24: Limb Length Discrepancies - Smith

Question 1

what is a significant LLD?

Answer 1

3mm - 22mm

the numerical value is not as important, significant means it causes symptoms

Question 2

structural v. functional LLD

Answer 2

structural - anatomical shortening [polio, physeal damage, congenital dysplasia, post surg]

functional - due to biomechanics [excessive STJ pronation/greater than 3 degree eversion* when compared to contralateral limb, joint contracture, axial malalignment, shoegear induced]

could also be a combination

Question 3

pelvis tilts downward on ____ side

Answer 3

short

this is a structural LLD compensation

Question 4

scoliosis with convex side over _______ limb

Answer 4

short
(reducible with NWB - can become rigid)

this is a structural LLD compensation

Question 5

symptoms association with LLD

Answer 5

• asymptomatic
• pain with standing and WB
• sacroiliac jt pain due to pelvic tilt [pelvic tilt syndrome]
• lateral knee pain on short limb, medial knee pain on long limb
• low back pain due to disc protrusion with scoliosis

Question 6

pronate on long side, supinate on short side

Answer 6

structural LLD

Question 7

knee pain laterally on one knee and medial on the other indicates …

Answer 7

lateral on short limb

medial on long limb

Question 8

pronation is …

Answer 8

compensation for structural LLD or a cause of a functional LLD

Question 9

how to do a direct clinical measurement?

Answer 9

ASIS to medial malleolus (could also be ASIS to lateral malleolus or umbilicus to medial malleolus)

watch out - obese pts, jt contracture not accounted for, torsion of bones not accounted for, pelvic torsion not accounted for

Question 10

pt has WB LLD, but does not have NWB

Answer 10

probably functional

Question 11

how to do an indirect LLD check?

Answer 11

• WB with foot in resting calcaneal stance position
• Pelvic landmarks palpated, keeping hands parallel
• ASIS and PSIS located
• Blocks of a known thickness placed under short side until landmarks are at same level
• Pelvic height difference not accounted for
• Third reference point added for accuracy
  [Greater Trochanter - If this measurement is equal then the LLD occurs within pelvis]

Question 12

pelvic compensation (long v short limb)

Answer 12

Posterior pelvic rotation with pronation on long limb

Anterior pelvic rotation with supination on short limb

Question 13

most common compensation

Answer 13

functional scoliosis

Must determine if scoliosis is functional and a result of a LLD or if is the primary pathology and the LLD is a compensation for the scoliosis

Question 14

fixed scoliosis

Answer 14

does not reduce with NWB

Question 15

If functional caused by increased pronation, must correct with …

Answer 15

orthosis

If structural then a lift is used
If combined, then an orthotic with a lift

Question 16

how do you use a lift?

Answer 16

If discrepancy 1 cm or more, a full length lift is used to prevent equinus

Increase in increments of 3mm (1/8”) per week

Can get 8 mm of lift in a normal shoe

If greater than 8 mm needed, apply 50% of lift to shoe of short side and acquire other 50% by deepening shoe on long side