Ageing may be conceptualized as a process of progressively increased entropy coupled with reduction and subsequently failure of the homeostatic mechanisms 1. Aging process may cause several modifications in muscle strength, postural control, balance, and gait, which are considered the main components of frailty 2. A decline in physical function and significant increases in the risk for disability and dependence are typical of elderly adults. Frailty is a geriatric syndrome associated with increased vulnerability of older adults to stressors and decreased ability to regain physiological functions after a destabilizing event 3,4. It is highly prevalent in people older than 65 years (7-16.3%) and can increase, up to 25% in people over 85 years 5,6 .There is general consensus that frailty results from underling physiologic and/or biologic alterations that Abstract Objectives: Frailty is a geriatric syndrome associated with increased vulnerability of older adults. Knee osteoarthritis (OA) is the most prevalent joint disease and one of the leading causes of disability and poor physical activity (PA) of elderly individuals worldwide. Total knee arthroplasty TKA has been recognized as an effective surgical treatment in end-stage of knee OA. There is a lack of consensus regarding the universally accepted rehabilitation protocol for frail elderly subjects after TKA. Aim: to evaluate the potential benefits in functional ambulation (FA) and PA among frail elderly Bulgarian subjects underwent TKA, a novel group-based rehabilitation protocol was performed from the subjects. Materials and methods: A total of 130 frail elderly Bulgarian TKA recipients (67 women and 63 men aged 72, 69 ± 0.44,) were included. FA was assessed by the six-minute walking distance (6MWD). PA was evaluated by the PASE questionnaire. Participants were evaluated one week before TKA, as well as 3 and 6 months after the group-based rehabilitation. Results: Significant increase in FA was observed at the third and sixth month after the group-based intervention (p< 0.001). PASE score, was increased at the third and sixth month after the group-based intervention (p<0.001, r 2 =0.74). Conclusions: Our results suggest that the applied group-based intervention led to a significant improvement in FA as well as in PA of frail elderly subjects over the first six months after the group-based intervention.