The general cost I've seen posted here depending on area seems to range from $1500-4000 depending on whether you're doing one knee or both and if by an orthopedic surgeon or your regular veterinarian.
When I consulted with our local orthopedic surgeon, he gave me the low ($3100) and high ($3800) estimate for the procedure (for both knees as it's a bilateral disease if it was congenital--as it is with us because generally, unless caused by trauma/injury, at this young age, it is a condition inherited from birth). He did say that generally, it costs more to the lower end of the scale, especially in our case, and I think he's the honest type in that regard.
Here is the breakdown (for deepening groove & pinning) in case you're curious as I find the quotes I get for various services are generally similar or more than various parts of the USA as I am located in Canada but in a town sporting a relatively high cost of living compared to most other cities in the country.
Consultation-Surgeon - $160.00
I.V. Catheter Set-Up - 60.00
I.V. Fluids Per Bag - 28.34
I.V. Infusion Pump/Cassette 134.96
Anesthesia Induction - 130.00
Anesthesia Isoflurane/Hour - 253.86 x 2L or 2.5H = 507.72 / 634.65
Anesthesia Monitoring 2 - 270.00
Surgical Prep 2 - 58.34
Patellar Luxation - 690 x 1L or 1.5H = 690 / 1,035.00
Surg. Materials - 25.00 x 8 = 200.00
Surg. Implants - 50.00 x 1L or 2H = 50 / 100
Injection of Medication - 36.24 x 10 = 362.40
RADS-ACCG-Initial 2 Views - 140.00
Estimate of Meds - 50.00
Wards - 1 - 150 x 1L / 2H = 150.00 / 300.00
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Subtotal : 2,991.76 / 3,663.69
Tax : 147.10 / 180.69
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Balance: 3,138.86 / 3,844.38
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When I had inquired about the glucosamine supplements, he did say it will help, but of course, it wouldn't cure the problem. The specialist also voiced his concern regarding arthritis setting in the later we operate as the tissues, cartilege around the joint continues to be worn down with each dislocation/relocation.
With us, we never knew she had the problem until she had gone through a physical exam with one doctor who was just doing the routine exam on her pre-dental work for our first visit with him. However, he did not diagnose her with LP. She just came home displaying symptoms of LP--limping every so often while running and chasing the cat.
This was happening every other day until another vet (breeder's referred one) we took her to for an x-ray examined her. Then it became daily. This was all within a week or half that.
Then with her 3rd vet (had gone to her in the need of a referral to the specialist), after checking the knees, and while waiting for our appointment for the orthopedic specialist to be arranged, she lost all symptoms. No longer limped no matter how hard she played and chased the cat. It went from daily to nothing. I'm not even sure it was slipping and just repositioning itself on its own at that point. It didn't even seem like it was slipping. No clicking noise, nothing. Her vet called it her gentle touch or maybe it was the ortho. who said that. Can't recall. But even after the orthopedic specialist had manipulated her knees to check for himself, she never limped since.
I know it's just a matter of time that she'll need to be operated on. I am hoping for her recovery time to take place during the fall/winter season(s) and then when she's full grown (which she should be now at almost 1.5 yrs). She really is hard on her legs when she's playing without a care in the world. At the first sign of bowleggedness and/or limping, I plan to have her operated on and hopefully, it will be before she's 5 as I'd want her to recover during her "youth" and good overall health.

Since I find myself staring at her hind legs looking for any hint of bowleggedness constantly when she's walking ahead of me, I had recently taken her in for an updated x-ray to monitor the progress of her knees. The results were good. So it helped to ease my mind for now.
If your dog doesn't run, jump, at all athletic, and doesn't show any symptoms--limping, etc, I would think for the time being, supplements should be enough and perhaps some hydrotherapy or other to help strengthen muscles. Personally, if my girl limps, I already think it's gotten far enough to require surgical correction to prevent arthritis, etc, and simply just to allow her to be herself as she LOVES running and playing rough. What I feel now is that I am buying some time because as hard as she is on her legs, even if she wasn't born with the condition, I'd be worried she'd need to be operated on at some point anyway simply from wear and tear.

I don't want to put her through that kind of painful experience more than once as is necessary.
Hope for the best for Uni and her mommy! It is heartbreaking to see them limp while just doing normal daily "dog" stuff.