Posted by Dr. Aamir Ahmad, MD
on November 01, 2026
Written by Dr. Aamir Ahmad, MD — Orthopedic Sports Medicine Surgeon
Key Takeaways
- Protein is the priority. After knee replacement, aim for roughly 1.2 to 1.5 g of protein per kilogram of body weight per day, spread across 3 to 4 meals, unless your doctor gives you a different target.
- Your thigh muscle shrinks fast after surgery. Essential amino acids taken before and after knee replacement reduced that muscle loss in a randomized trial.
- Fiber and fluids prevent the most common early complaint. Constipation from pain medication and reduced movement affects most patients in the first weeks.
- Check vitamin D and iron. Low vitamin D and anemia are both linked to worse outcomes after joint replacement, and both can be corrected.
- Eat for physical therapy. A protein-rich snack before PT gives your muscles what they need to rebuild.
Why nutrition matters after knee replacement
A total knee replacement is a major operation for your body, not just your knee. In the weeks afterward, three things work against you at once: your body is repairing bone and soft tissue, you're moving far less than usual, and your appetite is often poor because of pain medication and fatigue.
The result is rapid loss of quadriceps (front-of-thigh) muscle, which is exactly the muscle you need to walk, climb stairs and get through physical therapy. In a randomized trial of knee replacement patients, the placebo group lost 13.4% of quadriceps muscle volume in the operated leg within six weeks, compared with 8.5% in the group taking essential amino acids.
Nutrition before surgery matters too. Patients with low blood albumin, a marker of poor nutrition, have higher rates of complications and readmission after joint replacement.
How much protein do you need?
For healthy older adults, the PROT-AGE expert group recommends 1.0 to 1.2 g of protein per kilogram of body weight per day, and 1.2 to 1.5 g/kg for people recovering from acute illness or injury. Surgery falls into that second group.
| Body weight | Daily protein at 1.2 g/kg | Daily protein at 1.5 g/kg |
|---|---|---|
| 130 lb (59 kg) | 71 g | 89 g |
| 160 lb (73 kg) | 87 g | 109 g |
| 190 lb (86 kg) | 104 g | 129 g |
| 220 lb (100 kg) | 120 g | 150 g |
If you have kidney disease, ask your doctor before increasing protein. For a deeper look, see our guide to protein after surgery.
Spreading protein out works better than one large serving. Aim for about 25 to 40 g at each meal. Foods high in leucine, an amino acid that switches on muscle building, are especially useful: eggs, dairy, whey, fish, chicken and lean meat.
What to eat, week by week
The first few days (hospital and home)
Appetite is usually at its lowest. Don't worry about perfect meals. Focus on getting protein and fluids in, in whatever form you can manage.
- Greek yogurt, cottage cheese, eggs, soups with chicken or lentils
- Protein shakes or smoothies if solid food is hard
- Water, broth and diluted juice to stay hydrated
- Small, frequent meals instead of three large ones
Weeks 1 to 2: prevent constipation, keep protein up
Opioid pain medication slows your gut. In a study of orthopedic surgery patients prescribed opioids, 69% reported constipation symptoms two weeks after surgery. Being less mobile makes it worse.
- Fiber: oats, berries, pears, prunes, beans, lentils, vegetables, whole grains
- Fluids: drink regularly through the day, unless you've been told to limit fluids
- Movement: short walks as your PT allows help your gut as well as your knee
- Ask your care team about a stool softener if you're on opioids. Many surgeons prescribe one routinely.
Weeks 2 to 6: fuel physical therapy
This is when your muscles are being asked to work hardest. Time protein around PT sessions.
- Have a protein-rich snack 30 to 60 minutes before PT: yogurt with fruit, a shake, or eggs on toast
- Eat a meal with protein within a couple of hours after PT
- Include vitamin C-rich foods (citrus, kiwi, peppers, strawberries, broccoli), which your body needs to build collagen in healing tissue
- Keep eating enough overall. Recovery isn't the time for a strict diet, even if weight loss is a long-term goal
After 6 weeks: rebuild
Most people are moving much more by now. Keep protein high while you rebuild strength, and work toward a long-term eating pattern that supports a healthy weight, since extra body weight adds load to your new knee.
Key nutrients to discuss with your surgeon
Vitamin D
In a meta-analysis of 9,895 hip and knee replacement patients, about 53% had insufficient vitamin D and 39% were deficient, and low vitamin D was associated with higher complication rates. A 2026 systematic review found vitamin D supplementation in knee replacement patients was linked to lower complication and joint infection rates, though the authors note the evidence is still limited. Ask for a blood test before surgery if you haven't had one.
Iron
About 22% of joint replacement patients are anemic before surgery, and the rate is higher in knee replacement. In anemic patients, iron treatment before surgery reduced blood transfusions. Iron-rich foods include red meat, beans, lentils, spinach and fortified cereals. Only take iron supplements if a blood test shows you need them.
Essential amino acids
In the Dreyer trial, patients took 20 g of essential amino acids twice daily for 7 days before and 6 weeks after knee replacement. A systematic review of randomized trials concluded that amino acid supplementation after knee replacement reduces muscle atrophy and leads to better strength and function than placebo.
Foods to limit
- Alcohol: it interacts with pain medication and blood thinners, disrupts sleep and can impair healing.
- Very salty, ultra-processed foods: they can worsen swelling and fluid retention.
- Large amounts of vitamin K-rich greens if you take warfarin: you don't need to avoid them, but keep your intake consistent and follow your doctor's advice. Newer blood thinners don't have this issue.
- Herbal supplements: some affect bleeding. Check our list of supplements to stop before surgery and ask before restarting them.
Sample day of eating after knee replacement
| Meal | Example | Approx. protein |
|---|---|---|
| Breakfast | 2 eggs, whole-grain toast, berries | 15 g |
| Pre-PT snack | Greek yogurt (200 g) with kiwi | 20 g |
| Lunch | Lentil soup with chicken, side salad | 30 g |
| Afternoon | Recovery shake | 20 g |
| Dinner | Salmon, potatoes, broccoli | 30 g |
| Evening | Cottage cheese with pear | 12 g |
| Total | ~127 g | |
Where OVIAL fits
Many patients find it hard to reach their protein target with food alone, especially in the first two weeks. The OVIAL Surgical Nutrition Kit covers the 2 weeks before and 4 weeks after surgery, with essential amino acids, whey protein isolate, collagen peptides, vitamin D and vitamin C. Our knee replacement recovery guide explains how each phase lines up with your rehab.
Frequently asked questions
What is the best thing to eat after knee replacement surgery?
There isn't one best food. Protein-rich foods at every meal (eggs, dairy, fish, poultry, beans), plenty of fiber and fluids, and vitamin C-rich fruit and vegetables cover the most important needs.
Should I take a protein shake after knee replacement?
If you can't reach your protein target with food, a shake is an easy way to close the gap, especially when your appetite is low. Choose one without herbal blends and check with your surgeon.
Why am I not hungry after knee replacement?
Anesthesia, pain medication, constipation and reduced activity all lower appetite. It usually improves within a couple of weeks. Small, frequent, protein-rich meals help in the meantime.
Does diet affect swelling after knee replacement?
Diet won't replace ice, elevation and PT, but limiting very salty foods and alcohol, and staying hydrated, can help.
This article is for general education and isn't a substitute for advice from your surgeon, physician or dietitian. If you have diabetes, kidney disease or take blood thinners, ask your care team before changing your diet or adding supplements. OVIAL products are not intended to diagnose, treat, cure or prevent any disease.
References
- Dreyer HC, et al. Essential amino acid supplementation mitigates muscle atrophy after total knee arthroplasty: a randomized, double-blind, placebo-controlled trial. JBJS Open Access. 2018.
- Effects of amino acid supplementation on muscle mass, muscle performance and functional capacity in subjects undergoing total knee arthroplasty: a systematic review of randomized clinical trials. Eur J Orthop Surg Traumatol. 2024.
- Age-related muscle anabolic resistance: inevitable or preventable? Nutr Rev. 2023 (summarizing PROT-AGE recommendations).
- Hypoalbuminemia remains an independent predictor of complications following total joint arthroplasty.
- Ortega G, et al. Opioid-induced constipation and associated symptoms after orthopedic trauma. Pain Manag Nurs. 2024.
- Emara AK, et al. Hypovitaminosis D in lower extremity joint arthroplasty: a systematic review and meta-analysis. J Orthop. 2020.
- Vosoughi F, et al. Effect of vitamin D supplementation on total knee arthroplasty outcomes: a systematic review. Orthop J Sports Med. 2026.
- Impact of preoperative anemia on patients undergoing total joint arthroplasty.
- Preoperative iron treatment in anaemic patients undergoing elective total hip or knee arthroplasty: a systematic review and meta-analysis. BMJ Open. 2020.
