An abesss is a region of localised infection, which could result from spread through blood or extension from surrounding areas. The sclerotic region may be due to a past or recent abscess. Well, without knowing the relevant clinical details or a detailed clinical evaluation it would be difficult to comment specifically on the situation. I would suggest getting this evaluated by an internist and an orthopedician. After the relevant clinical details are evaluated for, a management plan can be suggested accordingly.
Hope this is helpful.