Background Knee arthroscopy (KA) is a routine orthopedic procedure recommended to repair cruciate ligaments and meniscus injuries and, in suitable cases, to assist the diagnosis of persistent knee pain. There is a small risk of thromboembolic events associated with KA. This systematic review aims to assess if pharmacological or non-pharmacological interventions may reduce this risk. This is an update of an earlier Cochrane Review. Objectives To evaluate the efficacy and safety of interventions - whether mechanical, pharmacological, or a combination of both - for thromboprophylaxis in adults undergoing KA. Search methods We used standard, extensive Cochrane search methods. The latest search date was 1 June 2021. Selection criteria We included randomized controlled trials (RCTs) and controlled clinical trials (CCTs), blinded or unblinded, of all types of interventions used to prevent deep vein thrombosis (DVT) in men and women aged 18 years and older undergoing KA. Data collection and analysis We used standard Cochrane methods. Our primary outcomes were pulmonary embolism (PE), symptomatic DVT, asymptomatic DVT, and all-cause mortality. Our secondary outcomes were adverse effects, major bleeding, and minor bleeding. We used GRADE criteria to assess the certainty of the evidence. Main results We did not identify any new studies for this update. This review includes eight studies involving 3818 adults with no history of thromboembolic disease. Five studies compared daily subcutaneous low-molecular-weight heparin (LMWH) versus no prophylaxis; one study compared oral rivaroxaban 10 mg versus placebo; one study compared daily subcutaneous LMWH versus graduated compression stockings; and one study compared aspirin versus no prophylaxis. The incidence of PE in all studies combined was low, with seven cases in 3818 participants. There were no deaths in any of the intervention or control groups. Low-molecular-weight heparin versus no prophylaxis When compared with no prophylaxis, LMWH probably results in little to no difference in the incidence of PE in people undergoing KA (risk ratio [RR] 1.81, 95% confidence interval [CI] 0.49 to 6.65; 3 studies, 1820 participants; moderate-certainty evidence). LMWH may make little or no difference to the incidence of symptomatic DVT (RR 0.61, 95% CI 0.18 to 2.03; 4 studies, 1848 participants; low-certainty evidence). It is uncertain whether LMWH reduces the risk of asymptomatic DVT (RR 0.14, 95% CI 0.03 to 0.61; 2 studies, 369 participants; very low-certainty evidence). LMWH probably makes little or no difference to the risk of all adverse effects combined (RR 1.85, 95% CI 0.95 to 3.59; 5 studies, 1978 participants; moderate-certainty evidence), major bleeding (RR 0.98, 95% CI 0.06 to 15.72; 1451 participants; moderate-certainty evidence), or minor bleeding (RR 1.79, 95% CI 0.84 to 3.84; 5 studies, 1978 participants; moderate-certainty evidence). Rivaroxaban versus placebo One study with 234 participants compared oral rivaroxaban 10 mg versus placebo. There were no cases of PE reported. Rivaroxaban probably led to little or no difference in symptomatic DVT (RR 0.16, 95% CI 0.02 to 1.29; moderate-certainty evidence). It is uncertain whether rivaroxaban reduces the risk of asymptomatic DVT because the certainty of the evidence is very low (RR 0.95, 95% CI 0.06 to 15.01). The study only reported bleeding adverse effects. No major bleeds occurred in either group, and rivaroxaban probably made little or no difference to minor bleeding (RR 0.63, 95% CI 0.18 to 2.19; moderate-certainty evidence). Aspirin versus no prophylaxis One study compared aspirin with no prophylaxis. There were no PE, DVT or asymptomatic events detected in either group. The study authors reported adverse effects including pain and swelling, but without clarifying which groups these occurred in. There were no bleeds reported. Low-molecular-weight heparin versus compression stockings One study with 1317 participants compared LMWH versus compression stockings. LMWH may lead to little or no difference in the risk of PE compared to compression stockings (RR 1.00, 95% CI 0.14 to 7.05; low-certainty evidence), but it may reduce the risk of symptomatic DVT (RR 0.17, 95% CI 0.04 to 0.75; low-certainty evidence). It is uncertain whether LMWH has any effect on asymptomatic DVT (RR 0.47, 95% CI 0.21 to 1.09; very low-certainty evidence). The results suggest LMWH probably leads to little or no difference in major bleeding (RR 3.01, 95% CI 0.61 to 14.88; moderate-certainty evidence), or minor bleeding (RR 1.16, 95% CI 0.64 to 2.08; moderate-certainty evidence). We downgraded the certainty of the evidence for imprecision due to overall small event numbers, for risk of bias due to concerns about lack of blinding, and for indirectness due to uncertainty about the direct clinical relevance of asymptomatic DVT detection. Authors' conclusions There is a small risk that healthy adults undergoing KA will develop venous thromboembolism (PE or DVT). We found moderate- to low-certainty evidence of little or no benefit from LMWH, or rivaroxaban in reducing this small risk of PE or symptomatic DVT. The studies provided very low-certainty evidence that LMWH may reduce the risk of asymptomatic DVT compared to no prophylaxis, but it is uncertain how this directly relates to incidence of DVT or PE in healthy people undergoing KA. There is probably little or no difference in adverse effects (including major and minor bleeding), but data relating to these outcomes were limited by low numbers of events in the studies reporting these outcomes.
