Effect of a Milk Protein Concentrate Supplement on Muscle Recovery and Oxidative Stress Following Knee and Hip Arthroplasty: A Randomized Control Trial

Background: Postoperative rehabilitation following Total Knee or Hip arthroplasty (TKA, THA respectively) for end-stage osteoarthritis is frequently characterized by oxidative stress and chronic-inflammation-induced muscle atrophy. This study investigated the efficacy of a milk protein concentrate supplement (MCPS) on oxidative stress, inflammation markers, and functional regains in patients undergoing TKA or THA. Methods: 88 participants (aged 55–80 years) were allocated to either an Intervention Group (IG, n = 44), receiving the MPCS, or a Control Group (CG, n = 44), following conventional nutrition for 15 weeks. Appendicular skeletal muscle mass (ASMM) was measured using bioelectrical impedance analysis and functionality through handgrip strength, gait speed, and static balance. 8-Isoprostane levels were quantified in plasma samples using the Enzyme-Linked Immunosorbent Assay(ELISA) method. C Reactive Protein (CRP) levels in serum specimens were measured. Data analysis was conducted, with adjustments made for age, gender, and comorbidities. Results: The IG demonstrated a significant increase in ASMM (Adj. mean change, Δ = +2.34 kg, 95% CI: 1.99 to 2.69, p < 0.001) and ASMM Index (Δ = +0.82 kg/m2, 95% CI: 0.64 to 1.00, p < 0.001) compared to the CG. Functional measurements also showed significant improvements in the IG, including Handgrip Strength (Δ = +4.40 kg, p < 0.001), Gait Speed (Δ = +0.23 m/s, p < 0.001), and the 2-Minute Walk Test (Δ = +12.02 m, p = 0.026). Regarding biochemical markers, the IG showed a significant reduction in plasma F2-isoprostane levels (Δ = −29.19, p < 0.001), CRP levels (Δ = −0.69 mg/L, p = 0.004), and PTH levels (Δ = −27.41 pg/mL, p < 0.001). A negative association between lipid peroxidation (8-isoprostanes) and ASMM was confirmed. Conclusions: Structural nutritional intervention can effectively mitigate catabolic stress triggered by surgical treatment. Implementing such strategies into orthopedic care offers a practical approach to treat challenges often associated with postoperative muscle loss.