Lower Limb Problems in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe, progressive X-linked neuromuscular disorder caused by mutations in the dystrophin gene. The resulting absence or severe deficiency of dystrophin protein leads to muscle membrane fragility, chronic inflammation, fibrosis, and fatty replacement of muscle tissue. Although the disease eventually affects nearly all skeletal muscles, the lower limbs are typically the first and most functionally devastating site of involvement. Proximal lower-limb weakness, characteristic gait abnormalities, progressive contractures, and eventual loss of ambulation define much of the clinical course and daily disability experienced by affected individuals, who are almost exclusively boys.

Muscle weakness in DMD follows a proximal-to-distal pattern and begins in the pelvic girdle and thigh musculature. Hip extensors (gluteus maximus), hip abductors (gluteus medius and minimus), and the quadriceps are among the earliest and most severely affected muscles. This selective weakness produces classic compensatory postural and gait strategies. Children develop an exaggerated lumbar lordosis and anterior pelvic tilt to keep the center of gravity aligned over the base of support when hip extensors can no longer stabilize the pelvis. Weak hip abductors produce a Trendelenburg or waddling gait, while quadriceps weakness leads to knee hyperextension or "locking" in stance to prevent collapse. Toe-walking emerges early, driven by relative strength (or later tightness) of the plantarflexors and progressive loss of ankle dorsiflexion. These gait deviations—wide base of support, increased lateral trunk sway, shortened stride length, and reduced cadence—appear between ages two and six and progressively worsen.

A striking physical finding is calf pseudohypertrophy. The gastrocnemius and soleus appear enlarged, yet imaging and histology reveal that the bulk is largely fibrofatty tissue rather than functional muscle. Despite this enlargement, the calf muscles gradually lose power and, more importantly, become fibrotic and shortened. Ankle plantarflexion contractures are therefore among the earliest musculoskeletal complications. Over time, contractures also develop in the hip flexors, tensor fascia latae, and hamstrings, limiting hip and knee extension. Once ambulation is lost, usually between ages 10 and 14 (later with modern corticosteroid therapy), fixed equinovarus foot deformities, knee flexion contractures, and hip flexion–abduction contractures become pronounced. These deformities interfere with comfortable seating, transfer ability, skin integrity, and the fitting of orthoses or wheelchair footplates.

The functional consequences are profound. Early difficulty rising from the floor (Gowers’ sign), climbing stairs, and running gives way to frequent falls, reduced walking distance, and eventual wheelchair dependence. Loss of independent ambulation accelerates further contracture formation because of prolonged static positioning and reduced passive range of motion. Secondary effects include disuse osteoporosis, increased fracture risk (especially of the femur and tibia), and contribution to progressive neuromuscular scoliosis through pelvic obliquity and asymmetric lower-limb contractures. Lumbar hyperlordosis itself, while initially compensatory, eventually impairs balance and gait efficiency.

Management of lower-limb problems is multifaceted and aims to preserve function, delay contractures, and maintain quality of life. Daily passive stretching of the gastrocnemius–soleus complex, hamstrings, and hip flexors remains a cornerstone of care, ideally performed several times per day. Night-time ankle-foot orthoses (AFOs) in a neutral or slightly dorsiflexed position help control progressive equinus. Standing frames and supported standing programs promote bone health and counteract hip and knee flexion contractures. During the ambulatory phase, some clinicians employ articulated or solid AFOs cautiously; after loss of ambulation, knee–ankle–foot orthoses (KAFOs) or hip–knee–ankle–foot orthoses may assist with positioning and limited standing. Corticosteroid therapy, now standard, delays loss of ambulation by several years and reduces the severity of contractures and scoliosis.

When conservative measures fail and residual strength is still adequate, selective soft-tissue surgery (Achilles tendon lengthening, sometimes combined with tibialis posterior transfer) can improve foot position and temporarily prolong walking or improve seating comfort. Surgery on the hips or knees is generally avoided because of the high risk of rapid recurrence and further functional loss. After loss of ambulation, surgical goals shift toward comfortable seating and prevention of pressure ulcers rather than restoration of gait. Regular monitoring of joint range of motion, gait, and spinal alignment allows timely intervention.

Lower-limb involvement is the primary driver of early disability in Duchenne muscular dystrophy. Proximal weakness produces characteristic compensatory gait patterns, while progressive fibrotic contractures of the ankle, knee, and hip ultimately terminate independent walking. Although the underlying genetic defect remains incurable, systematic physiotherapy, orthotic management, corticosteroid treatment, and judicious surgery can meaningfully delay functional decline, preserve comfort, and improve daily participation for individuals living with this devastating disease. Continued research into disease-modifying therapies and better contracture-prevention strategies holds promise for further extending the ambulatory years and reducing the burden of lower-limb deformity.

Craig Payne is a University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger and a dad.