• WordNet 3.6
    • n kneepan a small flat triangular bone in front of the knee that protects the knee joint
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Webster's Revised Unabridged Dictionary
    • n Kneepan (Anat) A roundish, flattened, sesamoid bone in the tendon in front of the knee joint; the patella; the kneecap.
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Century Dictionary and Cyclopedia
    • n kneepan The kneecap or patella.
    • n kneepan In entomology, the femoral concavity into which the tibia is inserted.
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In literature:

Fauchelevent had dislocated his kneepan in his fall.
"Les Misérables Complete in Five Volumes" by Victor Hugo
The swelling is seen especially below the kneepan, on each side of the front of the joint, and also often above the kneepan.
"The Home Medical Library, Volume I (of VI)" by Various
Step, now, or I'll crack open yer kneepans, ye robin's egg.
"Red Men and White" by Owen Wister
It most frequently occurs in the stifle joint, where dislocation of the kneepan (patella) takes place.
"Special Report on Diseases of Cattle" by U.S. Department of Agriculture