There are 3 grades of hamstring strain
Acute Proximal Hamstring Tears Can be Defined Using an Imaged-Based Classification - ScienceDirect
Hamstring Strain - Physiopedia
Hamstring Strain - Physiopedia
What is a hamstring injury, why cricketers are easily prone to one? - Quora
Hamstring Muscle Injuries - OrthoInfo - AAOS
I have strained my hamstrings, when can I return to playing football?
Hamstring Injury: Causes, Symptoms And Treatment
The most common injury in football? ft. Benzema, Kante, Kimpembe and Florenzi
Hamstring injury - NHS
Hamstring Strains