Weakness in left knee

by phillip
(australia)

After years of trouble free running and cycling I have developed a feeling of weakness in the left leg in the vicinity of the outside of the left knee. I am still able to run at the same speeds as before but after approx 6km I develop a strange sensation of weakness in the left leg. After experiencing this on three successive runs I rested for a week and received a sports massage as well as conducting daily stretches, but on returning to running I have experienced the same sensation.

The feeling is of weakness and there is no pain associated, it just feels weak and forces me to change my gait. I have also been unable to bend the knee fully while stretching as I feel something is going to pop when I go past approx 110 degrees. I have not increased distance or volume of training.