Background
Degenerative knee disease (osteoarthritis in the knee which affects the joint lining and menisci) is the most common cause of knee pain, swelling and stiffness in the knee joint which leads to difficulty in walking. The cartilage in the knee joint is damaged, resulting in friction in the joint surfaces and formation of new bone in severe cases. Arthroscopic knee surgery removes damaged cartilage and loose tissue and smooths the knee joint surfaces.
Study characteristics
We included 16 randomised trials (2105 participants) published up to 16 April 2021. Trials were conducted in Canada, Denmark, Finland, Italy, Norway, Pakistan, South Korea, Spain, Sweden, Netherlands and USA.
Overall, 56% of participants were women. The average age of participants ranged from 46 to 65 years and the average duration of symptoms ranged from 1.6 months to 4.4 years. Of the nine trials reporting their funding source, none received funding from industry. The other seven trials did not report any funding source.
We limit reporting to the main comparison, arthroscopic surgery versus placebo (dummy or sham) surgery.
Key results
Compared with placebo surgery, arthroscopic surgery had little benefit:
Pain (lower scores mean less pain)
Improvement in pain was 4.6 points better (0.02 better to 9 better) on a 0 to 100 point scale with arthroscopic surgery than with placebo, 3 months after surgery.
• People who had arthroscopic surgery rated their post-operative pain as 35.5 points.
• People who had placebo surgery rated their post-operative pain as 40.1 points.
Knee function (higher scores mean better function)
Improvement in knee function was 0.1 points better (3.2 worse to 3.4 better) on a 0 to 100 point scale with arthroscopic surgery than with placebo, 3 months after surgery.
• People who had arthroscopic surgery rated their post-operative knee function as 76.0 points.
• People who had placebo surgery rated their post-operative knee function as 75.9 points.
Knee-specific quality of life (higher scores mean better quality of life)
Improvement in knee-specific quality of life was 5.6 points better (0.4 better to 10.7 better) on a 0 to 100 point scale with arthroscopic surgery than with placebo, 3 months after surgery.
• People who had arthroscopic surgery rated their post-operative quality of life as 75.3 points.
• People who had placebo surgery rated their post-operative quality of life as 69.7 points.
Treatment success (rated by participants)
8% more people rated their treatment a success (25% fewer to 63% more), or 8 more people out of 100, at up to 5 years after surgery.
• 82 out of 100 people reported treatment success with arthroscopic surgery.
• 74 out of 100 people reported treatment success with placebo surgery.
Serious adverse events
2% more people (2% fewer to 10% more) had serious adverse events, or 2 more people out of 100, at up to 5 years after surgery.
• 8 out of 100 people reported serious adverse events with arthroscopic surgery.
• 6 out of 100 people reported serious adverse events with placebo surgery.
Total adverse events
2% more people (3% fewer to 11% more), had adverse events, or 2 more people out of 100, at up to 5 years after surgery.
• 17 out of 100 people reported adverse events with arthroscopic surgery.
• 15 out of 100 people reported adverse events with placebo surgery.
Subsequent knee surgery
2% more people (0.1% fewer to 9% more), had subsequent knee surgery, or 2 more people out of 100, at up to 5 years.
• 4 out of 100 people had knee replacement or osteotomy (knee surgery that reshapes bone) with arthroscopic surgery.
• 2 out of 100 people had knee replacement or osteotomy with placebo surgery.
Certainty of the evidence
We are confident that knee arthroscopy does not provide any clinically important benefits in terms of pain and function. We are moderately confident that knee arthroscopy probably does not provide any clinically important benefits in knee-specific quality of life over a placebo procedure. Knee arthroscopy may not increase participant-reported success compared with placebo. We have little confidence in the evidence because of differences across trials in reporting success and the small number of events. We are less certain of the risk of serious and total adverse events in arthroscopy versus placebo surgery: the evidence was uncertain because of the small number of events and incomplete reporting of study information.
Adverse events associated with surgery include total knee replacement, osteotomy, repeat arthroscopy, arthroscopy in opposite knee, cutaneous nerve lesion (damage to nerves in the skin), deep or superficial infection, general knee pain, swelling, instability, stiffness or decreased range of motion in the affected or opposite knee, haemarthrosis (bleeding into the knee joint), death, acute myocardial infarction (heart attack), hypoxaemia (decreased oxygen in the blood), deep vein thrombosis (blood clot in the deep veins), tendonitis (inflammation of tendons), pain from fall or other trauma, rupture of a Baker's cyst (a fluid-filled sac behind the knee), and back or hip or foot pain.
Arthroscopic surgery may or may not lead to slightly more subsequent knee surgery (replacement or osteotomy) than the placebo procedure.
Arthroscopic surgery provides little or no clinically important benefit in pain or function, probably does not provide clinically important benefits in knee-specific quality of life, and may not improve treatment success compared with a placebo procedure. It may lead to little or no difference, or a slight increase, in serious and total adverse events compared to control, but the evidence is of low certainty. Whether or not arthroscopic surgery results in slightly more subsequent knee surgery (replacement or osteotomy) compared to control remains unresolved.
Arthroscopic knee surgery remains a common treatment for symptomatic knee osteoarthritis, including for degenerative meniscal tears, despite guidelines strongly recommending against its use. This Cochrane Review is an update of a non-Cochrane systematic review published in 2017.
To assess the benefits and harms of arthroscopic surgery, including debridement, partial menisectomy or both, compared with placebo surgery or non-surgical treatment in people with degenerative knee disease (osteoarthritis, degenerative meniscal tears, or both).
We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and two trials registers up to 16 April 2021, unrestricted by language.
We included randomised controlled trials (RCTs), or trials using quasi-randomised methods of participant allocation, comparing arthroscopic surgery with placebo surgery or non-surgical interventions (e.g. exercise, injections, non-arthroscopic lavage/irrigation, drug therapy, and supplements and complementary therapies) in people with symptomatic degenerative knee disease (osteoarthritis or degenerative meniscal tears or both). Major outcomes were pain, function, participant-reported treatment success, knee-specific quality of life, serious adverse events, total adverse events and knee surgery (replacement or osteotomy).
Two review authors independently selected studies for inclusion, extracted data, and assessed risk of bias and the certainty of evidence using GRADE. The primary comparison was arthroscopic surgery compared to placebo surgery for outcomes that measured benefits of surgery, but we combined data from all control groups to assess harms and knee surgery (replacement or osteotomy).
Sixteen trials (2105 participants) met our inclusion criteria. The average age of participants ranged from 46 to 65 years, and 56% of participants were women. Four trials (380 participants) compared arthroscopic surgery to placebo surgery. For the remaining trials, arthroscopic surgery was compared to exercise (eight trials, 1371 participants), a single intra-articular glucocorticoid injection (one trial, 120 participants), non-arthroscopic lavage (one trial, 34 participants), non-steroidal anti-inflammatory drugs (one trial, 80 participants) and weekly hyaluronic acid injections for five weeks (one trial, 120 participants). The majority of trials without a placebo control were susceptible to bias: in particular, selection (56%), performance (75%), detection (75%), attrition (44%) and selective reporting (75%) biases. The placebo-controlled trials were less susceptible to bias and none were at risk of performance or detection bias. Here we limit reporting to the main comparison, arthroscopic surgery versus placebo surgery.
High-certainty evidence indicates arthroscopic surgery leads to little or no difference in pain or function at three months after surgery, moderate-certainty evidence indicates there is probably little or no improvement in knee-specific quality of life three months after surgery, and low-certainty evidence indicates arthroscopic surgery may lead to little or no difference in participant-reported success at up to five years, compared with placebo surgery.
Mean post-operative pain in the placebo group was 40.1 points on a 0 to 100 scale (where lower score indicates less pain) compared to 35.5 points in the arthroscopic surgery group, a difference of 4.6 points better (95% confidence interval (CI) 0.02 better to 9 better; I2 = 0%; 4 trials, 309 participants). Mean post-operative function in the placebo group was 75.9 points on a 0 to 100 rating scale (where higher score indicates better function) compared to 76 points in the arthroscopic surgery group, a difference of 0.1 points better (95% CI 3.2 worse to 3.4 better; I2 = 0%; 3 trials, 302 participants).
Mean post-operative knee-specific health-related quality of life in the placebo group was 69.7 points on a 0 to 100 rating scale (where higher score indicates better quality of life) compared with 75.3 points in the arthroscopic surgery group, a difference of 5.6 points better (95% CI 0.36 better to 10.68 better; I2 = 0%; 2 trials, 188 participants). We downgraded this evidence to moderate certainty as the 95% confidence interval does not rule in or rule out a clinically important change.
After surgery, 74 out of 100 people reported treatment success with placebo and 82 out of 100 people reported treatment success with arthroscopic surgery at up to five years (risk ratio (RR) 1.11, 95% CI 0.66 to 1.86; I2 = 53%; 3 trials, 189 participants). We downgraded this evidence to low certainty due to serious indirectness (diversity in definition and timing of outcome measurement) and serious imprecision (small number of events).
We are less certain if the risk of serious or total adverse events increased with arthroscopic surgery compared to placebo or non-surgical interventions. Serious adverse events were reported in 6 out of 100 people in the control groups and 8 out of 100 people in the arthroscopy groups from eight trials (RR 1.35, 95% CI 0.64 to 2.83; I2 = 47%; 8 trials, 1206 participants). Fifteen out of 100 people reported adverse events with control interventions, and 17 out of 100 people with surgery at up to five years (RR 1.15, 95% CI 0.78 to 1.70; I2 = 48%; 9 trials, 1326 participants). The certainty of the evidence was low, downgraded twice due to serious imprecision (small number of events) and possible reporting bias (incomplete reporting of outcome across studies). Serious adverse events included death, pulmonary embolism, acute myocardial infarction, deep vein thrombosis and deep infection.
Subsequent knee surgery (replacement or high tibial osteotomy) was reported in 2 out of 100 people in the control groups and 4 out of 100 people in the arthroscopy surgery groups at up to five years in four trials (RR 2.63, 95% CI 0.94 to 7.34; I2 = 11%; 4 trials, 864 participants). The certainty of the evidence was low, downgraded twice due to the small number of events.