What is limb length discrepancy?
Limb length discrepancy (LLD) or limb length inequality refers to a condition where one arm or one leg is shorter than the other.
Differences in arm length are less likely to affect normal function compared to differences in leg length, which affects day-to-day activities such as walking and playing sports.
The difference in leg length can vary widely, from less than an inch to several inches. Significant differences can affect a person’s posture while standing or walking. This may lead to problems in the hip, knee and ankle and cause scoliosis (abnormal curvature of the spine).
Types of limb length discrepancy
LLD can be categorised as a static or progressive deformity:
- Static - Where the discrepancy stays the same. This could be due to a malunion of a fracture (when a fractured bone heals in an abnormal position) of the lower limb bones.
- Progressive - Where the discrepancy can worsen with further growth. This could be due to an injury to the growth plate; or it could be caused by a condition present from birth (congenital).
What are the symptoms of limb length discrepancy?
Symptoms of leg length discrepancy varies based on the difference in leg length, its cause and the presence of other health conditions.
- Problems with gait (pattern of walking), such as a limp, walking on toes or leaning to one side
- Abnormal posture, such as a tilting shoulder or having the ankle on the shorter leg chronically hyperextended
- Pain in the ankles, knees, hip, or back as a result of compensating for the difference in leg length
- Functional scoliosis (abnormal curvature of the spine)
- Back pain
What causes limb length discrepancy?
Discrepancies in leg length can exist from birth. These may be due to conditions that interfere with the alignment of the hip, such as developmental dysplasia of the hip (DDH), or there may be no known cause.
Other causes of leg length discrepancy include:
- Fractures or trauma to the bone can affect its growth.
- For example, bone that has been broken in multiple places, with severe damage to the skin and muscle, can heal shorter than it was before.
- However, a child with a broken leg bone can sometimes go through accelerated growth that causes it to become longer than the bone in the other leg. This is more common in young children who experience fractures of the thigh bone.
- Bone infection (osteomyelitis) can damage the growth plate and lead to limb length discrepancies.
- Bone tumours and its treatment can affect the rate of bone growth, leading to discrepancies in length.
- Paralytic disorders like cerebral palsy can affect alignment and posture, and cause discrepancy.
Leg length discrepancies can lead to several complications. Left untreated, the patient may experience:
- Back pain
- Pain from osteoarthritis
- Functional scoliosis
- Problems with gait
- Joint problems
Treatment needs to be customised to each individual patient. Some patients may only require a simple insert into the shoe, while others may require surgery.
Surgery will be recommended only if other treatment options are not successful in correcting the leg length discrepancy. Before recommending surgery, your doctor will take into consideration any potential pitfalls and complications that may occur.
It is best to consult with an orthopaedic surgeon for the condition.