Table 2

Data extraction of the included prospective and retrospective cohort studies

StudyStudy typeDuration of follow-up (weeks)Participants (total group and cases of AT)Sex (% male)Age, mean±SD (years)Location injuryRisk factors (risk ratio, OR and HR)Quality score (points)
Barge-Caballero et al24RCNR149 (14); heart transplant patients who were prescribed quinolones.77.9%58.8±10.6AT (not specified midportion or insertional).
  • A creatinine clearance <60 mL/min was associated with AT compared with a creatinine clearance ≥60 mL/min (OR 6.14; 95% CI 1.23 to 30.64; p=0.03).

  • Increased time (in years) between heart transplantation and initiation of quinolone treatment for infectious disease was associated with AT (OR 1.39; 95% CI 1.11 to 1.74; p=0.005).

  • No associations were found for age, sex, levofloxacin use and daily prednisone dose (mg).

5
Hein et al20PC52269 (10); recreational runners.NRNRAT (not specified midportion or insertional).
  • No statistical analyses were performed.

4
Kaufman et al21PC104449 (30); Navy Sea, Air and Land (SEAL) candidates.100%22.5±2.5AT (not specified midportion or insertional).
  • A tight ankle dorsiflexion with knee extended (<11.5°) was associated with AT compared with a normal dorsiflexion (11.5–15.0°) (RR 3.57; 95% CI 1.01 to 12.68; p<0.05).

  • No associations were found for hindfoot inversion, hindfoot eversion, static arch index of the foot, dynamic arch index of the foot and dorsiflexion of the ankle with the knee bent.

5
Mahieu et al16PC669 (10); officer cadets.100.0%18.4±1.3Midportion AT.
  • Isokinetic plantar flexion strength at 30°/s was decreased in patients who developed AT for both the right and the left leg and at 120°/s for the right leg (p=0.042, p=0.036 and p=0.029, respectively). Plantar flexion strength was measured using the Cybex Norm dynamometer, which measures strength at constant velocity.

  • No associations were found for weight, BMI, length, physical activity level, Achilles tendon stiffness, isokinetic plantar flexion strength at 120°/s for the left leg, explosive gastrocnemius-soleus muscle strength (standing broad jump test) and passive and active ankle joint range of motion outcomes.

4
Milgrom et al22PC141405 (95); infantry recruits.100.0%18.7±7Midportion AT.
  • An increase in AT was seen when training in the winter season compared with summer training (p=0.001).

  • No differences were found in height, weight, BMI, external rotation of the hip, tibial intercondylar distance, arch type, physical fitness performance (2 km run and maximum number of chin-ups and sit-ups done) and shoe type.

4
Owens et al17PC5280 106 (450); military service members.70.3%NRAT (not specified midportion or insertional).
  • Being overweight and obesity were associated with AT compared with underweight or normal weight (AOR 1.29, 95% CI 1.04 to 1.59 and AOR 1.59, 95% CI 1.16 to 2.17, respectively)

  • A prior lower limb tendinopathy or fracture was associated with AT (AOR 3.87, 95% CI 3.16 to 4.75).

  • Moderate alcohol use (7–13 units per week for men, 4–6 units per week for women) was associated with AT compared with no alcohol use (AOR 1.33, 95% CI 1.00 to 1.76).

  • A birth year of 1980 and later was associated with a decreased risk for AT compared with a birth year before 1960 (AOR 0.62, 95% CI 0.38 to 1.00).

  • No associations were found for sex, ethnicity, smoking status and heavy alcohol use (14+ units per week for men, 7+ units per week for women).

6
Rabin et al18PC2670 (5); military recruits.100.0%19.6±1.0Midportion AT.
  • Every 1° increase in ankle dorsiflexion with the knee bent was associated with a decreased risk for AT (OR 0.77; 95% CI 0.59 to 0.94).

  • No associations were found for BMI and lower extremity quality of movement.

7
Van Ginckel et al19PC10129 (10); novice runners.14.7%39±10Midportion AT.
  • An increased total anterior displacement of the Y-component of the centre of force was associated with a decreased risk for AT (OR 0.919; 95% CI 0.859 to 0.984; p=0.015).

  • A more medial directed force distribution underneath the forefoot at forefoot flat was associated with a decreased risk for AT (OR 0.000; 95% CI 0.000 to 0.158; p=0.016).

  • No associations were found for age, height, weight, BMI or physical activity score.

6
Van der Linden et al25RCNR10 800 (8); patients using fluoroquinolones (index group) or amoxicillin, trimethoprim, cotrimoxazole or nitrofurantoin (reference group).29.8%46.3 (SD NR)AT (not specified midportion or insertional).
  • The use of ofloxacin was associated with AT compared with the reference group (AOR 10.1; 95% CI 2.20 to 46.04).

  • No associations were found for fluoroquinolones as a group, ciprofloxacin use and norfloxacin use compared with the reference group.

3
Wezenbeek et al23PC104300 (27); first-year students.47%18.0±0.8Midportion AT.
  • Female sex was associated with AT (HR 2.82, 95% CI 1.16 to 6.87).

  • Height and body weight were increased in patients with AT (p=0.028 and p=0.015).

  • No association was found for a pronated foot posture.

  • No differences were found for BMI, rating of perceived exertion, hours of sports participation and leg dominance.

7
  • AOR, adjusted OR; AT, Achilles tendinopathy; BMI, body mass index; NR, not reported; PC, prospective cohort study; RC, retrospective cohort study; RR, risk ratio.