Human Skeletal System: Bone Structure

• Bones and joints are essential for structure, support, and mobility in the human skeletal system

Bone Anatomy: Macroscopic Structure

• Compact (cortical) bone is the dense, hard outer layer that provides strength and protection
• Spongy (cancellous) bone is the porous, honeycomb-like inner layer that contains bone marrow and reduces weight
• Bone marrow is found in the medullary cavity of long bones and the spaces of spongy bone
• Red marrow produces blood cells via hematopoiesis
• Yellow marrow stores fat for energy reserve
• Periosteum is a fibrous membrane covering the outer bone surface and contains blood vessels, nerves, and cells involved in bone growth/repair
• Endosteum is a thin membrane lining the inner bone surface and contains osteoblasts and osteoclasts involved in bone remodeling

Bone (Microscopic Structure)

• Osteocytes are mature bone cells that maintain the bone matrix, tissue, and regulate mineral balance
• Osteoblasts are bone-forming cells that synthesize and secrete the bone matrix
• Osteoclasts are bone-resorbing cells that break down bone tissue during remodeling
• The osteon (Haversian system) is the structural unit of compact bone, and runs parallel to the bone's long axis

Types of Bones

• Long bones (e.g., femur, humerus) are longer than they are wide, and function as levers for movement
• Short bones (e.g., carpals, tarsals) are cube-shaped, and provide stability and support
• Flat bones (e.g., skull, scapula) are thin and curved, protecting internal organs and providing muscle attachment sites
• Irregular bones (e.g., vertebrae, pelvis) have complex shapes and serve various functions like protection and support
• Sesamoid bones (e.g., patella) are small and round, embedded in tendons to protect them and improve mechanical advantage

Bone Remodeling

• Bones are dynamic tissues that undergo continuous remodeling
• Osteoblasts build new bone
• Osteoclasts break down old or damaged bone
• Bone remodeling repairs micro-damage, maintains bone strength, and regulates calcium levels

Functions of Bones

• Support: bones provide the structural framework and support soft tissues to maintain body shape
• Protection: bones shield vital organs from injury (e.g., skull protects the brain, ribs protect the heart and lungs)
• Movement: bones act as attachment points for muscles via tendons, and function as levers to facilitate movement
• Mineral Storage: bones store calcium and phosphorus, releasing them as needed for various bodily functions
• Blood Cell Production (Hematopoiesis): red bone marrow produces red blood cells, white blood cells, and platelets
• Energy Storage: yellow bone marrow stores fat for energy
• Acid-Base Balance: bones help regulate pH by absorbing or releasing alkaline salts

Common Bone Disorders

• Osteoporosis is the loss of bone density, leading to increased fracture risk
• Fractures are breaks in bone due to trauma or stress
• Osteoarthritis is the degeneration of joint cartilage and underlying bone
• Osteomyelitis is a bone infection caused by bacteria or fungi
• Bone cancer is the abnormal growth of cells within bone tissue

Joint Structure

• Articular cartilage covers the ends of bones in a joint, reducing friction and absorbing shock
• Joint capsule is a fibrous structure surrounding the joint, providing stability and enclosing the joint cavity; the synovial membrane, its inner layer, secretes synovial fluid
• Synovial fluid is a viscous fluid that lubricates the joint, nourishes cartilage, and reduces friction
• Ligaments, are tough, fibrous tissues connecting bones to bones, providing stability and limiting excessive movement
• Tendons, are connective tissues attaching muscles to bones, enabling movement
• Bursae, are small, fluid-filled sacs that reduce friction near joints
• Menisci are fibrocartilage structures in the knee that provide cushioning and improve stability

Classification of Joints (Structural Classifications)

• Joints are classified based on their structure and function
• Fibrous joints are connected by dense connective tissue with little to no movement (e.g., sutures in the skull)
• Cartilaginous joints are connected by cartilage with limited movement (e.g., intervertebral discs, pubic symphysis)
• Synovial joints are the most common and mobile type, characterized by a joint cavity filled with synovial fluid (e.g., knee, shoulder, hip)

Classification of Joints (Functional Classifications)

• Synarthroses: Immovable joints (e.g., skull sutures)
• Amphiarthroses: Slightly movable joints (e.g., intervertebral discs)
• Diarthroses: Freely movable joints (e.g., synovial joints like the elbow or knee)

Types of Synovial Joints

• Hinge joints allow movement in one plane (e.g., elbow, knee)
• Ball-and-socket joints allow rotational movement in multiple planes (e.g., shoulder, hip)
• Pivot joints allow rotational movement around a single axis (e.g., proximal radio-ulnar joint, atlantoaxial joint in the neck)
• Gliding (plane) joints allow sliding or gliding movements (e.g., between carpal bones in the wrist)
• Saddle joints allow movement in two planes (e.g., thumb joint)
• Condyloid (ellipsoid) joints allow movement in two planes but not rotation (e.g., wrist joint)

Joint Disorders

• Osteoarthritis is the degeneration of articular cartilage, leading to bone-on-bone contact
• Rheumatoid arthritis is the inflammation of the synovial membrane, causing joint damage
• Sprains are overstretching or tearing of ligaments
• Bursitis is the inflammation of bursae due to overuse or injury
• Dislocations are bones forced out of their normal position

Osteoarthritis (OA)

• Osteoarthritis (OA) is a degenerative joint condition causing pain, swelling, and stiffness, limiting free movement
• OA affects the entire joint and surrounding tissues, typically affecting knees, hips, spine, and hands
• OA can be classified as primary (most common with risk factors) or secondary (due to pre-existing conditions)

Osteoarthritis: Signs and Symptoms

• Pain during joint use, often easing with rest, but may worsen at night
• Stiffness lasting less than 30 minutes, especially in the morning or after inactivity
• Reduced joint movement
• Swelling around the joint
• Decreased mobility or joint instability

Osteoarthritis: Risk Factors

• Include age, female gender, obesity, anatomical factors, muscle weakness, and joint injury related to occupation/sports
• Primary OA is diagnosed in the absence of predisposing trauma/disease, but with the associated risk factors
• Secondary OA is associated with pre-existing conditions like trauma or injury, congenital joint disorders, inflammatory/infectious arthritis, avascular necrosis, Paget disease, metabolic and genetic disorders

Osteoarthritis: Epidemiology of OA Knee

• 528 million people worldwide were living with OA in 2019, an increase of 113% since 1990
• 73% of OA patients are older than 55, and 60% are female
• The knee is the most frequently affected joint
• 344 million OA sufferers would benefit from rehabilitation, making it the 11th most debilitating disease globally

Osteoarthritis: Rehabilitation

• Management often involves multiple healthcare professionals contributing to a tailored strategy
• Early diagnosis and treatment is important to slow the disease and optimize function
• Strengthening exercises can help muscles and mobility
• Proprioceptive exercises improve dynamic balance
• Assistive technologies can help with independence when movement becomes difficult
• Non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to control pain
• Maintaining a healthy weight, education, and counseling are important for managing symptoms
• Opioid analgesics, glucosamine, and visco-supplementation therapies are not effective, and there is insufficient evidence for stem cell therapy
• Joint replacement surgery can reduce pain, restore movement, and improve the quality of life for those with severely affected joints, and is most performed at the hip and knee

Rheumatoid Arthritis (RA)

• Rheumatoid arthritis (RA) is a chronic autoimmune disease primarily affecting joints
• RA occurs when the immune system attacks its own tissues, causing pain, swelling, stiffness, and loss of function in joints
• RA affects the lining of joints
• RA often occurs symmetrically
• RA often affects joints of the wrists, hands, elbows, shoulders, feet, spine, knees, and jaw

Rheumatoid Arthritis: Risk Factors

• Age: risk increases with older age
• Sex: More common among women
• Family history and genetics: increased risk if a family member has RA
• Smoking: increases risk
• Obesity: can increase risk
• Periodontitis: may be associated with developing RA
• Lung diseases: may be associated with developing RA

Rheumatoid Arthritis: Epidemiology of Rheumatoid Arthritis

• Worldwide distribution with an estimated prevalence of 1 to 2%, with prevalence increases with age
• 18 million people worldwide were living with RA in 2019
• About 70% of people living with RA are women, and 55% are older than 55 years
• 13 million people with RA experience moderate or severe level symptoms that could benefit from rehabilitation

Rheumatoid Arthritis: Rehabilitation

• Early diagnosis and prompt treatment with disease-modifying antirheumatic drugs (DMARDs) are essential to manage inflammation, prevent damage to joints/organs, and lower mortality risk
• Non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids may help with symptoms but do not change the disease course

Rheumatoid Arthritis: Patient Education

• Education includes information on RA and the importance of exercise and a healthy lifestyle
• Barriers to exercise should be acknowledged and addressed such as lack of knowledge, social support, pain, and fatigue

Rheumatoid Arthritis: Exercise and Therapy

• Tailor exercise to preferences, needs, and goals
• Assess current function and compare it to desired outcomes while incorporating strength, flexibility, and cardiovascular elements into a personalized plan
• Energy conservation helps manage fatigue and reduce joint stress

Osteoporosis

• Osteoporosis is a medical condition characterized by the weakening of bones, making them fragile and prone to fractures
• It arises when osteoblast activity falls behind osteoclast activity, leading to decreased bone density and mass

Osteoporosis: Risk Factors

• Often called a "silent disease" because it progresses without symptoms until a fracture
• More common in older adults, especially postmenopausal women, due to declining estrogen levels
• It can also affect men and younger individuals with risk factors like prolonged use of corticosteroids, low calcium intake, vitamin D deficiency, sedentary lifestyle, smoking, and excessive alcohol consumption

Osteoporosis: Epidemiology

• Osteoporosis is a major non-communicable disease and the most common bone disease
• It affects one in three women and one in five men over 50 worldwide
• A clinical consequence is fragility fractures, with an initial fracture being a risk factor for new fractures

Osteoporosis: Future Risk

• Incidence of osteoporosis and related fractures will continue to increase markedly because of rapid population aging and lifestyle changes
• Due to worldwide prevalence, osteoporosis is a serious health concern

Osteoporosis: Signs and Symptoms

• Fractures with minimal trauma is the hallmark sign
• Common fractures in the spine, hips, and wrists
• Minor falls or bumps can cause a fracture
• Vertebral fractures (compression fractures of the spine) cause back pain
• Spine can lose strength and shape over time, leading to height loss
• Stooped posture due to curvature of the spine caused by weakened vertebrae
• Muscle weakness due to the impact on bones and overall body strength
• Slower movement or difficulty walking due to bone or muscle weakness

Osteoporosis: Rehabilitation

• Includes orthopedic rehab, physical and occupational therapy, nutrition counseling, and personalized treatments to manage the condition and enhance the quality of life

Osteoporosis: Physical and Occupational Therapy

• Physical therapy enhances strength, balance, posture, and flexibility through targeted exercises, pain reducing and improving functional abilities
• Occupational therapy helps adapt daily routines and environments to minimize the risk of falls and fractures, recommending home modifications and safe task performance

Osteoporosis: Nutrition and Personalized Treatments

• Nutrition counseling provides guidance on a bone-healthy diet with calcium, vitamin D, and essential nutrients and may address support overall health and optimize treatment effectiveness
• Personalized treatments are tailored interventions based on individual needs with medication management, pain relief, reducing bone loss and fracture risk and symptoms or limitations