OVER 96% PASS RATE FOR THE NCS, OCS, AND PCS EXAMS › forums › OCS Advantage › Test Question Clarification on Answer
For the following question, both the tibialis anterior and tibialis posterior invert the foot and some may argue that the tibialis anterior is the stronger of the invertors of the ankle. Both muscles are innervated by different nerves. Tibialis posterior is innervated by tibial nerve and tibialis anterior is innervated by deep peroneal N. What is the reasoning behind Tibial N being the correct answer in this case (as opposed to Deep Peroneal N)?
33. Kim is a 60-year-old female who complains of generalized foot and stabbing heel pain. She has always been told she has flat feet, so she has tried many orthotics over the years. Now she feels weakness in the feet and poor balance. She has a history of type 2 diabetes mellitus with two instances of toe ulcerations in the past. She was on intravenous vancomycin for MRSA. She has been walking more recently to lose weight. Manual muscle testing reveals 3+/5 strength in bilateral ankle plantarflexors, 4/5 strength in bilateral ankle dorsiflexors, 3/5 strength in bilateral ankle invertors, and 4/5 strength in bilateral ankle evertors. Kim has obvious flatfoot deformity, which is not flexible. An x-ray performed two days ago showed osteoarthritis in the tibiotalar and talonavicular joints.
You are concerned with her weakness in ankle inversion. Which nerve is responsible for innervating this ankle motion?
A. Deep fibular nerve
B. Superficial fibular nerve
C. Tibial nerve
D. Sural nerve
Natasha, I can definitely see your reasoning on this, however what I was trying to go for in the question was pointing out that the plantar flexors which will be innervated by the tibial nerve are weaker than the dorsiflexors as shown in the manual muscle testing. Also the clinical picture points strongly to posterior tibial tendon dysfunction which would also be innervated by the tibial nerve. When you sit down and take the actual OCS test keep in mind that a lot of the times two answers will seem correct but dive back into the question to see if there’s any evidence to further validate one choice or the other.
Let me know if you have any further questions and happy studies!
Thank you! I started thinking that after I posted this on the forum as well. Especially with the presence of flat foot deformity. That is good advice – I will be sure to do that on the exam – it seems to be the most challenging part for me – Most practice questions I have gotten incorrect, it was between two answers that I had narrowed it down to.
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