Knuckles are the heads of the metatarsal bones. When the hand makes a fist:

Before we discuss the PDF search, let’s review what specific anatomical knowledge you are trying to acquire. A generic free anatomy chart won't help you with these sculpting nuances.

You can view the development history and sample imagery from the original funding campaign on Kickstarter . Where to Purchase

Books like Anatomy for Sculptors by Uldis Zarins are industry standards because they use color-coded 3D renders to show exactly where muscle origins and insertions sit. 💡 Pro-Level Hack

Go to your local public library or university art library. Ask the librarian for an "Inter-library loan" for Anatomy for Sculptors by Uldis Zarins . If they have it, you can check it out for free. Once you have the physical book, you are legally allowed to scan 1-2 pages for personal reference (though not the whole book).

The arm does not move independently of the torso. The clavicle (collarbone) and scapula (shoulder blade) form the shoulder girdle, a floating system that moves continuously to accommodate the rotation of the humerus. When the arm raises above 90 degrees, the scapula rotates upward, shifting the surface masses of the back and shoulder. The Forearm Pivot: Radius and Ulna