The Effects of PNF Stretching on Knee Motion Following TKA

Proprioceptive neuromuscular facilitation（PNF） is defined as a treatment method that promotes or hastens the response of the neuromuscular mechanism through stimulation of proprioceptors within the related muscles or joints. PNF stretching technique is a therapeutic technique using the PNF concept to the related muslces either to increase neuro-inhibition mechanism for releasing muscle spasm and elongating muscle length, or to increase neuro-excitation mechanism for enhancing muscle strength. Improvement in range of motion using PNF stretching technique has been reported superior to other techniques in previous literature, but those studies have only been done in healthy adults. Less is known in the effect of PNF stretching on improvement in joint restriction. Range of motion limitation usually disturbed the patients with total knee arthroplasty. PNF stretching techniques has been used frequently for patients with total knee arthroplasty in clinical practice to increase range of motion effectively and reduced knee pain during exercise. However there is no evidence-based research in such a technique for patients with total knee arthroplasty. This research project, therefore, will explore application of PNF stretch in changes of knee flexion, pain, muscle strength, and function of the lower extremity following total knee arthroplasty.

Purposes： To investigate immediate and short term effects on angle of knee flexion, intensity of pain, strength of the knee extensor, and function of the lower extremity by using PNF stretching technique in patients with total knee arthroplasty.

Method： Sixty patients who received total knee arthroplasty in National Taiwan University Hospital will be recruited in this study. They will be allocated randomly into either experimental or control groups. Conventional physical therapy will be given to all participants. Besides, the experimental group will assume PNF stretching technique from the third post-operative day to the day of discharge. This technique will be executed by the same physical therapist, including 5 trials of isometric knee extension for 6 s, followed by active knee flexion to the maximum range immediately, and holding for 10s. The rest interval will be 10 s. For the control group, passive stretch technique with the same treatment time will be given, instead. All participants will be asked to do home exercises after discharged from the hospital. The outcome measures will be given before and after the first session treatment on the same day, on the day of discharge, and one month after the operation. The variables measured will be (1) knee flexion angle measured with a universal goniometer, (2) maximum voluntary isometric strength of the knee extensor measured with a hand-held dynamometer, (3) pain score using pain visual analog scale, (4) function performance of the lower extremity measured with timed up and go test, (5) Knee Injury and Osteoarthritis Outcome Score (KOOS) to record 5 dimensions including the symptoms, stiffness, pain, difficulties in knee functions and/or daily activities, limitations in sports or recreational participation, and quality of life.