The musculoskeletal system

Rickets
Fractures; Muscle weakness; bone pain, especially hips
Inadequate calcium or vitamin D so poor calcium absorption into fully-grown bones
Low bone density in spongy and compact bone
Fractures; Poor muscle tone; Loose joints
Mutation affecting collagen structure
Lateral spine curvature
Muscle imbalance so differential pull on spine; some genetic component
Osteoarthritis
Articular cartilage degrades faster than it is rebuilt; no genetic link; not auto-immune
Inflamed, painful joints
Flat foot
Pain in feet, legs, hips, back
Feet do not meet when knees touch
Rickets; bone infection; overweight; injury

Condition	Symptoms	Cause
	Bone pain; Fractures; Knock-knees; Bow legs; Skeletal deformities	Inadequate calcium or vitamin D so poor calcium absorption into growing bones
Osteomalacia
Osteoporosis	Fractures
Brittle bone disease
Scoliosis
	Stiff, painful joints;
Rheumatoid arthritis		Autoimmune condition with environmental influence
		Arch of foot fallen so overpronation strains muscles and ligaments
Knock knees