by Sarah Voelkel Feierstein PT, DPT, OCS, CMPT


There is increasing evidence of the importance of adequate Vitamin D levels on muscle function and performance. Vitamin D is essential for calcium homeostasis and bone turnover which are essential following orthopedic surgeries. Total knee arthroplasties (TKAs) are a type of orthopedic surgery utilized for pain relief and improving quality of life in patients with end stage knee osteoarthritis (OA). The role of Vitamin D and its influence on functional recovery following TKA is not clearly established. The authors of the article, Vitamin D deficiency adversely affects early post‑operative functional outcomes after total knee arthroplasty, observed the effect of Vitamin D deficiency on post-operative functional outcomes following TKA.

Materials and Methods:

Ninety-two patients with a diagnosis of primary knee OA and scheduled for a unilateral TKA were included in the study. Patients were excluded if they had taken Vitamin D supplementation or had other comorbidities. Blood serum Vitamin D levels were obtained and the participants were divided into two categories: Vitamin D deficient (<12 ng/mL) and Vitamin D sufficient (>12ng/mL).

Following the surgeries, patients were scored on the American Knee Society Score (KSS) and four performance tests which included the alternative step test (AST), six-meter walk test (SMT), sit to stand test (STS) and timed up and go test (TUGT). Patients performed these tests one day before and three months after their TKA.

  • KSS: The KSS includes both a clinical and a functional portion. The clinical KSS includes pain, stability, and range of motion as the main parameters with deductions for flexion contractures, extension lag, and malalignment. The functional KSS includes walking distance and stair climbing with deductions for the use of a walking aid.
  • AST: This test is performed by alternatively placing the entire right and left foot as fast as possible on a step.
  • SMT: This test measures walking speed along a six-meter course.
  • STS: The number of times a participant can perform a sit to stand transfer with arms folded in thirty seconds is recorded.
  • TUGT: The participant is timed from rising from a chair wand walking around a cone 3 meters distance and returning to the chair.


There were no differences in the study population with respect to demographic data and clinical characteristics such as age, gender, BMI, and side of the surgery. There were no differences between groups in terms of post-operative clinical KSS. The man post-operative functional KSS was significantly lesser in the Vitamin D deficient group versus the non-deficient group. Additionally, the mean value times for the post-operative AST and SMT wee significantly longer in the Vitamin-D deficient group than in the non-deficient group. Both the STS and TUGT demonstrated high values for mean time taken in the Vitamin D deficient group but they were not statistically significant.


The most important finding of the present study was that early post-operative outcomes following TKA were affected by patients’ preoperative vitamin D status, and those in the vitamin D-deficient group had significantly poorer post-operative outcomes. Recent evidence suggests that Vitamin D deficiency associated with the development and progression of OA, though the underlying pathophysiology is unclear. There is also increasing evidence on the important role played by vitamin D in skeletal muscle pathology and supplementation of Vitamin D increase diameter of muscles. Because TKA results in substantial injury to the extensor mechanism of the knee, it is pertinent to evaluate the association between Vitamin D levels and functional recovery following TKA. Since vitamin D deficiency can usually be corrected by 6 weeks of oral supplementation, preoperative vitamin D supplementation may be considered for patients with deficiencies.

Conclusion and Clinical Implications:  

In the current study, early post-operative functional outcomes following TKA appear to be adversely affected by vitamin D deficiency. Surgeons should confirm vitamin D levels before performing a TKA and consider preoperative supplementation if necessary. As therapists, we many patients prior to their TKA surgeries and it is important to discuss this evidence with patients to determine whether supplementation is indicated due to the correlation between Vitamin D sufficiency and improved clinical outcomes post-operatively.


Shin, K-Y., Park, K., Moon, S-H., Yang, I., Choi, H., Lee, W (2017). Vitamin D deficiency adversely affects early post‑operative functional outcomes after total knee arthroplasty. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA), Vol 25:3424-3430.