Small intrasubstance signal seen in posterior horn of medial meniscus could be degenerative / grade 1 tear. it is my knee joint mri report. ?

It is a common find.: I assume you are asking is the finding unusual? The answer is the finding is a very common finding, especially in older patients. If you are having knee pain, your physician should do a good physical exam to see if your findings on MRI correlate to the MRI findings. As this interpretation can be an incidental finding, you need to discuss your physical findings together with the report.

Probably nothing: To call a tear, you must see signal going to the edge of the meniscus. Intrasubstance signal not extending to the surface would not satisfy criteria for a tear on mri. As a side note, the quality of the scanner and the scan parameters they chose will have great impact on the ability to see subtle findings such as this.