ACL reconstruction

I am now 4 weeks post-op having had hamstring graft acl reconstuction. Recovery was going very well until 4 days ago when, whilst stretching my calf muscle I felt a sudden, sharp 'twanging' sensation in the centre of my hamstring, accompanied by intense pain. It soon settled but caused stiffness in my hamstring and the back of my knee. This has happened 5 or 6 times since when stretching my hamstring, and feels as if it could happen again at any time. I am concerned I may have damaged the hamstring muscle or tendon and am unsure whether I should continue exercising it. Obviously I will speak to my physio about it but I'm still waiting on a referal from a different hospital. If anyone has had a similar experience or knows what I may have done please let me know.

You may have been doing too much too soon. Only very light stretching is necessary at that stage, and even then any loading of the hamstrings in traditional stretching exercises can be too much as it is such a significant stabilizing muscle. It probably is not significant but should be checked.