Rapid loss of muscle mass & strength is seen following injury.

This is further compounded by the stress of surgery.

Injury + Surgery = Compounded Stress

Healthy young men have a decrease of muscle size with immobilization, showing the greatest amount of atrophy in the quadriceps:

*-1.7% at 2 days

*-5.5% at 7 days

Associated Strength Loss:

*Leg extensor -19%

*Leg press -21%

*Calf strength -8%


Older patients experience a higher rate of post-surgical atrophy.

Muscle Loss Post TKA:

*1% per day 

*14.3% at 2 wks post op 

* 80% of this atrophy occurs during the first 2 wks post-op

*18% at 6 wks post-op


  • Post ACL Injury & Surgery

    *20% Loss of quad mass and strength post-injury

    *40% Loss of strength post-surgery


    Seto AJSM 1988

  • Post Total Knee Replacement

    *50-60% Loss of quad muscle strength post TKR


    Minzer JBJS 2005

  • Post Total Hip Replacement

    Despite high levels of pain relief post THR, patients continue to struggle with recovering normal strength and function years after surgery.

    *35% of participants reported moderate to severe activity limitations at 5 years.

    Singh J. Am. Geriatr. Soc. 2010

  • Muscle loss begins in as little as 48-hours of inactivity/injury, with the most significant loss within five days.

    50% drop in muscle protein synthesis by 2 wks.


    Biol Sci Med Sci. 2008

  • Effect of 10 days of bed rest on skeletal muscle in healthy older adults.

    After 3 days of hospitalization, elderly inpatients lost approx the amount of lean leg muscle as healthy older subjects experienced in 10 days of inactivity– approx 3-fold> greater loss of lean leg muscle mass than a younger cohort confined to bed for 28 days. (2,4)

    Kortebein JAMA 2007

  • NASA studies aimed to preserve muscle mass have demonstrated Targeted Nutritional Supplementation to preserve muscle loss even in extreme conditions such as 28 of days of bed rest.

    J Clin Endocrinol Metab 2004(4)

  • Targeted nutritional supplementation can improve muscle gain in the most challenging patients.

    HIV patients who were supplemented with ARG/GLUT/HMB for 8wks had a significant increase in LBM in comparison to placebo.

    Clark JPEN May-Jun 2000 (5)

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Muscle Loss References

(ref #1) Kortebein P, Symons TB, Ferrando A, et al., J Gerontol A Biol Sci Med Sci. 2008;63(10):1076‐1081.

(ref #2) Kortebein P, Ferrando A, Lombeida J, et al: Effect of 10 days of bed rest on skeletal muscle in healthy older adults. JAMA 2007;297:1772-1774.

(ref #3) Paddon-Jones D, Sheffield-Moore M, Cree MG, et al: Atrophy and impaired muscle protein synthesis during prolonged inactivity and stress. J Clin Endocrinol Metab 2006;91:4836-4841

(ref #4) Paddon-Jones D, Sheffield-Moore M, Urban RJ, et al: Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in humans during 28 days bedrest. J Clin Endocrinol Metab 2004;89:4351-4358

(ref #5) Robert. H. Clark MD, J Parenter Enteral Nutr May-Jun 2000;24(3):133-9.Nutritional Treatment for Acquired Immunodeficiency Virus-Associated Wasting Using β-Hydroxy β-Methylbutyrate, Glutamine, and Arginine: A Randomized, Double-Blind, Placebo-Controlled Study

(ref #6) Willey MC, Owen EC, Miller A, Glass N, Kirkpatrick T, Fitzpatrick D, Wilken J, Marsh JL, Reider L. Substantial Loss of Skeletal Muscle Mass Occurs After Femoral Fragility Fracture. J Bone Joint Surg Am. 2023 Sep 22. doi: 10.2106/JBJS.23.00353. Epub ahead of print. PMID: 37738373.