cornuate navicular and the posterior tibial tendon

Perhaps my navicular is too long a curves back towards the rear foot too much. I've read that the PT is like a lever using the medial malleolus as the fulcrum. The problem is that some of us may have a shorter lever, a shorter distance between the PT Tendon insertion into the navicular bone and medial malleolus.

Perhaps this shorter lever explains my muscular calves. The inefficent PT setup requires more muscle to lift the rear foot from the ground.

An image from the MRI, bisection of ankle, view as if from behind me standing:



This could be the source of my problems. The radiologist describes this as "suggestive of a Type III os naviculare". This is an enlarged "medial horn" of the navicular bone (red arrow). The presence of a navicular type 2 or type 3 is a risk factor for posterior tibial tendon problems, as it "leads to a more proximal insertion of the PTT". Thus, "the leverage of the malleolus on the PTT is reduced and therefore the stress on the tendon increases."

http://www.rbrs.org/dbfiles/journalarticle_0220.pdf
http://www.ajronline.org/cgi/content/full/175/3/627