What Is Malnutrition?
Malnutrition isn’t just about being underweight. It includes poor intake or absorption of calories, protein, vitamins, or minerals. Even patients with a “normal” or high BMI can be malnourished. In fact, many individuals (especially in the United States) are considered to be well-fed but undernourished, meaning they consume enough calories but still lack the key nutrients (micro and/or macro) their body needs to function and heal properly.
How Common Is Malnutrition in Joint Replacement Patients?
- A study of patients ≥65 years old undergoing elective total hip arthroplasty (THA) found 38.4% were malnourished pre‑operatively.
- In another study of 220 elderly THA patients, about 12.3% had protein‑energy malnutrition (PEM).
- Literature reviews show variable prevalence depending on screening method, but malnutrition is far from rare in hip/knee replacement populations.
What the Data Says: Worse Outcomes When Nutrition Is Poor
Malnutrition before hip or knee replacement has been associated with:
| Outcome | Difference / Risk Increase |
|---|---|
| Complication rates | In the 12.3% PEM group vs non‑malnourished in THA patients, complication risk (within 6 months) was much higher at 44.4% vs 7.8%. |
| Wound complications |
Patients with hypoalbuminemia (low albumin) show significantly higher rates of wound healing issues after knee replacement. |
| Length of hospital stay (LOS) | Malnourished patients tend to stay in the hospital significantly longer as well, with lengths extending over 3 days in the hospital for some total hip replacement patients. |
| Infections / Surgical Site Infection (SSI) | Increased risk of post‐operative infections when malnutrition (specifically low serum albumin levels) is present. |
| Biomechanical & functional outcomes |
Another study even showed better outcomes with respect to post-operative pain, symptoms, and even knee biomechanics after TKA when patients had a better nutritional status. |
Why Malnutrition Causes Poorer Outcomes
Here are some of the biological reasons why this correlation is so strong:
-
Reduced Immune Function & Higher Infection Risk
Poor nutrition, especially low protein and key micronutrients (vitamin C, zinc, vitamin D), impairs immune system capacity. This increases susceptibility to surgical site infections and delayed wound healing during and after a major surgery. -
Poor Tissue Repair & Healing
Collagen formation, bone healing, and soft tissue repair require adequate proteins and nutrients. Just like when we exercise, we break and tear muscle fibers (where soreness comes from) so that they can rebuild and come back stronger. Your muscles and tissues experience a very similar situation to surgery. Malnutrition slows down and hampers these processes. -
More Muscle Loss (Sarcopenia)
Surgery + immobility lead to rapid muscle loss. Without good nutritional reserves, patients lose strength faster and regain it less efficiently. In turn impacting mobility, independence, and many other negative outcomes.
How Can Patients Prevent Malnutrition Before Surgery?
If you or a loved one is preparing for joint replacement, here are a few steps to reduce malnutrition risk and improve outcomes:
1. Get Screened Early
Ask your surgeon or primary care doctor to check markers like albumin, total lymphocyte count, body weight changes, and possibly GLIM criteria. Early detection is half the battle.
2. Improve Protein & Caloric Intake
- Aim for higher protein, lean meats, and protein supplements if needed
- Ensure you’re eating enough calories (don’t go into surgery in a calorie deficit unless specified by your surgeon)
- Consider preoperative oral nutritional supplements if you have a reduced appetite
3. Include Key Micronutrients
- Vitamin D, C, zinc, iron are among the most important
- Correct deficiencies ahead of surgery
- Consider taking a daily multivitamin to fill any vitamin or mineral gaps in your diet
4. Hydration
- Dehydration worsens metabolic stress and reduces perfusion
- Make sure water and electrolytes are well-maintained
5. Work with Nutrition Professionals
- Registered dietitians can give individualized plans
- Consider supplements specifically tailored for your preoperative needs as a patient
Conclusion: Nutrition Isn’t Optional—It’s Essential
Malnutrition isn’t something most patients think about before hip or knee replacement, but it should be.
The evidence is quite clear as we've shown: poor nutritional status is associated with higher complication rates, slower healing, longer hospital stays, and reduced long-term function. And yet, malnutrition is often never discussed in appropriate detail pre- or postoperatively.
The good news? Nutrition is one of the few things you have the power to improve upon before surgery.
By working with your care team, addressing any deficiencies, increasing protein intake, and preparing your body with the nutrients it needs, you can ensure a smoother, safer, and faster recovery.