Swan neck deformity is often seen in patients with rheumatoid arthritis. This is a state in which the distal interphalangeal joint (DIP) becomes hyperflexed (bends toward the palm) while the proximal interphalangeal joint (PIP) is hyperextended (bending away from the palm). Shepherd's crook deformity is seen in Paget's disease of the bone, pencil-in-cup deformity is seen in psoriatic arthritis, and Heberden nodes are frequently seen in the distal phalanges of patients with osteoarthritis.

Duchenne's is the most common and most severe form of muscular dystrophy, accounting for a full 50% of cases of muscular dystrophy in the US. The next most common type is Becker's, followed by myotonic muscular dystrophy and Emery-Dreifuss.

Lambert-Eaton syndrome is a condition of progressive muscle weakness caused by an auto antibodies to presynaptic calcium channels in the neuromuscular junction. This does not allow calcium to enter the presynaptic cell, which is required for neurotransmitter release into the synaptic cleft. Without the release of neurotransmitter, there will be no muscular response. Myasthenia gravis is an autoimmune condition in which antibodies are formed against acetylcholine receptors, and muscular weakness in multiple sclerosis is caused by destruction of myelin in the CNS due to antibodies against oligodendrocytes. Dermatomyositis is an inflammatory connective tissue condition that may be associated with a post-viral autoimmune reaction or triggered by a paraneoplastic syndrome. 

Histological findings of dermatomyositis will generally reveal mixed B cell and T cell perivascular inflammatory infiltrate and perifascicular muscle fiber atrophy.

Fibrosed muscle fibers and fatty infiltrates are typical of Duchenne's muscular dystrophy, while granulomas in muscle are rare but may be seen in sarcoidosis and other conditions of granulomatous myositis.

A rhabdomyoma is a benign tumors of striated muscle. 90% of adult rhabdomyomas present as round masses in the neck. 

A periorbital heliotrope rash is often seen in dermatomyositis. It is bilateral, symmetric, purpuric, and macular, and erupts over the eyelids and surrounding periorbital area. Malar rash (often called a "butterfly rash") is seen in patients with systemic lupus erythematosus (SLE). Dermatitis herpetiformis is a rash on the elbows and knees generally seen with gluten allergy (celiac disease). Perioral dermatitis is an iatrogenic condition often associated with prolonged use of topical steroid creams. 

Polymyositis is characterized by symmetric proximal muscle weakness in the upper and lower extremities, often without the presence of distal muscle weakness. The first sign is often weakness in the thighs while walking, the inability to rise from a seated position without assistance, or the inability to raise the arms above the head. 

Dermatomyositis generally includes a characteristic periorbital rash. Weakness is expressed in the neck, arms, and legs. Guillain-Barre syndrome is an ascending paralysis: symptoms start in the hands and feet, then spread proximally as it progresses. Muscular weakness in myasthenia gravis is often especially expressed in muscles of the face and head, especially those that control eye and eyelid movement, facial expression, chewing, swallowing, and speaking.

Paget's disease of bone is a condition characterized by high bone turnover due to accelerated osteoclast and osteoblast activity. This results in increased calcification of bones, especially prominent in the skull, pelvis, femur, and tibia. 

Osteogenesis imperfecta is an issue with collagen formation that causes fragile bones and multiple fractures. Multiple myeloma is a malignancy of plasma calls, and giant cell tumors are rare tumors that generally originate from the epiphysis of long bones (with no effect on bone deposition).

Paget's disease of the bone generally presents in after the age of 55, and is very rare in younger individuals. The prevalence in individuals over 55 is as high as 3%.

Osteoid osteoma is a benign, bone-forming tumor characterized by a small area of neoplastic growth surrounded by an area of mature, reactive bone.

Fibrosarcoma, osteosarcoma, and Ewing's sarcoma are all malignancies.