with one's knuckles
knuckles 表示“指节”时常用复数，并与物主代词连用，如 one's knuckles。
She tapped on the glass with her knuckles.
她用指关节敲了敲玻璃。
握拳时手指的关节；蹄爪；膝关节
Any of the joints between the bones of the fingers.
握拳时手指的关节
a joint of a finger when the fist is closed
A mechanical joint.
The curved part of the cushion at the entrance to the pockets on a cue sports table.
The kneejoint of a quadruped, especially of a calf; formerly, the kneejoint of a human being.
A cut of meat of various kinds.
A convex portion of a vessel's figure where a sudden change of shape occurs, as in a canal boat, where a nearly vertical side joins a nearly flat bottom.
A contrivance, usually of brass or iron, and furnished with points, worn to protect the hand, to add force to a blow, and to disfigure the person struck; a knuckle duster.
The rounded point where a flat changes to a slope on a piste.
He knocked twice on the table with his knuckles to get everyone's attention.
他用指节在桌上敲了两下，以引起大家的注意。
用法提示：knuckles 是名词复数形式，表示指节。
Her knuckles turned white as she gripped the steering wheel.
她紧握方向盘时，指节都变白了。
用法提示：knuckles 在本句中作主语，是名词复数，表示指节。
I grazed my knuckles on the rough wall while moving the sofa.
我搬沙发时，指节蹭到了粗糙的墙壁上。
用法提示：knuckles 作宾语，是名词复数，表示指节。
knuckles 表示“指节”时常用复数，并与物主代词连用，如 one's knuckles。
She tapped on the glass with her knuckles.
她用指关节敲了敲玻璃。
动词 knuckle 表示“用指节击打”，直接接击打的对象。
He knuckled the table in frustration.
他沮丧地用指节敲打桌子。
若要说明具体击打部位，可在宾语后用 on/in 接身体部位。
She knuckled him on the back.
她用指关节敲他的背。
含义比 knuckle 宽泛，可指各种关节；仅当上下文明确是手指时才可换用，口语中 knuckle 更自然。
较正式或解剖性的说法，语义明确；日常口语的惯用搭配中通常仍用 knuckle。
grammar · medium
易错句子She has strong knuckle.
正确表达She has strong knuckles.
knuckle 是可数名词，指多个指关节时应用复数 knuckles；中文名词没有复数变化，容易漏加 -s。
grammar · medium
易错句子The teacher hit him in the knuckles with a ruler.
正确表达The teacher hit him on the knuckles with a ruler.
表示击打身体某一部位（表面）时，介词用 on，不用 in；因此是 hit him on the knuckles。
grammar · medium
易错句子She knuckled on the door and waited.
正确表达She knocked on the door and waited.
knuckle 作动词不是“敲门”；“敲门”应用 knock on the door。不要因拼写相近而混淆。
knuckle（指节）特指手指上握拳时突起的关节；joint（关节）是泛指，身体任何两骨相连处都叫 joint。若想明确指“指节”，用 knuckle，而不用 joint。
擦伤指节
He scraped his knuckles while fixing the engine.
他修发动机时擦伤了指节。
因紧张而发白的指节
She watched the horror movie with white knuckles.
她看恐怖片时紧张得指节发白。
批评；训斥
The school gave him a rap on the knuckles for cheating.
学校因他作弊而训斥了他。
赤手空拳；不戴拳套的拳头
In the street fight, he used bare knuckles.
在那场街头斗殴中，他赤手空拳。
指关节
His knuckle joint was swollen after the punch.
那一拳之后他的指关节肿了。
开始认真工作/努力用功
If you want to pass the exam, you'd better knuckle down and study.
如果你想通过考试，最好开始认真用功学习。
屈服，让步，认输
The workers refused to knuckle under to the manager's threats.
工人们拒绝屈服于经理的威胁。
令人紧张得攥紧拳头的；惊险刺激的
The helicopter ride through the storm was a white-knuckle experience.
乘直升机穿越暴风是一次令人紧张得攥紧拳头的经历。
Dictionary facts from ECDICT, WIKTIONARY.