The bone does look like the periosteum is not continuous, but a more experienced expert (an orthopedist perhaps) might be able to provide more precise information about the present condition. My opinion is that a specialist would give provide you with a better answer.

Well I might as well post this here. This is the results of the MRI Scan that was a follow up of the X-ray. Here it goes:
FINDINGS: There is an old fracture of the proximal medial tibia. There is some abnormal extension of the cortical bone medially, which is most likely related to the prior fracture. No impressive features. Some intermediate T2 signal present centerally in the posterior horn of the medial meniscus, but no entension to the articular surface is seen. The lateral meniscus is unremarkable. There is a subcentimeter area of signal abnormality in the distal ACL, which is most likely volume averaging or artifact although could also be a small cyst. The cruciate ligaments, collateral ligaments, and quadriceps mechanism are intact. No focal cartilaginous defect is identified. Some very subtle signal alteration in the lateral patella facet cartilage. Slight increased joint fluid tracking laterally.
IMPRESSION:
1. Healed fracture of the proximal medial tibia.
2. Intrasubstance degeneration posterior horn medial meniscus. No eveidence of meniscal tear.
3. Slight increased joint fluid tracking laterally.

There is is, if anyone wants to point out anything about it, feel free.
Thanks,
Chris

In the photo that you have provided, it appears that the periosteum is not continuous, but a more experienced expert (an orthopedist, perhaps) might be able to tell you more precisely what is happening in the present condition.