractures accelerate; respiratory function begins to decline |
| Non-ambulatory (late) | 15+ years | Severe scoliosis; respiratory failure requiring ventilatory support; cardiomyopathy; complete dependence for ADLs; cognition is intact |
Becker Muscular Dystrophy (BMD)
- Similar pattern to DMD but milder and later onset (ages 5–15)
- Ambulation preserved into the 20s–30s or later
- Cardiomyopathy may be the presenting or most significant feature in some patients
- Pseudohypertrophy present; CK elevated but less dramatically than DMD
Key Clinical Findings Across Types
- Gower's sign: The child rises from the floor by "walking" the hands up the thighs — compensating for hip extensor and quadriceps weakness by using the arms to push the trunk upright. Gower's sign is the most tested clinical sign for DMD.
- Pseudohypertrophy: Calves (and sometimes deltoids and tongue) appear enlarged but are weak — firm palpation reveals dense tissue that is not true muscle bulk
- Proximal-before-distal weakness: Hip girdle weakens before shoulder girdle; shoulder girdle before distal extremities; distal hand and foot function is preserved until late stages
- Sensation is completely intact — MD affects muscle fibers only, not nerves; this is a critical clinical distinction from neurological conditions and means the client can provide reliable pain and pressure feedback
- Waddling (Trendelenburg) gait: Bilateral hip abductor weakness produces a characteristic side-to-side lurch; lumbar hyperlordosis compensates for weak hip extensors
Assessment Profile
Subjective Presentation
- Chief complaint: In children (via parent/caregiver) — "He can't keep up with other kids"; "He falls a lot"; "He can't climb stairs anymore"; "He has to use his hands to stand up." In adults with BMD or other types — "My legs are getting weaker"; "I'm having trouble with stairs and getting out of chairs"; known diagnosis with progressive functional decline
- Pain quality: Muscular aching from overworked compensatory muscles (lumbar extensors, upper trapezius, cervical extensors); joint pain at contracture sites (ankles, knees); no neuropathic pain (sensation is intact)
- Onset: Insidious, progressive from early childhood (DMD) or adolescence (BMD); no remissions or exacerbations — steady decline; family history of MD in many cases
- Aggravating factors: Eccentric loading activities (descending stairs, lowering into chairs) stress fragile muscle fibers the most; prolonged immobility accelerates contracture; fatigue from muscle overcompensation
- Easing factors: Rest relieves muscular fatigue; gentle movement prevents stiffness; adaptive equipment reduces mechanical demand on weakened muscles
- Red flags: Sudden onset of respiratory difficulty (shortness of breath, inability to lie flat, morning headaches from nocturnal hypoventilation) → medical referral for respiratory function testing. New cardiac symptoms (palpitations, exertional dyspnea disproportionate to activity level) → cardiology referral. Rapid functional decline exceeding expected progression → possible secondary cause.
Observation
- Local inspection: Pseudohypertrophy of calves (and sometimes deltoids) — visibly enlarged but paradoxically weak; muscle wasting in proximal limbs (thighs, upper arms); scoliosis visible in non-ambulatory patients; orthotic devices, wheelchair, or adaptive equipment may be present
- Posture: Pronounced lumbar hyperlordosis (compensating for hip extensor weakness); forward pelvic tilt; scapular winging (serratus anterior weakness in FSHD); thoracic kyphosis/scoliosis in non-ambulatory phase; ankle equinus from plantarflexion contracture
- Gait: Waddling (Trendelenburg) gait from bilateral hip abductor weakness — wide-based with exaggerated lateral trunk shift; toe-walking from Achilles contracture; hyperlordotic posture exaggerated during walking; Gower's sign positive when rising from floor or low chair
Palpation
- Tone: Hypotonic — reduced resting muscle tone as contractile tissue is replaced by fat and fibrous tissue. No spasticity or clonus (this is a primary muscle disorder, not a neurological condition). Compensatory muscles (lumbar extensors, upper trapezius) may be hypertonic from chronic overwork.
- Tenderness: Tenderness in overworked compensatory muscles — lumbar paraspinals, hip flexors (compensating for weak extensors), cervical extensors, upper trapezius from wheelchair posture; tenderness at contracture sites (Achilles tendon, IT band, hip flexor tendons); pseudohypertrophic calves are firm but not typically tender
- Temperature: No temperature abnormalities specific to MD; extremities maintain normal temperature (intact autonomic function); local warmth may be present over chronically overworked compensatory muscles
- Tissue quality: Pseudohypertrophic muscle — firm, dense, rubbery texture that feels like muscle bulk but generates no proportional strength. This is the palpation hallmark of DMD. Atrophied muscles feel soft, thin, and reduced in bulk. Fibrotic bands are palpable in chronically shortened muscles (hip flexors, plantarflexors). Fascial mobility is progressively reduced in immobile segments.
Motion Assessment
- AROM: Progressive loss of active range in a proximal-to-distal pattern — hip and shoulder movements lost before hand and foot movements; early in the disease, range may be mechanically full but weak; as contractures develop, both active and passive range decrease; Gower's sign is a functional AROM test (tests the ability to rise from the floor)
- PROM / end-feel: Firm/leathery end-feel at contracture sites — particularly ankle dorsiflexion (Achilles contracture), knee extension, and hip extension; PROM exceeds AROM significantly (weakness, not capsular restriction, limits active motion); normal elastic end-feel in joints not yet affected by contracture; joint hypermobility may be present in some types (FSHD)
- Resisted testing: Progressive proximal weakness — hip extensors and abductors weaken first, followed by shoulder abductors and flexors, then distal muscles; weakness is bilateral and symmetric; no pain on resisted testing unless compensatory strain is present; MMT grading documents progression over time
Special Test Cluster
| Test | Positive Finding | Purpose |
|---|---|---|
| Gower's sign (CMTO) | Child rises from floor by "climbing up" the legs with hands — bracing on thighs to push trunk upright | Confirms proximal hip extensor and quadriceps weakness; the classic DMD screening test |
| Trendelenburg sign (CMTO) | Pelvis drops on the unsupported side during single-leg stance | Confirms hip abductor (gluteus medius) weakness; positive bilaterally in MD |
| Adam's forward bend test (CMTO) | Rib hump visible on forward flexion | Screen for structural scoliosis secondary to trunk muscle weakness; present in most DMD patients after loss of ambulation |
| Deep tendon reflexes (CMTO) | Diminished or absent in severely wasted muscles; preserved in mildly affected areas | Reflexes are reduced proportionally to muscle bulk loss — distinct from the areflexia of GBS (where reflexes are absent even in non-wasted muscles) |
| Respiratory function screen (supplementary) | Reduced ability to count to 20 in one breath; paradoxical breathing pattern (abdomen rises while chest falls) | Screen for respiratory muscle decline; critical safety monitoring in advanced DMD/BMD |
Diagnostic confirmation note: MD is confirmed by genetic testing and/or muscle biopsy (dystrophin staining). Serum CK is massively elevated in DMD (10–100x normal). These are medical diagnostic tests, not MT assessment tools, but the MT should understand their significance.
Differential Assessment
| Condition | Key Distinguishing Feature |
|---|---|
| Spinal Muscular Atrophy (SMA) | LMN disease (anterior horn cell degeneration) — fasciculations present, tongue atrophy, hyporeflexia from denervation; MD has no fasciculations and reflexes proportional to muscle bulk |
| Guillain-Barre Syndrome | Acute onset, ascending weakness, areflexia; GBS is inflammatory and usually reversible; MD is chronic and progressive |
| Myasthenia Gravis | Fatigable weakness that improves with rest; normal muscle bulk; positive Tensilon test; MD weakness is constant and progressive, not fatigable |
| Polymyositis/Dermatomyositis | Inflammatory myopathy — elevated CK (like MD) but with skin rash (dermatomyositis), adult onset, and response to immunosuppressive treatment; MD does not respond to immunotherapy |
| Limb-Girdle Muscular Dystrophy | Same proximal weakness pattern but autosomal inheritance (affects both sexes); later onset; slower progression than DMD; genetic testing differentiates |
CMTO Exam Relevance
- CMTO Appendix category A4 (neurological conditions) — although MD is a primary muscle disorder, it is classified with neurological conditions in most exam frameworks
- Sensation is intact — the most important clinical distinction; MD affects muscle fibers, not nerves; clients can provide reliable feedback about pressure and pain
- Know DMD (absent dystrophin) vs. BMD (reduced dystrophin) and X-linked recessive inheritance — carrier mothers, affected sons
- Gower's sign is the most frequently tested clinical finding — understand the compensatory mechanism (arm push replaces hip extensor function)
- Pseudohypertrophy — firm/dense calves that are paradoxically weak; know that this represents fat and connective tissue replacement, not true muscle hypertrophy
- Know the proximal-to-distal weakness pattern and the contracture sequence (ankle → knee → hip)
- CK elevation is the primary laboratory marker — understand why it is elevated (enzyme leaks through damaged sarcolemma)
- Distinguish from neurological conditions: no fasciculations (vs. SMA/ALS), no fatigable weakness (vs. MG), no sensory changes (vs. peripheral neuropathy)
Massage Therapy Considerations
- Primary therapeutic target: contracture prevention and mobility maintenance — this is the single most important contribution of massage therapy to MD management; slowing contracture development directly preserves functional capacity and ambulation time; the target muscles are the antagonists to the contracture direction (ankle dorsiflexors, knee extensors, hip extensors)
- Intact sensation principle: Because MD does not affect the nervous system, the client can provide fully reliable pain and pressure feedback. This makes massage inherently safer than in neurological conditions with sensory disturbance — but does not eliminate the need for tissue-appropriate depth
- Fragility principle: Dystrophic muscle fibers are inherently fragile — the sarcolemma tears more easily than normal during mechanical stress. Moderate pressure is appropriate; aggressive deep tissue work may cause further fiber damage, particularly in muscles with significant fatty/fibrotic replacement. Adjust depth for tissue quality, not just pain feedback.
- Cardiac and respiratory awareness: In advanced DMD/BMD, cardiomyopathy and respiratory weakness are life-threatening comorbidities. Monitor respiratory rate and pattern; if respiratory distress develops during treatment, stop and assist. Prone positioning may be impossible in advanced respiratory compromise — side-lying or semi-reclined preferred.
- Steroid side effects: Many DMD patients take corticosteroids (prednisone/deflazacort) to slow disease progression. Side effects include osteoporosis, easy bruising, weight gain, and immunosuppression — adjust pressure for osteoporosis risk and infection precautions for immunosuppression.
- Contraindications: aggressive deep tissue work on dystrophic muscles (risk of further fiber damage); prone positioning in patients with significant respiratory compromise; resistance training with heavy loads (eccentric overload damages fragile fibers)
Treatment Plan Foundation
Clinical Goals
- Maintain available range of motion and slow contracture development at ankles, knees, and hips
- Reduce secondary tension in compensatory muscles (lumbar extensors, upper trapezius, cervical extensors)
- Support circulation in deconditioned extremities
- Provide comfort and psychosocial support in the context of progressive disease
Position
- Supine for lower extremity contracture work — allows direct access to ankle dorsiflexion, knee extension, and hip extension stretching
- Side-lying for trunk and hip work — preferred in patients with respiratory compromise or significant scoliosis
- Prone only if respiratory function permits and comfortable — useful for lumbar paraspinal and posterior hip access
- Wheelchair-based treatment may be necessary for patients who cannot transfer to a treatment table safely
Session Sequence
- General effleurage to lower extremities — assess tissue quality, identify contracture severity, and warm superficial tissues; note pseudohypertrophic areas (firm calves) and atrophied areas
- Sustained myofascial release to gastrocnemius-soleus complex — target the most common and most functionally significant contracture (plantarflexion); slow, sustained technique to elongate fibrotic tissue
- Gentle longitudinal stripping of hip flexors (iliopsoas, rectus femoris) — address hip flexion contracture that develops progressively; sustained pressure within tissue tolerance; depth adjusted for fragility
- IT band and lateral thigh release — address hip adduction/flexion pattern contributing to gait disturbance; foam roller work may supplement manual technique in ambulatory patients
- Compensatory pattern work — lumbar paraspinals (hyperlordosis overload), upper trapezius and cervical extensors (wheelchair posture), scapular stabilizers [especially relevant in FSHD]
- Gentle passive stretching of contracture sites — ankle dorsiflexion, knee extension, hip extension; sustained holds at end-range; [do not force against established bony contracture — work within available soft tissue range]
- Upper extremity work [non-ambulatory phase] — as upper extremity weakness progresses, address forearm and hand tension from adaptive equipment use; maintain wrist and finger mobility
Adjunct Modalities
- Hydrotherapy: Moist heat to contracture sites pre-treatment to improve tissue pliability — especially Achilles tendon, hip flexors, and hamstrings; heat is safe (no neurological heat sensitivity in MD); warm-up before stretching improves outcomes
- Joint mobilization: Gentle talocrural mobilization (dorsiflexion glide) after soft tissue release — directly targets the most critical contracture; Grade I–II in early contracture; limited utility once bony restriction develops; hip mobilization to maintain extension and abduction range
- Remedial exercise (on-table): Active-assisted ROM through available range in weakened muscles — therapist supports the limb while the client moves; gentle active ankle dorsiflexion repetitions after calf release to reinforce gained range; low-load sustained stretching (not ballistic); no eccentric overload — eccentric contractions are the most damaging to dystrophic fibers
Exam Station Notes
- Demonstrate understanding that MD is a primary muscle disorder with intact sensation — state explicitly that the client can provide reliable feedback
- Show assessment of contracture vs. weakness — distinguish firm end-feel (contracture) from empty end-feel (weakness) to determine treatment targets
- If pseudohypertrophy is present, identify and explain it — "The calves feel firm and dense, but strength testing shows weakness — this indicates muscle replacement by fat and connective tissue"
- Demonstrate depth adjustment for tissue fragility — state that aggressive deep work may damage dystrophic fibers
Verbal Notes
- Explaining pseudohypertrophy: "Your calves feel quite firm, which might seem strong, but the firmness comes from changes in the muscle tissue. I'll work gently through this area to help maintain flexibility."
- Stretch communication: "I'm going to hold a gentle stretch at your ankle. This might feel tight but shouldn't be painful. Tell me if it becomes uncomfortable — holding the stretch gently is more effective than pushing through pain."
- Respiratory monitoring: if respiratory compromise is present — "If you feel short of breath at any point, or it's easier to breathe in a different position, let me know right away and we'll adjust."
Self-Care
- Daily sustained stretching of ankle dorsiflexors, hip extensors, and knee extensors — caregiver-assisted or self-performed; sustained holds of 30+ seconds; the single most important home intervention for preserving ambulation time
- Night splints for ankle dorsiflexion — maintain stretch position overnight to counteract daytime plantarflexion tendency; compliance is critical
- Activity maintenance — remain as active as tolerated; swimming and water-based activities reduce gravity load while maintaining movement; avoid high-impact and eccentric overload activities
- Positioning in wheelchair — regular weight shifts, proper seating alignment to slow scoliosis progression; avoid prolonged hip flexion without extension breaks
Key Takeaways
- Muscular dystrophy is a primary muscle fiber disorder — sensation is completely intact, allowing reliable client feedback; this distinguishes MD from all neurological conditions
- DMD (absent dystrophin) and BMD (reduced dystrophin) are both X-linked recessive — affecting males, carried by mothers; the difference is gene reading frame (frameshift vs. in-frame deletion)
- Pseudohypertrophy — firm, dense calves that are paradoxically weak — is the palpation hallmark; the tissue is fat and connective tissue replacing muscle
- Gower's sign (rising by "climbing up" the legs) is the classic functional test for proximal hip extensor weakness in DMD
- Contracture prevention is the primary MT goal — ankle plantarflexion, knee flexion, and hip flexion contractures are the most functionally limiting; sustained stretching is the most effective intervention
- Dystrophic muscle fibers are mechanically fragile — aggressive deep tissue work risks further fiber damage; moderate pressure adjusted to tissue quality
- Cardiac involvement (cardiomyopathy) and respiratory decline are the leading causes of death — monitor respiratory status and position accordingly