Disorders of bones: Arthritis and osteoporosis are two diseases of bones in humans. 

(i) Arthritis Inflammation of the joints is the main cause of it. It is of many types like rheumatoid arthritis, osteoarthritis and gouty arthritis. 

(a) The rheumatoid arthritis is diagnosed by the presence of rheumatoid factor. The joints becomes immovable. It is cured by heat treatment and physiotheraphy. 

(b) The osteoarthritis is a degenerative joint disorder. It is characterized by the degeneration of the articular cartilage and proliferation of new bones. 

(c) The gouty arthritis is called gout. This is caused due to excessive formation of uric acid which gets deposited at the joints. 

(ii) Osteoporosis: 

(a) It is age-dependent systemic disorder. 

(b) It is characterized by low bone mass, microarchitectural deterioration of the bone. 

(c) It is also characterized to fracture. 

(d) It can occur in the pregnant women. 

(e) Thyrocalcitonin, parathyroid and sex-hormones imbalance is the main cause of this disease. 

(f) Major causative factors are the deficiency of vitamin D and calcium deficiency in the body.