Objective: To estimate the genetic contribution to traumatic and degenerative meniscus tears for men and women across the lifespan. Methods: We linked the Swedish Twin Register with individual-level national healthcare data to form a 30-year, population-wide, longitudinal twin cohort. To study genetic contribution to meniscus tears, we estimated the heritability and familial risk using incident traumatic and degenerative tear diagnostic codes in a cohort of 88,414 monozygotic and dizygotic twin-pairs, aged ≥17 years. Results: During follow-up, 3,372 (3.8%) of 88,414 twins were diagnosed with a traumatic or degenerative meniscus tear. The heritability was 0.39 (95% CI = 0.32–0.47) for men and 0.43 (95% CI = 0.36–0.50) for women, and did not vary by age. Environmental factors that were unique to each twin in a pair explained a greater proportion of the variance than genetic factors, both for men (0.61, 95% CI = 0.53–0.68) and women (0.57, 95% CI = 0.50–0.64). Separate analyses of traumatic vs degenerative meniscus tears yielded similar results. Conclusion: For the first time, we have estimated the genetic contribution to doctor-diagnosed meniscus tears using a twin study design. We found a relatively low to modest heritability for meniscus tears (∼40%). The heritability was also fairly stable over the lifespan, and equal in both men and women. Our findings suggest that environmental risk factors are a more important contributor to both traumatic and degenerative doctor-diagnosed meniscus tears than genetic factors.