Written by the Thrive Protocol editorial team. Medically reviewed by Dr. Patrick Denard, orthopaedic surgeon, on October 8, 2026

Short answer: Food comes first. Aim for about 1.2 to 1.5 g of protein per kg of body weight each day, since quadriceps strength can drop by roughly 60% in the first month after knee replacement (1). Among supplements, essential amino acids have the most consistent knee replacement trials. Vitamin D is worth testing. Most of the rest is limited or unproven.

This page grades each common supplement by what trials in knee replacement patients (or the closest similar groups) actually found, with study sizes and limits. For food, see What to Eat After Knee Replacement Surgery.

Disclosure: Thrive Protocol sells recovery nutrition products, and some of the nutrients below are in our kits. We say plainly where the evidence is weak, including for ingredients we use.

Why knee replacement changes the supplement question

The new joint is metal and plastic, so most of the healing work happens in the soft tissue and muscle around it. In one study of 20 patients, quadriceps strength fell by 62% about four weeks after surgery, mostly from the muscle not switching on fully and partly from muscle shrinkage (1). Most patients are older, and older adults need more protein to hold on to muscle: the PROT-AGE group recommends 1.2 to 1.5 g/kg per day for older people with acute or chronic illness (2), and a 2024 arthroplasty review cites a goal of 1.2 to 1.9 g/kg (3). For an 80 kg (176 lb) adult, 1.2 to 1.5 g/kg works out to 96 to 120 g of protein a day, or roughly 25 to 30 g at each of four meals and snacks.

Evidence grades at a glance

Grades: Strong = consistent, good trials in knee replacement. Moderate = several trials in knee or hip replacement, some mixed results. Limited = small, indirect or inconsistent. Not supported = no benefit found, or no relevant trials. No option reached Strong.

Supplement Main reason people take it Grade Best evidence in knee replacement
Protein (whey) Meet higher protein needs Moderate 1 RCT, 62 completers, 12 weeks
Essential amino acids / leucine Limit thigh muscle loss Moderate Several RCTs; meta-analysis of 19 studies
Creatine Adjunct for regaining strength Not proven in surgical studies 1 RCT, 37 patients, no benefit
Collagen + vitamin C Connective tissue support Limited No collagen trials found; vitamin C results inconsistent
Vitamin D Correct low levels Limited (test first) 1 RCT, 107 patients, single dose, no difference
Omega-3 (fish oil) General inflammation support Limited No recovery trials in knee replacement found
Curcumin Joint comfort Limited Knee arthritis trials only, low certainty
Magnesium Cover dietary gaps Not supported as a recovery aid No oral trials in knee replacement found
Iron Rebuild blood after surgery Not supported routinely 2 RCTs, no meaningful benefit

Each supplement, graded

1. Protein powder (whey): Moderate

What it is for: reaching your protein target when appetite is low and cooking is hard with a walker.

What studies found: In a randomized trial of 72 knee replacement patients (62 finished), daily whey protein for 12 weeks alongside standard rehab produced greater gains in muscle strength, range of motion and knee scores than placebo (4). A 2025 meta-analysis of 19 studies (903 hip and knee replacement patients) found protein and amino acids reduced muscle loss, but effects on strength were mixed (5). Limits: one single-center whey trial.

Timing: before surgery and through rehab, split across the day.

Safety: ask first if you have kidney disease, since people with severe kidney disease may need to limit protein (2). Whey is dairy.

2. Essential amino acids and leucine: Moderate

What it is for: essential amino acids (EAAs), especially leucine, switch on muscle protein production.

What studies found: In a double-blind trial of 39 adults aged 53 to 76, 20 g of EAAs twice daily from 1 week before to 6 weeks after surgery cut quadriceps volume loss in the operated leg to 8.5%, versus 13.4% with placebo. Strength and function did not differ (6). A Japanese trial randomized 60 patients (52 analyzed) to 9 g of EAAs a day from 1 week before to 2 weeks after surgery; at 2 years, quadriceps strength had recovered to 159% of baseline versus 125% with placebo, though knee scores were similar (7). Limits: small trials, and better muscle numbers did not always mean better function.

How much: a practical target is 3 g of leucine a day, on top of protein-rich meals.

Safety: the 39-patient trial found no differences in kidney or liver blood tests between groups (6).

3. Creatine: Not proven in surgical studies, but can be an adjunct

What it is for: short bursts of muscle energy during strength training.

What studies found: The only knee replacement trial we found randomized 37 adults to creatine (10 g/day for 10 days before, then 5 g/day for 30 days after) or placebo. It found no effect on strength, body composition or function (8). Later in rehab the picture is more hopeful: a meta-analysis of 22 trials (721 older adults, mostly healthy) found creatine plus resistance training added about 1.4 kg of lean mass and modest strength gains versus training alone (9). Limits: that meta-analysis did not include surgical patients.

How much and when: the usual amount is 5 g a day, with no loading phase. If you are later in your recovery and struggling with regaining strength, it is also worthwhile considering. Safety: ask first if you have kidney disease.

4. Collagen with vitamin C: Limited

What it is for: collagen supplies glycine and proline; vitamin C is needed to form collagen.

What studies found: We found no trial of collagen supplements in knee replacement. In 8 healthy young men, 15 g of vitamin C-enriched gelatin before short exercise doubled a blood marker of collagen production (10). In 53 older men with low muscle mass, 15 g/day of collagen peptides plus 12 weeks of resistance training added more lean mass and leg strength than training alone (11). For vitamin C itself, a 2026 review of 10 randomized trials (1,364 knee replacement patients) found inconsistent results for pain, blood loss and recovery, and did not support routine use (12). Limits: indirect, small studies. Collagen is an incomplete protein, so it should not replace whey or food protein.

Timing: no tested schedule after knee replacement.

5. Vitamin D: Limited (test and correct)

What it is for: bone and muscle function.

What studies found: Low vitamin D affects 13 to 63% of joint replacement patients, per a 2026 review (13). But blanket high doses have not shown a clear effect. In a randomized trial of 107 patients, a single 50,000 IU dose on the morning of surgery made no difference to knee function scores or walking test times at 3 or 6 weeks (14). A 2026 systematic review of 11 studies called the evidence inconsistent and insufficient for universal supplementation (15).

Timing: ask for a 25-hydroxyvitamin D blood test at your pre-op visit so any low level can be corrected weeks ahead. Safety: the Institute of Medicine RDA is 600 IU a day up to age 70 and 800 IU from age 71 (16); avoid high doses unless your doctor prescribes them.

6. Omega-3 (fish oil): Limited

What it is for: EPA and DHA support a normal inflammatory response.

What studies found: We found no randomized trial testing fish oil on recovery after knee replacement. On safety, in a heart surgery trial of 1,516 patients, perioperative fish oil did not increase major bleeding compared with placebo (17). Older reviews still list fish oil among supplements with reported bleeding risk (18).

Timing and safety: at the low amount in OptiFuel, there is no need to stop fish oil before surgery. If you take a separate high-dose fish oil, ask your surgeon, and ask before restarting if you are prescribed a blood thinner afterward.

7. Curcumin (turmeric extract): Limited

What it is for: joint comfort.

What studies found: A 2025 network meta-analysis of 17 randomized trials in knee osteoarthritis found turmeric products reduced pain scores versus placebo, with low certainty of evidence (19). That is the arthritic knee, not recovery; we found no trial of curcumin on recovery after knee replacement.

Safety: the NIH says conventional turmeric or curcumin is likely safe for up to 2 to 3 months, but liver injury has been reported with some high-bioavailability formulations (20). The amount in OptiFuel is low, and you do not need to stop it before surgery.

8. Magnesium: Not supported as a recovery aid

What it is for: covering a low dietary intake.

What studies found: Research in joint replacement mostly involves magnesium sulfate given by the anesthesia team, not oral supplements (3). We found no oral magnesium trial on knee replacement recovery.

Safety: the upper limit for magnesium from supplements is 350 mg a day for adults, set because of diarrhea (21). Count every product you take, and check with your doctor if you have kidney disease.

9. Iron: Not supported routinely

What it is for: rebuilding red blood cells.

What studies found: In 72 patients who were anemic after hip or knee replacement, 6 weeks of ferrous sulfate did not change hemoglobin recovery versus placebo (22). In a second trial (120 randomized, 99 completed), iron gave only a small extra rise at 6 weeks, which the authors judged questionable given side effects (23).

Timing and safety: take iron only if blood tests show you need it. Oral iron often causes stomach side effects (23).

Supplement safety before surgery

  • Some supplements, such as garlic and ginkgo, have reported bleeding risks around surgery (18). Your surgeon sets the stop dates for those, and they vary by surgeon and procedure. The fish oil and turmeric in OptiFuel are low-dose, and you do not need to stop them before surgery.
  • Bring a written list of every supplement, with doses, to your pre-op visit, and tell your anesthesiologist too.
  • Ask before restarting any supplement after surgery, especially if you are on a blood thinner.

How Thrive's kits map to this evidence

We checked our product pages and packet labels against the grades above.

Evidence item OptiFuel (in both protocol kits), per packet Recovery and Strength Mix, per scoop
Protein 25 g (whey protein concentrate plus hydrolyzed collagen) None listed
Leucine 3 g 3 g
Other amino acids L-glutamine (amount not listed) Glutamine 2.5 g, arginine 2 g, isoleucine 1.75 g, valine 1.75 g
Creatine Not included Creatine monohydrate 5 g
Vitamin C 500 mg Not listed
Vitamin D 20 mcg (800 IU) Not listed
Magnesium 200 mg (vanilla) to 230 mg (chocolate) Not listed
Omega-3 and curcumin Fish oil powder and MAXICUMA turmeric extract (amounts not listed) Not included
Iron No added iron Not included

In plain terms: the protocol kits are a daily protein and leucine shake with vitamin C, vitamin D and magnesium that helps you meet higher protein needs. They do not contain creatine or iron. Creatine is only in the Recovery and Strength Mix, which fits the later strength phase. Because OptiFuel already provides 200 to 230 mg of magnesium and 800 IU of vitamin D, check with your doctor before stacking extra magnesium or vitamin D on top.

Which product fits where you are

  • Surgery still ahead: Surgical Protocol Kit (OptiFuel plus OptiCharge for the night before surgery). 4-week $299.99, 3-month $499.99, 6-month $669.99. Ideally, everyone on this kit also takes the Recovery and Strength Mix daily.
  • Surgery already done: Recovery Protocol Kit (OptiFuel, no OptiCharge). 4-week $289, 3-month $499, 6-month $669.
  • Rehab and strength phase: Recovery and Strength Mix, $49.99.

Start the Surgical Protocol Kit 1 week before surgery. There is no need to stop OptiFuel before surgery, but share the label with your surgeon before you start, because their instructions come first. Thrive kits are HSA/FSA eligible: you can pay with your HSA or FSA card at checkout or submit the receipt for reimbursement.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Planning ahead? Get the free Surgery Recovery Guide.

Frequently asked questions

What are the best supplements after knee replacement?

Based on current trials, protein and essential amino acids have the most consistent support, mainly for limiting thigh muscle loss. Vitamin D is worth testing and correcting if low. Most other popular options are limited or unproven for recovery.

What vitamins should I take after knee replacement?

There is no proven vitamin stack. Ask for vitamin D and iron blood tests before surgery and correct what is actually low. Vitamin C trials in knee replacement have been inconsistent.

Does collagen help after knee replacement?

We found no collagen trial in knee replacement. Small studies in other groups are encouraging, but collagen should add to complete protein, not replace it.

Is protein powder good after knee replacement?

It can help you reach 1.2 to 1.5 g/kg a day when appetite is poor. One trial found added benefits from 12 weeks of whey with rehab, but protein from food counts toward the same target.

Related reading

References

  1. Mizner RL, et al. Early quadriceps strength loss after total knee arthroplasty. J Bone Joint Surg Am. 2005. PubMed 15866968
  2. Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE). J Am Med Dir Assoc. 2013. PubMed 23867520
  3. Arapovic AE, et al. Nutritional considerations in hip and knee arthroplasty. JBJS Rev. 2024. PubMed 39102471
  4. Li M, et al. Whey protein on muscle mass and functional rehabilitation after total knee arthroplasty. J Back Musculoskelet Rehabil. 2024. PubMed 38820012
  5. Khani Y, et al. Peri-operative protein or amino acid supplementation for total joint arthroplasty: systematic review and meta-analysis. J Orthop Surg Res. 2025. PubMed 40317042
  6. Dreyer HC, et al. Essential amino acid supplementation mitigates muscle atrophy after total knee arthroplasty. JB JS Open Access. 2018. PubMed 30280129
  7. Ueyama H, et al. Perioperative essential amino acid supplementation facilitates quadriceps strength and volume recovery after TKA. J Bone Joint Surg Am. 2023. PubMed 36856692
  8. Roy BD, et al. Creatine monohydrate supplementation does not improve functional recovery after total knee arthroplasty. Arch Phys Med Rehabil. 2005. PubMed 16003653
  9. Chilibeck PD, et al. Creatine supplementation during resistance training in older adults: a meta-analysis. Open Access J Sports Med. 2017. PubMed 29138605
  10. Shaw G, et al. Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr. 2017. PubMed 27852613
  11. Zdzieblik D, et al. Collagen peptide supplementation with resistance training in elderly sarcopenic men. Br J Nutr. 2015. PubMed 26353786
  12. Vosoughi F, et al. Vitamin C supplementation in total knee arthroplasty outcomes: a systematic review of RCTs. Arch Bone Jt Surg. 2026. PubMed 42137519
  13. Siddiqi A, et al. Perioperative nutritional optimization in total joint arthroplasty. J Arthroplasty. 2026. PubMed 41951067
  14. Weintraub MT, et al. Vitamin D3 supplementation prior to total knee arthroplasty: a randomized controlled trial. J Arthroplasty. 2023. PubMed 35988825
  15. Vosoughi F, et al. Effect of vitamin D supplementation on total knee arthroplasty outcomes: a systematic review. Orthop J Sports Med. 2026. PubMed 42212200
  16. Ross AC, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine. J Clin Endocrinol Metab. 2011. PubMed 21118827
  17. Akintoye E, et al. Fish oil and perioperative bleeding. Circ Cardiovasc Qual Outcomes. 2018. PubMed 30571332
  18. Wang CZ, et al. Commonly used dietary supplements on coagulation function during surgery. Medicines (Basel). 2015. PubMed 26949700
  19. Wai HS, et al. Effect of turmeric products on knee osteoarthritis: systematic review and network meta-analysis. BMC Complement Med Ther. 2025. PubMed 40731001
  20. National Center for Complementary and Integrative Health. Turmeric: usefulness and safety. nccih.nih.gov/health/turmeric
  21. Costello R, et al. Call for re-evaluation of the tolerable upper intake level for magnesium supplementation in adults. Adv Nutr. 2023. PubMed 37487817
  22. Sutton PM, et al. Treatment of anaemia after joint replacement: ferrous sulphate versus placebo. J Bone Joint Surg Br. 2004. PubMed 14765861
  23. Mundy GM, et al. The effect of iron supplementation on the level of haemoglobin after lower limb arthroplasty. J Bone Joint Surg Br. 2005. PubMed 15736746

This guide is for education and does not replace advice from your surgeon or care team. Product details checked against mythriveprotocol.com product pages and packet labels on 2 October 2026.