***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Therapeutic trials often attempt to “ blind ” patient and investigator to the true nature of treatments received , reducing the influences of conscious or subconscious prejudices . In drug trials , this is accomplished with placebo tablets , but blinding in trials of physical treatments is more problematic . This issue arose in a clinical trial of transcutaneous electrical nerve stimulation ( TENS ) for patients with chronic low back pain . Several study design features were incorporated to promote blinding : use of sham TENS units visually identical with real units , exclusion of potential subjects with previous TENS experience , avoidance of a crossover design and use of identical visit frequency , instructions and modifications in electrode placement . Subjects were asked not to discuss treatments with the clinicians who performed outcome assessment s. Both patients and clinicians were asked to guess actual treatment assignments at the trial 's end . Every patient in the true TENS group believed the unit was functioning properly , but the degree of certainty varied . In the sham TENS group , 84 % also believed they had functioning units , but their certainty was significantly less than in the active treatment group . Differences in patient perceptions did not affect compliance , as the two groups had similar dropout rates , appointment compliance , days of TENS use and daily duration of TENS use . Clinicians guessed treatments correctly 61 % of the time ( as opposed to 50 % expected by chance ) , again suggesting partial success in blinding . These efforts at blinding may partly explain the negative trial results for TENS efficacy . We conclude that complete blinding is difficult to achieve because of sensory difference in treatment and unintended communication between patient and examiner . Nonetheless , trials of physical treatments can achieve partial blinding with the techniques described here , and the success of blinding can be assessed with simple questions at study completion Thirty patients with chronic pain due to osteoarthrosis ( OA ) of the knee were enrolled in a r and omised double-blind cross-over trial of self-administered transcutaneous electrical nerve stimulation ( TENS ) and placebo TENS . Medication was st and ardised to paracetamol tablets only . As measured on visual analogue scales for pain relief 46 % of patients responded to active therapy and 43 % to placebo . The length of pain relief during active therapy was significantly longer than that during placebo . At the end of the trial more patients wanted to continue using active TENS in preference to placebo or their original medication . Although most of the parameters observed favoured active TENS , it was not possible to establish its clear superiority over placebo , because the response rate to placebo TENS was high and sustained for at least 3 weeks . This trial suggests that a longer study is required to establish the role of TENS as a therapeutic agent in the treatment of the pain of chronic arthritis A prospect i ve study of the use of transcutaneous neural stimulation ( TNS ) in 90 arthroscopic knee surgery pa tients was performed to determine : ( 1 ) if TNS is as effective as traditional pain medication in treating post operative knee pain ; and ( 2 ) if patients that had received TNS regain preoperative motion and strength quicker than the control population . The patients were divided into three equal groups . Group I consisted of patients with no TNS unit  , Group II had a " placebo " unit  , and Group III had a " live " unit . Preoperatively , each patient received an isokinetic muscle examination , orientation to the TNS unit , leg circumference measurements , and exercise instruction . An isokinetic muscle examination and leg circumference measurements were repeated at 1 , 3 , and 7 weeks postoperatively . Additionally , the amount of pain and medication required was analyzed . The results of the study indicated that the use of a TNS unit is an effective adjunct in decreasing postoperative pain in 93 % of patients . The amount of pain and total pain medication required was greatest in the control group , less in the placebo , and markedly reduced in the TNS group . A comparison among the three groups revealed that the TNS group regained the following preoperative values 1 month sooner than the other two groups ( 3 as opposed to seven weeks postoperatively ) : isokinetic power in flexion and extension ( P < 0.05 ) , range of motion ( P < 0.02 ) , and leg volume ( P < 0.05 ) . There was no correlation between the pain and irregular wave forms on the isokinetic graph . The only compli cation noted was skin irritation at the electrode sites . TNS has been shown to be a significant benefit in the treatment of postoperative knee pain and in hastening recovery of muscular function through a full range of motion Thirty-six non-hospitalized subjects with chronic pain from OA of the knee participated in an evaluation of transcutaneous electrical nerve stimulation ( TENS ) and naproxen , an NSAID . All pre-experiment treatment was withdrawn . Each subject experienced in some order three 3-week treatment phases : NSAID plus placebo TENS ; TENS plus placebo drug ; and double placebo . A broad range of pain measures was used , including daily diary ratings , and four-times-per-day ratings entered into a small electronic data logger ( the PIPER ) worn by the subject . A substantial placebo response occurred across all conditions , which may have masked treatment differences . Broad comparisons across subjects , combining the four main measures of pain , found no significant differences among the three experimental treatments . Analysis of diary and PIPER data for individuals suggested that , in a small minority of subjects , the NSAID plus placebo TENS combination may be more effective than double placebo . The PIPER ratings seemed to tap aspects of the pain experience different from those captured by conventional measures , suggesting the value of very frequent pain assessment s , such as those entered by a subject into the PIPER , in the study of chronic pain Patients suffering from pain due to osteoarthritis of the hip and knee participated in a double-blind placebo controlled trial using daily Codetron home care units for 6 weeks over the tibial , saphenous , popliteal and sciatic nerves , and tender points . Seventy-four percent of patients in the real Codetron ( Group A ) and 28 % of the patients in sham Codetron ( Group B ) improved their pain level more than 25 % as measured by visual analogue scale . The difference in pain improvement in the two groups was statistically significant ( p < 0.02 using Fisher 's exact probability ratio ) Other functional parameters proved to be insensitive to change in this study . This is highly suggestive of beneficial effect of chronic pain conditions such as osteoarthritis Abstract Ten patients with pain due to osteoarthritis of the knee were treated in a double‐blind cross‐over study with two weeks of transcutaneous electrical nerve stimulation ( TENS ) and placebo . There was statistically significant pain relief by TENS and half of the patients chose to continue using TENS for pain control after the test month . However , at one year 's follow‐up , only two patients had sufficient benefit to continue using the device 
    Output:
    
Pain relief from active TENS and AL-TENS treatment was significantly better than placebo treatment .
Knee stiffness also improved significantly in active treatment group compared to placebo .
Different modes of TENS setting ( High Rate and Strong Burst Mode TENS ) demonstrated a significant benefit in pain relief of the knee OA over placebo .
REVIEW ER 'S CONCLUSIONS TENS and AL-TENS are shown to be effective in pain control over placebo in this review .
More well design ed studies with a st and ardized protocol and adequate number of participants are needed to conclude the effectiveness of TENS in the treatment of OA of the knee