Table 2.

Risk of bias assessment of included studies.

Study	Criterion 1	Criterion 2	Criterion 3	Criterion 4	Criterion 5	Criterion 6	Criterion 7	Criterion 8	Criterion 9	Criterion 10	Criterion 11	Criterion 12	Criterion 13	Criterion 14	Overall Risk of Bias
Patellar cartilage volume
Cohort studies
Cicuttini, et al³¹	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	Yes	Yes	NR	Yes	Low
Hanna, et al³³	Yes	Yes	NR	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Low
Antony, et al²⁸	Yes	Yes	NR	No	No	Yes	Yes	Yes	Yes	No	Yes	NR	Yes	Yes	Moderate
Gunardi, et al²⁶	Yes	Yes	No	Yes	No	Yes	Yes	Yes	Yes	No	Yes	NR	NR	Yes	Moderate
Teichtahl, et al³⁶	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	Yes	NR	No	Yes	Moderate
Patellar cartilage defect
Cross-sectional studies
Ding, et al²¹	Yes	Yes	NR	No	No	No	No	Yes	Yes	No	Yes	NR	NA	Yes	High
Duran, et al²²	Yes	Yes	Yes	No	No	No	No	Yes	Yes	No	Yes	NR	NA	Yes	High
Cohort studies
Ding, et al³²	Yes	Yes	NR	No	No	Yes	Yes	Yes	Yes	No	Yes	No	Yes	Yes	High
Wang, et al¹²	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	Yes	Yes	No	Yes	Moderate
Carnes, et al³⁰	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	Yes	NR	Yes	Yes	Moderate
Bucknor, et al²⁹	Yes	Yes	NR	Yes	No	Yes	Yes	NA	Yes	No	Yes	Yes	No	Yes	Moderate
Roemer, et al³⁴	Yes	Yes	No	Yes	No	Yes	No	NA	Yes	No	Yes	Yes	Yes	Yes	Low
Patellar cartilage volume and cartilage defect
Cross-sectional studies
Hanna, et al²³	Yes	Yes	No	Yes	Yes	No	No	Yes	Yes	No	Yes	No	NA	Yes	High
Cohort studies
Teichtahl, et al²⁷	Yes	Yes	NR	Yes	No	Yes	Yes	Yes	Yes	No	Yes	No	NR	Yes	Low
Teichtahl, et al³⁵	Yes	Yes	NR	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Low
Cartilage quality
Cross-sectional studies
Koff, et al²⁴	Yes	Yes	NR	Yes	Yes	No	No	Yes	Yes	No	No	No	NA	No	High
Widmyer, et al²⁵	Yes	No	NR	Yes	No	No	No	NA	Yes	No	Yes	No	NA	No	High

Items included on the risk of bias tool:
1. Was the research question or objective in this paper clearly stated?
2. Was the study population clearly specified and defined?
3. Was the participation rate of eligible persons at least 50%?
4. Were all the subjects selected or recruited from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants?
5. Was a sample size justification, power description, or variance and effect estimates provided?
6. For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured? (For cross-sectional analyses, the answer to Question 6 should be “no.”)
7. Was the time frame sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed? (For cross-sectional analyses, the answer to Question 6 should be “no.”)
8. For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome (e.g., categories of exposure, or exposure measured as continuous variable)? (if binary NA)
9. Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?
10. Was the exposure(s) assessed more than once over time?
11. Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?
12. Were the outcome assessors blinded to the exposure status of participants?
13. Was loss to follow-up after baseline 20% or less?
14. Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?
NR: not reported; NA: not applicable.