This was taken of a thread at AF. The author is Killer and I hope he doesn't mind me reposting this:
Feet Flatten (pronate) and externally rotate (turn out): May indicate tightness in soleus, gastrocnemius, peroneals, hamstring and piriformis and/or weakness in gluteus medius.
Knees buckle inward: May indicate weak/inhibited gluteus maximus/medius, tight adductors and iliotibial band (IT band).
Low back arches: May indicate tight iliopsoas and/or other hip flexors and latissimus dorsi, compensating for a weak core.
Low back rounds: May indicate overactive external obliques, compensating for a weak core.
Arms fall forward: May indicate tight latissimus dorsi and/or pectoralis major/minor and weak lower trapezius, rhomboids, teres minor and infraspinatus.
Cervical spine: If it hyperextends, this may indicate overactive sternocleidomastoid and weak stabilizers.
So this is supporting that knees going inward are weak abductors
I stand corrected folks. Thank you for the replies to this thread.