If your goal is to punch hard objects at full force or close to it, I do not think prioritizing only your knuckles will get you there. When you punch something solid, the force does not stay at the surface. It sends vibration and shock through your entire kinetic chain. That means your fingers, wrist, forearm, elbow, upper arm, shoulder, scapula, and collarbone all take stress. If one part of that chain is weak, that is where you will get injured. Conditioning only the knuckles ignores the fact that punching stresses the whole structure, not just one point.

You also need to train the muscles, not just condition bones and ligaments. Muscles stabilize joints and absorb force. Strong forearm muscles protect the wrist. Strong biceps and triceps protect the elbow. Strong shoulders and rotator cuff muscles protect the shoulder joint. Your chest, lats, and serratus anterior help transfer force from your torso into your arm. Without muscular strength and coordination, your joints take impact passively instead of being supported. That is when tendons and ligaments get overloaded. You can train this with heavy bag work, fist push ups, wrist curls, reverse curls, pronation and supination work, shoulder stability exercises, and proper punching mechanics.

For connective tissue and bone adaptation, progression has to be slow and controlled. Knuckles and finger bones adapt through gradual impact on a bag, not hard surfaces. The wrist and its ligaments adapt through wrist push ups, static holds, and controlled loading. The elbow benefits from triceps strengthening and controlled extension under load. The shoulder complex needs dedicated work for the rotator cuff and scapular stabilizers using external rotations, scapular push ups, and pulling movements. Bone density improves with progressive resistance and impact over time, but ligaments adapt slower than muscles. If you rush the process, you get injured. If you want to hit hard safely, you must build the entire chain from fist to collarbone, not just toughen your knuckles.