Leg-length discrepancy (LLD) is a condition concerning the difference in leg length which can cause issues such as disruption to normal gait patterns or pain to the spine and lower extremities.
This musculoskeletal condition may be congenital, the result of a major injury such as a fracture, or from post-operative for procedures such as hip-replacement surgery (Reisman). While any amount of discrepancy may seem abnormal, LLD is rather common for about 65 to 70 percent of the general population with varying levels, from mild to severe cases that require surgical intervention (Pereira et al.). For those with mild LLD, the onset is often noticeable in active individuals, such as runners, individuals with occupations requiring them to weight bear, or individuals who take on a sudden increase in their level of physical activity. The signs and symptoms of mild LLD are similar to other musculoskeletal conditions, rendering it difficult to determine a diagnosis. There are two types of LLD: structural, involving the length of the long bones, or functional, involving the musculature of the leg (Kennedy). Treatment of LLD is dependent on the type diagnosed, the level of severity, and should be focused on the whole physical functionality of an individual, guided by the chief complaint of symptoms and patient goals.
Diagnosing leg-length discrepancy (LLD) can be difficult due to the often insidious nature of the onset of symptoms (Kennedy). Common symptoms include lower back pain (LBP), hip pain, knee pain, and pain at the foot and ankle (Rigsbee). Leg-length discrepancy can present certain signs based on the type of LLD involved, or as a secondary condition. Common signs include a lengthening of the iliotibial band at the medial femoral condyle of the longer leg, paraspinal deviations such as scoliosis, and ankle pronation with the shorter leg (Rigsbee). These signs also contribute to a 90% incidence of weak hip strength in abduction and adduction, which is assessed through methods of diagnosis and can be one factor to consider for prescribed physical therapy treatment (Rigsbee).
To assess leg-length discrepancy, there are several methods, though some methods are deemed more accurate and reliable for certain types of LLD. A common method of assessment is simple observation, a visual comparison of a patient’s lower extremities when standing (weight-bearing), lying supine (on the back), and with a gait analysis. Another common and simple method utilizes a measuring tape, measuring from the anterior superior iliac spine (ASIS, otherwise known as the prominent palpable point on the hip) to the midpoint of the medial malleolus of the same leg (Kennedy). Measuring leg lengths with a tape measure is helpful in determining if LLD is functional, which can and often presents differently from structural LLD, and it factors the height of the foot that can contribute a leg length difference (Sabharwal and Kumar). Tape measurements are often used to assess the actual leg length difference without radiographs (Sabharwal and Kumar). If a LLD is determined, standing blocks can help to measure the amount of discrepancy, as well as to provide a guideline in prescribing an amount of correction (with lifts) in order to relieve any symptoms related to the discrepancy (Kennedy). Imaging can also be used to obtain an accurate measure of discrepancy, especially for structural LLD.
Determining either of the two types of leg-length discrepancies requires the use of certain types of assessment methods as previously described, as each type of LLD presents differently. Functional LLD is sometimes known as false LLD, because the long bone of the legs may not actually be of significantly different lengths, but the signs and symptoms of functional LLD could be attributed more to the mechanical structures of the legs (Rigsbee). Structural LLD is sometimes known as true LLD, which is obviously apparent in radiographs of the femur or tibia (Rigsbee). One important factor that a clinician will determine before making any judgment on the type of LLD involved is the presence of asymmetry, whether it is visually assessed, apparent in muscular strength and flexibility, or through imaging (Rigsbee). Functional LLD often presents with spinal issues, muscular weaknesses, lack of flexibility in the ligaments, and restricted movement in the joints of the lower extremities (Kennedy). Signs and symptoms of functional LLD often are results of (secondary conditions) or actual contributors to mechanical changes in the limb (Kennedy). One example would be unilateral, chronic contractions of spinal muscles, which can cause scoliosis, or in a mild sense, insidious back pain. Structural LLD is the result of anatomically short limbs, usually because of the length of the long bones of the leg (Pereira et al.). It is important for a clinician to use all of diagnostic methods necessary to determine the type of LLD a patient may have because the results will be useful in developing an effective treatment plan.
Structural LLD is best determined by accurate and reliable x-ray methods (Knutson). In a review on clinical decision-making, a study found that structural LLD was not clinically significant (that is, it did not warrant evasive surgical corrective treatment) until it reached a difference of about 20 mm (Knutson). This type of LLD has an additional name, loaded leg-length alignment asymmetry, because the symptoms of LLD are apparent when the patient is weight-bearing (Knutson). The most common effect of structural LLD is pelvic torsion, which results from the unequal attributes of the legs. However, a study found in the aforementioned review found that pelvic torsion did not correlate with chronic low back pain (Knutson), which may further indicate the adaptive nature of the human body. There is a strong association between structural LLD and osteoarthritis in the supero-lateral region of the hip (anatomically long side) (Knutson).
Functional LLD can also be known as unloaded leg-length asymmetry because while a patient may not be weight-bearing, the symptoms of LLD are still apparent, as the muscular and ligamentous structures of the leg can still affect a patient (Knutson). Functional LLD is often assessed for neuromuscular dysfunction (Knutson). Neuromuscular dysfunction is a disorder that can contribute many affects but one example would be neurological insufficiencies to certain innervated muscles. According to an article on Medlineplus.gov, neuromuscular disorders may contribute to a weakness, causing atrophy, and cramping (e.g. back pain), and joint issues which limit movement. Thus, these conditions related to many neuromuscular dysfunctions may and can contribute to a functional LLD, another important factor that a clinician should apply in a treatment plan.
The treatment plan for leg-length discrepancy highly depends on the outcome of assessment by a clinician, who should approach the treatment plan with a focus on treating the biomechanics involved, not necessarily the LLD directly (Rigsbee). The goal or goals for treating a patient with LLD depends on what the patient can tolerate, what is comfortable for the patient, and to achieve efficient functionality without pain (Kennedy). Gait analysis, although used as an assessment tool prior to treatment, is important during and after treatment, so that a regular assessment of any changes can be made, especially in regards to the effectiveness of a current treatment plan for a practical function. A clinician should remember that the human body is highly adaptive. Structural LLD, especially such that has been a life-long experience for a patient, will not always present with painful symptoms because the body would have developed compensations for structural differences over time (Rigsbee). For this case, during treatment, addressing biomechanical issues is important because, while structural LLD can only be corrected surgically, the symptoms are the primary issue for the patient, thus only those issues should be addressed for achievable progression.
The biomechanical aspects to focus on, regarding leg-length discrepancy, would include bilateral and sufficient muscular strength, flexibility at the musculotendinous and ligamentous areas, and functional, full range of motion (Rigsbee). Examples of common treatment methods used in a physical therapy clinic would include spinal stabilization exercises (in flexion and extension) to provide support and alleviate pain and weakness caused by unilateral stress, and lower extremity and spinal stretches, to provide additional relief to unilateral stresses caused by hypertonicity of muscles, which is an over-compensation by being in a state of chronic contraction. Soft tissue mobilization, also known as massages, can help to relieve painful symptoms, but in order for a patient to regain pain-free independence, exercises that focus on equal strength, flexibility and full range of motion should be utilized reasonably. There are no special exercises specific to LLD since the symptoms of LLD are commonly seen in other conditions. Thus, a clinician, such as a physical therapist, can use practically any exercise to address common symptoms of LLD, such as back pain and lower-extremity joint pain.
Active individuals are often those who are diagnosed with a leg-length discrepancy and experience symptoms with an insidious onset, but the initial changes in gait are more evident early on or with increased, load-bearing activities (Pereira et al.). Incidences in runners and persons with occupations that are physically demanding, such as military personnel, are very common. A study which assessed whether or not mild leg-length discrepancy had any kinetic effect on runners’ gait showed that there were kinetic changes, compared to a normal running gait (Pereira et al.). These changes were not clinically significant until about 25 mm in adult runners (Pereria et al.). An internist provided anecdotal evidence that lifts (which are placed within or are part of a shoe) can alleviate knee and back pain on weight-bearing by adding partial correction to a LLD of a seasoned runner (Reisman). Mild LLD affects age groups differently. In the same study mentioned, research found that young children with mild LLD experienced no discrepancy in their gait, while older children experienced gait discrepancies at a difference of 2.33 cm, notably with increased flexion in the longer leg and foot supination in the shorter leg (Pereira et al.). For adults, gait discrepancies could be seen in a leg-length difference of about 1 cm during weight-bearing activity. From this study, one can conclude that not all mild LLD needs to be addressed, and it is not until it is a deterrent to normal functioning that one requires active treatment. Runners in this study were able to adapt to their minor LLD by utilizing physical compensatory mechanisms for the deviations of their running gait in order to achieve a symmetrical gait, which will naturally avoid painful symptoms (Pereira et al.). These mechanisms were sufficient enough for runners to function without pain and without additional support (i.e. lifts), further supporting the efficient adaptability of the human body.
The natural ability of the human body to develop enough efficiency to function around what may be deemed an abnormality, such as leg-length discrepancy, should be an underlying factor in the consideration of the treatment related to any type of LLD. Many people are diagnosed with some form of LLD, most of which are mild. Within this sample of the population with mild LLD, many go about activities of daily living (ADLs) asymptomatically unless there has been a drastic change in lifestyle, such as significantly increasing physical activity. Furthermore, LLD may go undetected in a person’s life. Thus, it is important to treat the symptoms of LLD, and not focus on treating the condition of LLD unless the severity warrants invasive procedures such as surgery. In treating the symptoms of LLD, re-establishing or maintaining bilateral muscular strength, ligamentous and tendinous flexibility, full range of motion, all without pain inasmuch as it is possible, should be the actual focus when prescribing a treatment regimen. Just as much as leg-length discrepancy is vague in nature, the recommended exercises or treatment methods are numerous, depending on the type and severity of symptoms involved. A physical therapist is one of the professionals within a pathology team that can assess the musculoskeletal aspects of a particular condition and prescribe some of the most effective treatments involving leg-length discrepancy.
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—. “Anatomic and Functional Leg-Length Inequality: A Review and Recommendation for Clinical Decision-Making. Part II, the Functional or Unloaded Leg-Length Asymmetry.” Chiropractic and Osteopathy 13.12 (2005): n. pag. Web. 7 April 2010.
“Neuromuscular Disorders.” Medlineplus.gov. The National Library of Medicine, 14 April 2010. Web. 15 April 2010. .
Pereira, Carla Sonsino, and Isabel de Camargo Neves Sacoo. “Is Structural and Mild Leg Length Discrepancy Enough to Cause a Kinetic Change in Runners’ Gait?” Acta Ortopédica Brasileira 16.1 (2008): 29-31. Web. 24 March 2010.
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Sabharwal, Sanjeey, and Ajay Kumar. “Methods for Assessing Leg Length Discrepancy.” Clinical Orthopaedics and Related Research 466.12 (2008): 2910-2922. Web. 24 March 2010.