Well, I have had, once, two versions of the story on my computer. The original one, juste copied from the significant posts (i.e.: without the comments!) and the other (slightly) enhanced (or spoilt!) in a few places, with some fantasies of my own.
Your comment is correct, the one I am posting is the second one.
But I have not kept all the approval posts of your original thread! Sorry...

We arrive at the "knee breaking" (or just tearing) episode...

(...)

But to be suffering at the hands of a woman who’d done that! It made me feel even more powerless, submissive, as the pain increased and I yelled out.

She laughed, and then she relaxed her thighs. She opened her legs, put her hands behind my shoulders and pushed me up into a sitting position. She moved forward so that she was sitting up behind me. She slipped her arms under my armpits and reached her hands back, clasping them behind my neck, breasts pushing against my shoulders. Even without any pressure, my arms were pulled back and my chin was pressed down against my chest.

“This is how you do a Full Nelson. Then you pull down and back like this”

She applied just enough force to demonstrate the move properly. It hurt. I could see how it could hurt a lot more. Then she took the pressure off but still kept the hold.

“And you can always do a Bodyscissors as well, from this position”

She raised her legs, wrapped them around my waist and briefly applied the holds simultaneously to demonstrate their effect. I couldn’t breathe.

She let me go and clambered off the bed. Jill eagerly took her place, easily overcoming my resistance, and soon had me in position. She was strong and I was weakened anyway. Once again, a feeling of total vulnerability overcame me.

She took a deep breath, breasts pushing against my back, and began applying the holds with some force. I tried to cry out but my throat was being crushed down, my shoulders were being stretched back and Jill’s lean legs were biting into my torso, squeezing the air out of me.

She relaxed momentarily, took another breath, and piled on the pressure again.

Eve took my left ankle in one hand, slipping the other arm behind my knee and pulling it up. Then she pressed my ankle down.

My knee felt like it was being torn apart.

Jill’s legs squeezed together harder, crushing my sides. Her strong arms ****** my chin against my chest, choking me. Eve worked on my knee. Tears of pain ran down my cheeks.

Eventually, they released me.

“How much longer have we got, Jill?”

She consulted the clock.

“We’ve gone over ten minutes, Eve. Maybe it’s time for another throw of the dice? It’s your turn now!”

Eve picked up the dice and rolled it…
She grinned.

“Look! It’s a five again!”

She grabbed a wrist and an ankle and pulled me to the floor. The fall winded me. It hurt my back.

She let go of my wrist and moved between my legs. She crouched down and pulled them up, trapping my ankles beneath her shoulders, her arms linked under my thighs. She stood up and flipped me over so that my face was to the carpet, and lowered herself onto my back, her arms pulling on my legs.

She settled her weight more firmly on me. I cried out as my ribcage was crushed into the floor as she hauled back on my legs. My knees felt like they’d pop.

“Hey Jill! You’ve got a perfect shot there!”

“Hmmmm?”

“Why don’t you kick his balls, Jill!”

I tried to cry out, but I had no breath.

Eve pulled back further.

Jill kicked and stomped my balls and cock as Eve held me exposed. Her hard boots crashed into me again and again.
Eve let go of my legs and climbed off me. I tried to turn onto my side, but my spine felt like it was cracked. My balls were throbbing sickeningly and my groin area felt battered and bruised. I just lay there, waiting for the agony to subside.

I opened my eyes and groaned. My two torturers were standing over me, towering up in their boots. They were grinning with sadistic delight.

“I bet your back’s a bit sore now isn’t it, baby? And your balls!”

They laughed.

“And I bet your legs hurt, as well, don’t they baby?” Eve purred.

My hands flinched to my left leg; Eve’s quick eyes noticed a weakness to exploit. I immediately regretted being so obvious.
I was still lying face down on the carpet. Eve quickly placed her booted foot on the back of my left knee. She trod down and I cried in pain. The bones and sinews of my joint were crushed under her weight. I felt my kneecap being ****** to one side. Then she lifted her foot, stood back a little, and then dropped her knee down into the same spot, making sure she landed with all her weight. I screamed into the carpet.

Then she leaned over, grinding my knee against the floor, and grabbed my left ankle. She pulled it up, tearing my knee-joint against the bulk of her own heavy knee, and leaned back.

My screams grew more desperate. I felt as though my knee was about to tear apart. Something popped with a blinding spear of pain. Eve laughed and relaxed the pressure, still holding my ankle. I lay sobbing and groaning, the carpet under me wet with my tears.

“Jill, while I’ve got him here, why don’t you stand on his balls?”

There was a pause.

I tried to bring my legs together, but my movements were weak. Jill’s boot easily ****** my legs apart as she stepped between them. She began probing my slippery ball-sack, but couldn’t get a proper purchase. My scrotum was tight with fear. Nevertheless, her forceful prodding intensified the ache in my balls.

“Why don’t you tie them up with the belt?” suggested Eve in a tone both practical and diabolical. She pulled back on my leg while Jill got the belt
Jill ****** herself between my legs and tied the belt around my balls. Then she stood up and tried to catch them beneath her boot. Despite the pain in my spine I tried to lift my balls off the carpet, but Eve leaned down on the small of my back, pressing my pelvis to the floor.

Jill’s foot finally found my balls and she began putting her weight on them, pinning me down. I began screaming into the carpet again.

Eve took her hand off my back and grabbed my ankle in both hands. She began twisting and pulling at my leg, ******* it back against her heavy, solid knee. The cartilage, or whatever she’d popped before, ripped with pain. The combined agonies of my leg and balls tore my breath away.

They laughed at my distress and carried on torturing me, making the pain surge and ebb, keeping me from passing out to avoid it.

“Whose go is it next, Jill?”

“I think it’s mine, actually!”

“Are you ready for your turn now?” She relaxed her grip in my ankle.

“I suppose so…but I’m enjoying this!” She stepped hard onto my balls and held her whole weight there.

They laughed.

It felt as though a giant hand was clutching at my guts. My balls were bursting in torment. My back screamed in pain. Eve was still kneeling heavily on my torn knee.

Then Jill stepped off. A moment later, Eve raised herself from my leg. I lay paralysed with pain, as the crashing waves gradually began to subside.

They waited patiently.

Eventually I was able to move, groaning as I managed to turn myself on my side. I paused to regain my breath against the stabs and currents of pain. Then I eased myself over onto my back, trying to settle with the least discomfort, and tried a couple of deep and painful breaths. I opened my tear-filled eyes.

They were watching me with sensually sadistic interest. They were enjoying my pain. And they were going to give me more.
“You ready for some more?” Jill picked up the dice and rolled it before I could speak.

“And it’s…it’s another Five! You poor thing! It says…both wrestle with you - no holds barred - for ten minutes, or wank you off. Shall we wank you off now, sweetie? Or do you want to wrestle us a bit more?”

I struggled to reply.

Eve responded.

“Let’s wank him off. Get that bit over with. His balls will hurt more afterwards. They’re much more sensitive just after they’ve come”

Jill looked at her friend with fascination. “How do you know that?”

“Well…you know…you pick these things up, don’t you? It might have been that Mandy from the gym. You know she works as a dominatrix? Gets paid for having fun! I mentioned what I’d been up to – mentioning no names – and she said we could use her dungeon next weekend. She’s got all sorts of torture devices in there. It'll be great!”
“Mandy?”

“Yeah, Mandy!”

“Mandy’s not a…dominatrix?!!”

Eve nodded, smiling.

“No! But she’s so…sweet! She wouldn’t hurt a fly!”

Eve laughed. “No, she probably wouldn’t! But she definitely likes hurting men. And she said it hurts them much more after they’ve…you know…come”

“And sweet Mandy said we can use her place next weekend? Use her…torture stuff?”

“Yeah!” Eve replied, excited. “Sweet Mandy! She said she’d show us how to use the stuff”

“She’ll show us? She wants to be there as well?”

“Oh yeah! But only if you want her to be. She’ll let us use it anyway. I think she might want me to…join her in her dungeon sometimes. She’s always looking at me, you know? Maybe she wants to see if I’d like that torture-chamber stuff”

They laughed.

“OK…” Jill looked down at me. “I’ll think about it. While I’m wanking him off. Let’s tie him to the bed again. I’ll wank him really slowly and make him writhe and squirm for it, make you bend and twist and thrash about while I tease you, sweetie! I wonder how your poor back’ll take it…”

They manhandled me up from the floor and pushed me onto the bed. Every movement hurt me. They weren’t being gentle. They tied me down again. Despite the pain and the fear of the pain to come, one thought anchored me - Jill was going to make me come! It wasn’t a tease this time; they wanted me to come just so they could hurt my balls even more.

“Are you ready, sweetie?” Jill asked, taking my still hard cock in her hand.
“Well it certainly feels like you are!”

They laughed.

She began pumping my cock, firmly and steadily. Knowing for sure that the orgasm beginning to build was at last going to be satisfied, I relaxed and began moaning with pleasure. She slowed down a little, but this seemed to increase the sensation and the orgasm welled up, unstoppable. She took her hand away and sat back, grinning.

My body convulsed as I teetered on the brink, but the sudden stabbing and searing pains in my back and my leg hauled me back.

They laughed again, delighting in their cruelty.

“Was that nice sweetie? Did I make you feel like coming?”

“God…yes! But please…are you going to let me…let me…come?” I pleaded.

“You really want me to make you come now?”

“Please Jill! Please make me come. You turn me on so much!”

“OK, you smooth-talking bastard!” she laughed at me. I smiled back. A flicker of our normal relationship flashed in her eyes, but then the look of sadistic enjoyment returned.

She gently held my penis again. It throbbed in her fingers.

“So are you up for a session at Mandy’s next weekend, then?” she toyed with my stretching penis.

I gulped. “I…er…yes...ok”

“Good! I’ve not quite made my own mind up about it yet. Maybe I don’t want to share my little pain-slut around too much…”

Her remark brought a small but welcome sense of relief that Jill still had some idea of boundaries.

“Right then, Eve…shall we try our little experiment? See if Mandy’s right?”

“OK! What do you want me to do?”

“Why don’t you get his balls in a good hard squeeze and I’ll make him come? If you keep squeezing after he’s come, we can see if it hurts more afterwards, can’t we?”

Any sense of relief vanished.

Eve grinned, sat on the bed, and cupped my balls in one strong hand.

“How hard should I squeeze them, Jill?”

Jill’s hand wrapped around my cock and began pumping it again.

“As hard as you like!” She smiled down at me.

Eve’s hand closed like a vice on my balls.
I screamed as Eve increased the pressure.

Jill continued to work on my cock. Then she took her hand away and lowered her head. She took my aching cock into her hot mouth.

Despite Eve’s sickening grip, Jill soon made me come. My orgasm was tremendous, but Eve’s hold on my balls disrupted any feelings of pleasure. In fact, my balls hurt more with every spurt. Jill carried on sucking me, swallowing, as my ejaculations slowly decreased and my agonised body thrashed in its bonds. As the orgasm spent itself, after seven powerful spurts, the pain in my emptied balls became truly unbearable.

Jill took her hot mouth off my penis, licking her lips, and studied my reaction with sadistic amusement.

“Looks like Mandy was right, Eve! Are you squeezing him harder now?”

Eve grinned at her.

“No…I’m not squeezing any harder. But it does look like it is hurting him more, much more, doesn’t it?

I began begging for her to stop. The unrelenting ball-pain was sending nauseous waves of agony crashing through my body. She kept the pressure on for a while and then relaxed her grip, satisfied. Then she had a thought...

(to be continued...)