Duchenne Muscular Dystrophy Lower Limb problems affect thousands of families throughout the world—and are perhaps one of the most visible and life-changing aspects of the disorder.

Whether it’s the first subtle signs of muscle weakness in young children or the gradual loss of walking ability in your teens, the involvement of the DMD Lower limbs impacts every detail of daily life.

Knowing what is really going on in the calves, hips and legs allows families, caregivers and those interested to better understand the jargon used in medical reports and research.

Here, the underlying principles are explained—how the lower limbs are involved, how this development progresses and how what we have today is translated into everyday management practice.

Duchenne Muscular Dystrophy Lower Limb Weakness Principles

Duchenne MD is a disease resulting from changes within the gene for the structural muscle protein dystrophin.

Without dystrophin there is increased degradation, and a greater rate of loss of muscle fibers.

The main affected areas early in the course of the disease tend to involve the hip flexors, quadriceps, calf muscles and the muscles around the pelvis—that’s why most of your child’s initial gait problems will be some degree of abduction, waddling gait and difficulty rising from the floor.

The significance of early gait changes and the Gowers’ sign

Early in the disease it is often the sign of DMD most likely to have been picked up by mothers and health professionals—know as the Gowers’ sign, children will ‘walk up’ their own legs, pushing on their hands as they come to the end of a sit to stand, to use the technique of one of the smartest and most able 3-year-olds.

This interesting lurch forward is a part of the struggle of the weak hip and thigh muscles; however, it clearly shows the weakness before later features develop.

Along with this, a waddling gait develops, as the pelvis rock from side to side with the step, because the gluteus medius cannot support the pelvis as well as non-affected children.

Calf pseudohypotrophicity—more than you think

Many people have been surprised when they realize how large the calves in DMD look—and this phenomenon is known as pseudohypertrophy.

It results from the loss of muscle tissue, and its subsequent replacement by fat and connective tissue.

The strength you can feel doesn’t match the size of the calves. If you notice the two in parallel, it can delay diagnosis.

You will feel the calves are quite firm, but the underlying strength will be weak.

The progression of walking and what happens after

Ambulation, the ability to walk independently, is usually lost at a mean age of 9.7 years in boys with DMD—for example, depends on the mutation involved, steroid use there.

For your son, the huge psychological and physical shift to a chair can be daunting.

However, this isn’t the end of the lower limb story—they can all offer a sigh of relief, because the subsequent loss of walking triggers many other important issues.

This is because skeletal deformities and contractures become significant once a child fails to ambulate on a daily basis.

Contracture formation affecting the hips, knees and ankles

Controls of length change will have been ongoing since the earliest months.

If a part of your child’s body isn’t being stretched through normal movement and whole body repositioning, this same process will affect muscle shortening and the formation of a contracture.

In legs, the problem most commonly develops in hip flexors, hamstrings and the Achilles tendon.

The tight Achilles can cause toe-walking before loss of ambulation has occurred, through to pressure areas and eventual saddle deformities with fixed hip flexion in the wheelchair.

Physiotherapy, orthotic devices and some surgical procedures all play their part in trying to delay the effects of this process.

Scoliosis and the link with the lower limb in DMD

Therefore, it is perhaps no great surprise, that once the active position of walking has stopped, the pelvic and spinal muscles no longer being used are unable to support the stresses that are placed upon the spinal column on a daily basis.

During the teenage years a curve of the spine develops between the hips and shoulders in over 90 of non-wheelchair dependent boys, and there is definitely a developmental link which directly involves the muscles of the lower limbs and pelvis.

Seating strategies in the wheelchair to maintain spinal balance become very important, and the monitoring of scoliosis as the child matures essential.

Managing Duchenne Muscular Dystrophy Lower Limb Problems

There is an important team involved in the management of children with DMD and their lower limbs—including physiotherapists, orthopedic surgeons, rehabilitation specialists and orthotists.

The objectives of management can be said to be, to maintain function as long as possible, reduce pain and discomfort and maximize quality of life.

Physiotherapy and orthotic devices

Physiotherapy is an element that should probably be introduced right from the start and remain a key feature throughout your child’s life with DMD.

Stretching exercises are prescribed in relation to the hip flexors, hamstrings (knee flexors) and ankle plantar flexors.

Ankle-foot orthoses (AFOs)—might be recommended at night to stretch ankle joints and slows down Achilles tendinal shortening by maintaining ankle dorsiflexion throughout the night.

Ankle AFOs have also been used during the day to support ambulation in suitable boys to support them when walking.

The size of any orthosis needs to be monitored frequently to ensure that they continue to fit properly and inappropriately fitted orthoses can be very damaging to already weak muscles.

The benefit of corticosteroid use on the lower limb

The use of corticosteroid medication, deflazacort or prednisolone, is thought to prolong the term of independent walking by around two to three years.

They have not been able to cure the problem of absent dystrophin; however, the inflammatory cycle that it appears to trigger and that precipitates your child’s loss of function can be affected.

This is important because an extra two or three years of walking can delay contractures by the minimum of a year, and often much longer, and make the presence of scoliosis less severe.

The side effects and risks are also under constant review, and weight gain, osteoporosis and sleep disturbance as well as the emotional effects must all be carefully monitored.

In the face of the investigation into the efficacy of the newer gene-based approaches to DMD treatment, glucocorticoid and steroid use has become a reasonably standard approach to ensure that the best of current management of lower limb advantage is achieved.

Duchenne Muscular Dystrophy explored—from the modifications of gait and pseudohypertrophy of the lower limbs in DMD initially, through to contractures, loss of ambulation and the means used currently.