Study characteristics and main results of included studies
| Author, year of publication | Study design | Location: medial/lateral, type of tear | Sample size: N | Age: year mean±SD (range) | Follow-up: year mean±SD (range) | Female: N (%) | Risk of bias (type of bias) | Independent variables | Outcome measure | Main conclusions (P value) |
| Aune et al, 199518 | Prospective cohort | Medial, all tear types | 93 | Median 45 (12–75) | 3.5, SD: NM (2.1–4.2) | 28 (30) | High (Sel., Conf.) | Chondral damage | Lysholm | Chondral damage: worse outcome (P<0.04) |
| Bin et al, 200428 | Retrospective cohort | Medial posterior horn, radial tears | 85 (96 knees) | 56, SD: NM (31–77) | 2.3, SD: NM (1–4.3) | 70 (73) | High (Sel., Conf.) | Tear depth | Lysholm | NS (P>0.05) |
| Bin et al, 200849 | Retrospective cohort | Medial, all tears | 68 | 63, SD: NM (51–77) | 4.3, SD: NM (3.1–6.9) | 63 (93) | High (Sel., Conf.) | Location of chondral damage | Lysholm, VAS | NS (P=0.16) |
| Bolano et al, 199336 | Retrospective cohort | Medial and lateral, all tears | 50 | 30, SD and range: NM | 5.6, SD and range: NM | 5 (10) | Moderate (Conf.) | Age, sex, duration of symptoms (</>12 months), tear location/type, chondral damage | Lysholm, Tegner | Higher age, long duration of symptoms, horizontal/complex tear and chondral damage: worse outcome (P<0.05) Sex, tear location: NS (P value NM) |
| Bonneux et al, 200242 | Retrospective cohort | Lateral, all tears | 29 (31 knees) | 25, SD and range: NM | 8±1.5 (range NM) | 9 (36) | High (Sel., Conf.) | Sex, BMI, traumatic/non-traumatic, sport level, amount of resected tissue (subtotal/limited) | IKDC, Lysholm | Larger amount of resected tissue (subtotal, >50%): worse outcome (P=0.02) Sex, BMI, traumatic/non-traumatic, sport level: NS (P=0.3, 0.4, 0.2, 0.4 resp.) |
| Chatain et al, 200343 | Retrospective cohort | Medial and lateral, all tears | 471 | 37±12 (13-70) | 11±1.3 (10–15) | 99 (21) | High (Sel., Conf.) | Age, sex, BMI, sport level, leg alignment, tear location (medial/lateral), tear type, chondral damage, amount of resected tissue (rim involved yes or no) | IKDC | Larger amount of resected tissue (rim involved): worse outcome (P=0.004) Age, sex, BMI, sport level, leg alignment, tear location, type, chondral damage: NS (P≥0.05) |
| Covall et al, 199238 | Retrospective cohort | Medial and lateral, all tears | 46 (56 knees) | 57, SD: NM (45–72) | 5.4±1.3 (3–8) | 6 (11) | High (Sel., Conf.) | Leg alignment, radiological knee OA | Modified Lysholm, Tegner | Radiological knee OA: worse outcome (P<0.05) Valgus leg alignment: better outcome (P<0.001) |
| Erdil et al, 201323 | Retrospective cohort | Medial and lateral, all tears | 1090 | 43, SD: NM (18–50) | 1, SD and range: NM | 423 (35) | Moderate (Conf.) | Sex, BMI, side of knee (left/right), tear type | IKDC, Lysholm, Oxford | Higher BMI: worse outcome (P<0.001) Sex, side of knee, tear type: NS (P=0.88 for sex, P value for the others NM |
| Fauno et al, 199348 | Retrospective cohort | Medial and lateral, all tears | 88 | 30, SD: NM (13–62) | 8.6 SD: NM (8–11.6) | 24 (27) | Moderate (Conf.) | Age, sex, sport level, sport type, tear type, chondral damage | Lysholm | Higher age, ball sports, flap-tears: worse outcome (P=0.002, 0.0001, 0.004 resp.) Sex, sport level, chondral damage: NS (P value NM) |
| Ghislain et al, 201647 | Retrospective cohort | Medial and lateral, all tears | 117 | 47±9 (18–72) | 4±0.3 (range NM) | 69 (59) | High, (Sel., Conf.) | Traumatic/non-traumatic | Lysholm, SF-36 | Non-traumatic: worse outcome (P<0.0001) |
| Han et al, 201039 | Retrospective cohort | Medial posterior horn, root tears | 46 | 59, SD: NM (48–85) | 6.5, SD: NM (5–8.6) | 36 (78) | High, (Sel., Conf.) | Radiological knee OA, chondral damage | Lysholm | Radiological knee OA, chondral damage: worse outcome (P=0.004, 0.002 resp.) |
| Haviv et al, 201533 | Retrospective cohort | Medial, complex tears | 135 | 51, SD: NM (20–80) | 2, SD and range: NM | 49 (36) | High, (Sel., Conf.) | BMI, chondral damage | Lysholm, VAS | Chondral damage: worse outcome in women (P=0.05) Higher BMI: worse outcome in men (P=0.02) |
| Haviv et al, 201619 | Prospective cohort | Medial and lateral, all tears | 201 | 44±15 (range NM) | 1±0.3 (range NM) | 68 (34) | High, (Sel., Conf.) | Age, sex, chondral damage | Lysholm, Tegner | Older age, female, chondral damage: worse outcome (P<0.0001) |
| Haviv et al, 201674 | Retrospective cohort | Medial and lateral, all tears | 86 | 48±13 (range NM) | 1±0.3 (range NM) | 24 (28) | High, (Sel., Conf.) | Traumatic/non-traumatic | Lysholm, Tegner | Traumatic/non-traumatic: NS (P=0.24) |
| Haviv et al, 201637 | Retrospective cohort | Medial and lateral, all tears | 187 | 46±15 (range NM) | 1±0.3 (range NM) | 51 (27) | High, (Sel., Conf.) | Duration of symptoms | Lysholm | Longer duration of symptoms: worse outcome (P=0.01) |
| Hoser et al, 200146 | Retrospective cohort | Lateral, all tears | 29 (31 knees) | 44±13 (range NM) | 10.3±0.6 (9.2–12.1) | 5 (17) | High, (Sel., Conf.) | Amount of resected tissue | Lysholm | Amount of resected tissue: NS (P value NM) |
| Hulet et al, 200173 | Retrospective cohort | Medial, all tears | 57 (74 knees) | 36±11 (range NM) | 12±1 (range NM) | 11 (19) | High, (Sel., Conf.) | Age, sex, traumatic/non-traumatic, activity, tear type, chondral damage | IKDC | Age, sex, traumatic/non-traumatic, activity, tear type, chondral damage: NS (P value NM) |
| Hulet et al, 201545 | Retrospective cohort | Lateral, all tears | 89 | 35±13 (range NM) | 22±3 (range NM) | 33 (37) | High, (Sel., Conf.) | Sex, tear type, amount of resected tissue | IKDC, KOOS | Larger amount of resected tissue: worse outcome (P value NM) Sex, tear type: NS (P value NM) |
| Jaureguito et al, 199522 | Retrospective cohort | Lateral, all tears | 26 (27 knees) | 30, SD: NM (14–57) | 8, SD: NM (5.5–11.3) | NM | High, (Sel., Conf.) | Age, leg alignment, tear type | Lysholm | Leg alignment, tear type, age: NS (P=0.83, 0.45, NM resp.) |
| Kim et al, 201330 | Retrospective cohort | Medial and lateral, horizontal tears | 40 | 34, SD: NM (16–40) | 2, SD and range: NM | 24 (60) | Moderate (Conf.) | Traumatic/non-traumatic | IKDC, Lysholm | Traumatic/non-traumatic: NS (P=0.41) |
| Kim et al, 201444 | Retrospective cohort | Medial and lateral, all tears | 312 | 41, SD: NM (13–62) | 5, SD and range: NM | 120 (38) | High (Sel., Conf.) | Amount of resected tissue (vertical resection/horizontal resection/subtotal | IKDC | Larger amount of resected tissue (subtotal): worse outcome (P<0.001) |
| Kim et al, 201631 | Retrospective cohort | Medial, horizontal tears | 98 (100 knees) | 40±8 (range NM) | 1.5±1.5 range NM) | 21 (21) | High (Sel., Conf.) | Tear type (direction) | IKDC, Tegner | Tear type: NS (P value NM) |
| Maletius et al, 199635 | Retrospective cohort | Medial and lateral, all tears | 40 | 29, SD: NM (18–40) | 13, SD: NM (12–15) | 8 (20) | Low | Age, chondral damage | Lysholm, Tegner | Higher age: worse outcome (P=0.03) Chondral damage: NS (P value NM) |
| Menetrey et al, 200227 | Retrospective cohort | Medial, all tears | 32 | 60, SD: NM (51–74) | 6, SD: NM (3–7) | 11 (34) | High (Sel., Conf.) | Traumatic/non-traumatic | HSS Knee Score | Non-traumatic: worse outcome (P=0.009) |
| Ozkoc et al, 200829 | Retrospective cohort | Medial, radial root tears | 67 | 56, SD: NM (38–70) | 4.8, SD and range: NM | 47 (70) | High (Sel., Conf.) | BMI | Lysholm | BMI: NS (P>0.01) |
| Rockborn et al, 199525 | Retrospective cohort | Medial and lateral, all tears | 43 | 19, SD: NM (15–22) | 13, SD: NM (11–15) | 6 (14) | Moderate (Conf.) | Amount of resected tissue (partial/subtotal) | Lysholm, Tegner | Larger amount of resected tissue (subtotal): worse outcome (P=0.02) |
| Rosenberger et al, 201020 | Prospective cohort | Medial and lateral, all tears | 180 | 48, SD: NM (17–78) | 1, SD and range: NM | 79 (44) | High (Sel., Conf.) | Age, sex, BMI, activity, fitness, prior injury, chondral damage | Lysholm, Tegner | Female, lower fitness, prior injury, chondral damage: worse outcome (P=0.0001, 0.033, 0.002, 0.028 resp.) Age, BMI, activity: NS (P=0.32, 0.20, 0.42 resp.) |
| Scanzello et al, 201321 | Prospective cohort | Medial and lateral, all tears | 33 | Median 45 (IQR 40–53) | 2, SD and range: NM | 12 (36) | High (Sel., Conf.) | Synovial inflammation | Lysholm | Synovial inflammation: NS (P=0.14) |
| Scheller et al, 200172 | Retrospective cohort | Lateral, all tears | 75 | 41, SD and range: NM | 9.5, SD: NM (5–15) | 32 (42) | High, (Sel., Conf.) | Age, BMI, traumatic/non-traumatic, tear type | Lysholm | Higher age and higher BMI: worse outcome (P value NM) Traumatic/non-traumatic, tear type: NS (P value NM) |
| Shelbourne et al, 200634 | Retrospective cohort | Medial, bucket-handle tears | 79 | 29±11 (13–57) | 11.8±6.9 (3–22) | 4 (5) | High (Sel., Conf.) | Age | IKDC | Age: NS (R2=−0.33) |
| Sihvonen et al 20136 | Prospective randomised controlled trial | Medial, all tears | 146 | 52±7 (range NM) | 1 | 57 (39) | Low | Traumatic/non-traumatic | Lysholm, WOMET | Traumatic/non-traumatic: NS (P value NM) |
| Yilar et al, 201424 | Retrospective cohort | Medial and lateral, all tears | 90 | 58±9 (38–82) | 12, SD and range: NM | 64 (71) | High, (Sel., Conf.) | Age, sex, BMI (BMI <25/25–29/>29) | Lysholm, WOMAC | Higher BMI (>29): worse outcome (P<0.0001) Age, sex: NS (P value NM) |
NS, no statistically significant difference found; NM, not mentioned; Sel., selection bias; Conf., confounding; IKDC, International Knee Documentation Committee; KOOS, Knee injury and Osteoarthritis Outcome Score; VAS, Visual Analogue Scale; HSS Knee Score, Hospital for Special Surgery Knee Score; SF-36, Short Form health survey; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; WOMET, Western Ontario Meniscal Evaluation Tool.