Evaluation for subtle structural defects of the lower limb

INTRODUCTION — Subtle structural defects of the lower limb often predispose or contribute to the development of cumulative movement disorders or repetitive strain injuries [1]. Careful examination to detect these defects should be part of the management of patients with disorders such as tendinitis, bursitis, stress fractures, compartment syndromes, and plantar fasciitis. (See appropriate topic reviews).

Long distance runners, for example, may have complaints that result from the accumulated impact loading of this activity [2-4]. These problems are often related to biomechanical overuse in patients with minor structural disorders. Malalignments with mechanical disadvantages, muscle contractures, and the use of untrained muscles may lead to biomechanical failure [3].

Lateral asymmetry is a common cause for many regional pain disorders and may predispose to sport injury and other lower limb pain and injury. Features include facial asymmetry, scoliosis, a short leg, and flat feet

A careful examination includes evaluation of the appearance of the lower extremity when the patient is standing, walking, rising, sitting, and lying. It also includes evaluation of the patient's shoes.

STANDING EXAMINATION — Congenital abnormalities of alignment and joint mobility may be evident while the patient is standing with the feet slightly apart and parallel (pointing directly forward). Genu recurvatum — Excessive backward motion during active knee extension may be an isolated finding or part of generalized multidirectional joint instability. Hyperextension of the knee, excessive backward knee joint mobility, or patella alta (a high-riding patella) can contribute to recurrent knee dislocation. In severe cases, leg braces may be required. The hypermobility syndrome should be considered if knee pain, knee hyperextensibility, and flat feet are present (show picture 2). (See "Clinical manifestations and treatment of the hypermobility syndrome"). Joint hypermobility — Children with hypermobility may have joint pain. This was illustrated in a study of juvenile hypermobility syndrome in 125 children (64 females) who had hypermobile joins and pain that had been present for longer than three months [5]. Hypermobility had only been recognized as a possible cause of joint complaint in 10 percent. The average age at onset of symptoms was 6.2 years and age at diagnosis 9.0 year, indicating a two- to three-year delay in diagnosis.

The major presenting complaint was arthralgia in 74 percent, abnormal gait in 10 percent, apparent joint deformity in 10 percent, and back pain in 6 percent. Mean age at first walking was 15.0 months; 48 percent were considered "clumsy" and 36 percent as having poor coordination in early childhood. Twelve percent had "clicky" hips at birth and 4 percent actual congenitally dislocatable hips. Other features that were noted in association with joint hypermobility were: recurrent joint sprains (20 percent) and actual subluxation/dislocation of joints (10 percent); problems with handwriting tasks (40 percent), major limitations of school-based physical education activities (48 percent), other physical activities (67 percent). Easy bruising and significant periods of schooling missed because of symptoms were also noted in many children. Abnormal patellar alignment — Patellar alignment should be viewed in relation to the tibial tubercle. From the frontal aspect, the patellae may point away from the midline, denoting lateral patellar subluxation ("grasshopper eye patellae"); this often occurs in association with chondromalacia patellae [6]. External rotational malalignment with inwardly pointing patellae may predispose to patellofemoral subluxation [7]. (See "Evaluation of the adult patient with knee pain").

The clinical significance of abnormal patellar alignment is uncertain. Many people with such subtle abnormalities are asymptomatic. The lack of an association between patellar alignment problems and anterior knee pain was illustrated in two studies. In one of these studies of 40 young women who had patellofemoral pain syndrome, no significant differences were found between the most symptomatic knee and the least symptomatic knee, nor between patients and controls with regard to leg alignment, Q-angle, and leg-heel alignment [8]. Pain was associated with increased activity, suggesting that chronic overloading and temporary overuse of the patellofemoral joint, rather than malalignment, contributed to patellofemoral pain.

In the second study of 33 patients with patellofemoral pain and matched controls, no difference was found in measures of patellar tilt, superior migration of the patella, or patellar facet angle at rest or with quadriceps contraction [9].

However, malformations or degenerative changes of the patella can lead to patellofemoral pain. Arthroscopy with debridement is necessary in some cases. However, I advise patients to first try a short arc resistance quadriceps exercise under the supervision of a therapist or trainer. Miserable malalignment syndrome — The so called miserable malalignment syndrome is a constellation of excessive femoral anteversion, excessive tibial outward rotation, and patellofemoral pain. When evaluating patients with patellofemoral pain, it is important to assess the rotational profiles of the femur and tibia. Although an uncommon cause for patellofemoral pain, treatment has been proposed consisting of ipsilateral outward femoral osteotomy and inward tibial osteotomy. A series study of 27 limbs in 14 patients reported a satisfactory five year outcome in all operated patients [10]. Genu varum (bowleg) or genu valgum (knock-knee) — The terms varus and valgus refer to inward or outward deviation of the foreleg from the midline, respectively. However, discussions in the literature have emphasized that these commonly used terms are inaccurate and inadequate [11]. Thus, it is usually best to add additional descriptions (eg, bowleg, knock-knee) when defining changes related to these anatomic deviations.

Genu valgum is common in children and often resolves spontaneously. However, it may predispose to lateral patellar dislocation or displacement, and later in life to osteoarthritis. (See "Risk factors for and possible causes of osteoarthritis"). If present at age six or older, gait may be impaired. Bracing and strength training can sometimes improve the angulation or at least prevent it from worsening. Surgical revision with osteotomy during childhood has been suggested for children [12]. Some adults may also benefit from osteotomy if they have not developed advanced osteoarthritis of both lateral and medial compartments of the knee.

When painful genu valgum or genu varum (less commonly) occurs in an adolescent, rickets should be a consideration. Although rare in developed countries, rickets still occurs in rural and third world populations [13,14]. Toe deformities — Toe deformities such as hallux valgus and metatarsus primus varus of the first toe (the first metatarsus is shortened and deviated to the midline, and the toe is rotated slightly medially as noted by the slant of the toe nail) are evident during the standing examination. Toe crowding should also be observed.

WALKING EXAMINATION — The patient should be observed while walking toward and away from you with the legs uncovered. The feet may point away 30 degrees from the midline. Deformities such as a short leg, osteoarthritis of a hip, leg torsions, genu recurvatum, flatfeet, or neurologic disturbances may become apparent during this examination.

Pes planus (flatfoot) may give rise to knee region discomfort. The flatfoot is accompanied by pronation, a tilting outward of the foot, and valgus deviation of the heel (show picture 3). This can be seen best by inspecting the foot from behind the standing patient.

From the frontal view, a line carried from the midpoint of the patella down the anterior spine of the lower tibia should project forward through the web between the second and third toes. The heel should be aligned parallel to the longitudinal axis of the distal tibia when viewed posteriorly. The plane of the metatarsal heads should be perpendicular to the heel [2].

SITTING AND RISING EXAMINATION — The patient should be observed while rising from a seated position without the use of hands for assistance. This is a simple test of the integrity and strength of the quadriceps extensor mechanism, but may also suggest knee disorders located in the patellofemoral region or primary muscle disease. Lateral patellar displacement or subluxation may be observed as the seated patient straightens the knee and the patella moves outward instead of straight upward; this is often called the "J" sign. The laterally tilted patella should be manually correctable when the patient is lying supine. In addition, the patella should be displaceable medially about 1 cm from its resting position when the knee is flexed to 30 degrees. Inability to perform these maneuvers suggests that the lateral patellar retinaculum is abnormally tight; these patients may benefit from stretching exercises [15]. (See "Rehabilitation program for the lower limb"). Surgical release of the tight tissue or other plastic repair may be required in persistent problems. Inspection of the foot while the patient is seated includes noting presence of a normal arch, forefoot width, and the presence of calluses and other dermatologic features.

SUPINE EXAMINATION — The examiner can determine the rigidity or softness of the plantar fascia with the patient lying supine. The toes are grasped and dorsiflexed with one hand, while the other hand palpates the plantar aspect of the foot, particularly the bands compressing the plantar fascia. Only by examining many normal feet can the physician become familiar with the pathologic tightly bound plantar fascia. A tear of the plantar fascia should be suspected if the banded fascia is not palpable.

SHOE INSPECTION — Proper shoes should provide support and comfort (proper fit) for the weightbearing foot, with room for the toes to extend fully and to broaden out during weightbearing. Proper fit is determined by having foot size measured while standing. Callus formation at the lateral and medial borders of the metatarsals 1 and 5 suggest too wide a shoe. Palpate the foot in the shoe while the patient stands and note where the tip of the toes lie in the shoe, gaping at the ankle or heel; note heel wear. Improper shoes can cause or exacerbate lower limb disorders, including hallux valgus, hammer toes, hard corns, and plantar keratoses.

How long can a runner run in a pair of shoes before they wear out? A computational finite element analysis (FEA) was made of the stress distribution in the heelpad and a running shoe midsole, using heelpad properties deduced from published force-deflection data, and measured foam properties [16]. Measurements of plantar pressure distribution in running shoes confirmed the FEA. The peak plantar pressure increased on average by 100 percent after 500 km run. Scanning electron microscopy shows that structural damage (wrinkling of faces and some holes) occurred in the foam after 750 km run. Fatigue of the foam reduces heelstrike cushioning, and is a possible cause of running injuries.

Leather soles were meant to be used on wood floors. Newer microcellular foam shock absorbing material used in most exercise and walking shoes is preferred for walking and standing on concrete. The role of shoe sole materials on balance and vertical impact in sports were tested in a randomized, crossover trial of ethyl-vinyl acetate foams of varying thickness [17]. All of the currently available shoes were found to be too soft and thick, suggesting that further improvements in shoes is required.

Shoe modification can be helpful for dorsal exostoses, metatarsalgia, bunions, painful flat feet, and plantar fasciitis. (See "Rehabilitation program for the lower limb").


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