Monday, May 2, 2016
Podiatrist's Biomechanics Corner: Email Advice
Hi Dr Blake,
I had a patient present today with some mild back pain, right foot pain, previous history of anterior right knee pain. No symptoms on the left side at all. He enjoys hiking and running.
Dr Blake's comment: As you begin to sort out the historical clues, you often see patterns of dominance to one side or the other. Since there are many reasons for this syndrome, all we can say now is that he has a more injury prone right side.
No history of trauma and no medical conditions.
Dr Blake's comment: With no history of trauma, the biomechanical assessment of the patient will probably play a big part of his pain syndrome, likely related to overuse. When you overuse your body, the weakest links in the chain (called biomechanical faults) start to complain first.
Based on these unilateral symptoms, I wanted to check if there was a limb length discrepancy. The iliac crests and greater trochanters were level, and the block test felt unstable on him for both the right and left foot at 3mm thickness.
On gait examination, there was slight right shoulder drop, left arm further away from body, both hips were slightly externally rotated, more tibial varum on the right compared to left, right foot supinated and left foot neutral.
Dr Blake's comment: The right shoulder drop can be just the rounding of the shoulders. I like to look at the finger tips also to see if the lower shoulder is on the same side as the lower finger tips. A true shoulder drop can signify a short leg, a shoulder or neck injury (no history here), or a scoliosis. The whole trunk can be pulled to the side of the shoulder drop which is called limb dominance. The opposite arm can be further away from the body to equalize the fall to the limb dominant side. The external hip position is of unknown significance now, and the greater tibial varum generally leads to a greater supinated position (in this case on the right).
RCSP was 4 degree inverted for right and neutral for left. Supination resistance was low for right and moderate force for left. Jack's test was low for right and moderate to hard force for left.
Dr Blake's comment: So, we have an inverted foot on the right and moderately pronated foot on the left. In classic biomechanics, you can assume that the short foot is the right and longer, more pronated foot, is the left.
My diagnosis was possible sciatica, 3rd MPJ plantar plate sprain / capsulitis on right and non painful functional hallux limitus on left. Could not reproduce the symptoms of his right knee pain and there was no joint crepitus or limited knee ROM.
Dr Blake's comment:Excessive supination on the right side is a irriation to the low back causing tightness in the hamstrings as the knees straighten. The anterior knee pain may be medial meniscal compression syndrome due to the varus thrust at the knee from the rearfoot supination, or just a pinching of the anterior synovium from knee extension. The excessive inversion of the foot would place pushoff more lateral off the first/second rays and onto the weaker 3rd ray.
Based on my assessment and diagnosis, I feel that the LLD is functional instead of structural and am thinking of using orthotic therapy instead of full length heel lifts.
Dr Blake's comment: With level Iliac Crests, and Greater Trochanters, negative block test, unless you get a Standing AP Pelvic Xray in Normal Stance, functional LLD makes sense. Functional LLD means the right side is functioning asymmetric to the left. And it sure is!! But the compensation for a structurally long left leg, with excessive supination on the right and excessive pronation on the left can present like this. Keep a Plan B!
For the orthotic design, I was thinking of reducing the supination on his right foot using a Root balanced orthotic, lateral Kirby skive, lateral arch fill and leaving the anterior edge of the orthotic to full thickness so that the force is transferred away from the forefoot and towards the midfoot / arch area.
Dr Blake's comment: So we are on the same page, when you want more lateral support, you tell the lab to have less lateral arch fill. I have not done the part of leaving the anterior edge thick (like a met bar), but makes sense. I would typically skive out more met arch in the plaster before pressing to get more met arch (maybe the same??). See the video below and make sure he can get to vertical on the right to know where to balance the heel to.
For the left foot, I plan to reduce the pronation through a Root balanced orthotic and reduce the functional hallux limitus by adding a reverse Morton's extension.
Since his left foot and leg is asymptomatic, I AM not sure if I should I add a medial Kirby skive, increase the width of the orthosis and reduce the medial arch fill to minimum? I do not want to cause any new symptoms for his left foot.
Dr Blake's comment: I think your approach is fine on the left, although the moderate Jack's test may need alittle more inversion. I love to place in the heel this inversion force, so a medial Kirby or 15 degree inverted pour would work subtly.
Thanks for reading and your thoughts on this are greatly appreciated.