**Core Concept**
Chronic osteomyelitis is a prolonged infection of the bone, often resulting from inadequate treatment of acute osteomyelitis. This condition can lead to various complications, including the formation of sequestra and amyloidosis. Metastatic abnormality, also known as Garre's sclerosing osteomyelitis, is a rare form of chronic osteomyelitis characterized by periosteal reaction and sclerosis. Myositis ossificans, on the other hand, is a condition of abnormal bone formation within the soft tissues, typically occurring after trauma.

**Why the Correct Answer is Right**
Myositis ossificans is a distinct entity from chronic osteomyelitis, characterized by heterotopic ossification in the muscles and surrounding tissues. This condition is usually seen in the context of trauma or post-surgery, rather than as a complication of chronic osteomyelitis. The pathophysiology of myositis ossificans involves the abnormal differentiation of mesenchymal cells into osteoblasts, leading to the formation of bone within the soft tissues.

**Why Each Wrong Option is Incorrect**
**Option A:** Amyloidosis is indeed associated with chronic osteomyelitis, particularly in cases of long-standing infection. The chronic inflammatory response can lead to the deposition of amyloid proteins in various tissues, including the bones.

**Option B:** Sequestrum is a characteristic feature of chronic osteomyelitis, where a piece of dead bone becomes separated from the surrounding healthy bone tissue. This occurs due to the infection, which causes necrosis of the bone.

**Option C:** Metastatic abnormality, or Garre's sclerosing osteomyelitis, is a rare form of chronic osteomyelitis that is indeed associated with this condition. It presents with periosteal reaction and sclerosis, and is thought to be a result of the body's attempt to contain the infection.

**Clinical Pearl / High-Yield Fact**
When diagnosing chronic osteomyelitis, it's essential to consider the patient's medical history, including any previous episodes of infection or trauma. A thorough physical examination and imaging studies, such as X-rays and MRI, can help identify the characteristic features of chronic osteomyelitis, including sequestra and periosteal reaction.

**✓ Correct Answer: D. Myositis ossificans**