1. Introduction
ackground: The focus of the conventional treatment program after knee replacement surgery is on strengthening the quadriceps muscle and the Range of Motion (RoM) of the knee; however, the weakness of other thigh muscles is observed in patients with knee osteoarthritis. The present study aimed to evaluate the effects of strengthening the muscles around the hip joint on pain, RoM, Quality of Life (QoL), and performance in patients undergoing complete unilateral knee replacement surgery (Table 1). 


 2. Materials and Methods
This study was performed from the second-day post-surgery for 10 sessions daily among 24 subjects divided into the control [routine exercises + Transcutaneous Electrical Neural Stimulation (TENS) & Infra-Red (IR)] and treatment (control group + thigh muscle strengthening exercises) groups. The measurement criteria included pain, the amplitude of knee flexion and extension, QoL (the 36-Item Short Form Survey; SF-36)), Timed Up and Go (TUG) test, Step Test, Six-Minute Walk Test (6MWT), and Hip and Knee Muscle Strength test.
3. Results
All evaluation criteria were improved in both research groups, indicating the effectiveness of both presented approaches. Pain (P=0.03), extension range (P=0.007), TUG test and Step Test (P=0.033), and the strength of knee flexor muscles (P=0.023), thigh flexor (P=0.040), thigh extensor (P=0.028), thigh adjustor (P=0.040), and external hip rotator (P=0.047) provided a significant improvement in the experimental group, compared to the control group.
4. Discussion and Conclusion
According to the present study findings, both conventional physiotherapy and conventional physiotherapy combined with strengthening the thigh muscles can be effective in improving the results obtained after complete unilateral knee replacement surgery. The outcome of routine physiotherapy treatment with thigh muscle strengthening was more effective in some variables. Some studies revealed that thigh muscle strengthening in addition to routine treatment can be effective in improving functional outcomes months after surgery. Thus, physiotherapists are recommended to implement the tested method in this research to treat patients with complete one-sided replacement of the knee joint. Accordingly, they are suggested to use early strengthening of the thigh muscles in addition to the conventional treatment for this population.According to the present research results, both treatment approaches were effective on patients with unilateral total knee arthroplasty. Considering the better result of some of the outcome measures in the intervention group, the addition of hip strengthening exercises to knee exercises can be useful (Table 2 and 3).




Ethical Considerations
Compliance with ethical guidelines
This research was approved by the Research Ethics Committee of Iran University of Medical Sciences (IR.IUMS.REC.1396.9511340012) and it was registered in the Clinical Trial Registration Center (Code: IRCT 20150314021459N6).

Funding
The paper was extracted from the MA. thesis of the first author, Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran.

Authors' contributions
All authors met the standard criteria for writing based on the recommendations of the International Committee of Publishers of Medical Journals (ICMJE).

Conflicts of interest
The authors declared no conflicts of interest.

Acknowledgements
We want to thank the Vice-Chancellor for Research and Technology of Iran University of Medical Sciences for their help.

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