Human Anatomy

The Knee Joint (Articulatio Genus)

Knee Joint Function

The knee is one of the largest and most complex joints in the body. The knee joins the thigh bone (femur) to the shin bone (tibia). The small bone that runs alongside the tibia (fibula) and the kneecap (patella) are the other bones that make the knee joint.


Tendons connect the knee bones to the leg muscles that move the knee joint. Ligaments join the knee bones and provide stability to the knee.

- The anterior cruciate ligament (ACL) prevents the femur from sliding backward on the tibia.

- The posterior cruciate ligament (PCL) prevents the femur from sliding forward on the tibia.

- The medial (MCL) and lateral (LCL) collateral ligaments prevent the femur from sliding side to side.

Two C-shaped pieces of cartilage called the medial and lateral menisci act as shock absorbers between the femur and tibia. Numerous bursae, or synovial-filled sacs help the knee move smoothly.


Common Injuries of the Knee Joint

Patellofemoral syndrome – irritation of the cartilage on the underside of the kneecap causing knee pain

Osteoarthritis – caused by aging and wear and tear of the cartilage. Symptoms include knee pain, stiffness, and swelling

Knee effusion – fluid buildup inside the knee, usually from inflammation

Meniscal tear – damage to a meniscus, the cartilage that cushions the knee, often occurs with twisting the knee

ACL strain or tear – ACL tear results in knee instability and may require surgical repair

PCL strain or tear – can cause pain, swelling and knee instability, less common than ACL tears, with physical therapy usually the treatment option

MCL strain or tear – may cause pain and possible instability to the inner side of the knee

Patellar tendonitis – inflammation of the tendon connecting the kneecap to the shin bone

Knee bursitis – pain, swelling and warmth in any of the bursae of the knee

Rheumatoid arthritis – an autoimmune condition that can cause arthritis in any joint

Gout – a form of arthritis caused by buildup of uric acid crystals in a joint

Knee Treatments

RICE – Rest (or reduction in activity), Ice, Compression (bandage support) and Elevation

Pain medication – OTC and prescription medication

Physical therapy – strengthens the muscles surrounding the knee

Cortisone injection – injecting steroids to reduce pain and swelling

Hyaluronic acid injections – reduces pain and improves synovial fluid to delay the need for knee surgery

Knee surgery – replace or repair torn ligament, remove an injured meniscus or knee replacement

ACL repair – graft to replace the torn ACL

Nutritional supplements – oral administration of hyaluronic acid, chondroitin, glucosamine, and other nutrients to support join health and mobility


The Hip Joint (Articulatio Coxae)

Hip Joint Function

The hip joint is designed to withstand repeated motion. It is a ball-and-socket joint, the body’s largest. The hip is the joint between the femur and acetabulum of the pelvis.


The cup like acetabulum forms at the union of three pelvic bones (ilium, pubis and ischium).

The hip forms the primary connection between the longer limb and the axial skeleton of the trunk. Both the femur and acetabulum joint surfaces are covered with articular cartilage.

The hip has several other important structures:

- The bursa which is a small sac of synovial fluid that cushions and protects the joint

- The hip joint is reinforced by four ligaments, three of which are extracapsular and one intracapsular

- The hip muscles which control three pairs of principal movement directions


Common Injuries of the Hip Joint

Osteoarthritis – degeneration of cartilage causing pain and inflammation

Rheumatoid arthritis – an autoimmune condition that causes arthritis

Hip fracture – due to a fall or injury involving your leg

Dysplasia – occurs in a newborn baby that has a hip that easily dislocates

Femoroacetabular impingement – caused by a lack of fit of the femur to the acetabulum  that leads to early degenerative changes

Hip labral tears – commonly occurring in athletes, the cartilage protecting the joint tears

Hip Treatments

Pain medication – OTC and prescription medication

Ice therapy – apply ice and rest the effected joints

Cortisone injections – injecting steroids to reduce pain

Physical therapy – exercising the joint with low-impact exercises, stretching and resistance training such as swimming

Hip surgery – replace the hip


The Shoulder Joint (Glenohumeral Joint)

Shoulder Joint Function

The shoulder is one of the largest and most complex joints in the body. The shoulder is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade). The shoulder joint is a ball and socket type of joint which allows a range of motions in the shoulder, such as the upward elevation of the arm and its extension, as well as internal and external motion


Other important bones in the shoulder include:

- The acromion which is a boney projection off the scapula

- The clavicle (collarbone) which joins the acromion in the acromioclavicular joint

The shoulder has several other important structures:

- The rotator cuff is a collection of muscles and tendons that surround the shoulder, giving it support and allowing a wide range of motion

- The bursa is a small sac of synovial fluid that cushions and protects the various joints

- The labrum is a cuff of cartilage that forms a cup for the ball-like head of the humerus to fit into

- The humerus fits relatively loosely into the shoulder joint, which gives the shoulder a wide range of motion, but also makes it vulnerable to injury


Common Injuries of the Shoulder Joint

Frozen shoulder – inflammation develops in the shoulder that causes pain and stiffness

Osteoarthritis – the common “wear and tear” arthritis that occurs with aging

Rheumatoid arthritis – a form of arthritis in which the immune system attacks the joints, causing inflammation and pain

Rotator cuff tear – a tear in one of the muscles or tendons surrounding the top of the humerus

Shoulder impingement – the acromion presses on the rotator cuff as the arm is lifted

Shoulder dislocation – the humerus or one of the other bones in the shoulder slips out of position

Shoulder tendonitis – inflammation of one of the tendons in the shoulder’s rotator cuff

Shoulder bursitis – inflammation of the bursa sac of synovial fluid in the joints

Labral tear – a tear in the labrum of the cuff of cartilage that overlies the head of the humerus

Shoulder Treatments

Physical therapy – an exercise program can strengthen shoulder muscle and improve flexibility

Pain relievers – OTC medications or prescription medications

RICE therapy – Rest, Ice, Compression, and Elevation

Corticosteroid injections – reduce the pain and inflammation caused by bursitis or arthritis

Nutritional Supplements – can assist to restore function

Shoulder surgery – generally performed to help make the shoulder joint more stable


The Vertebral Column Joints

Vertebral Column Function

The spinal column (or vertebral column) extends from the skull to the pelvis and is comprised of 33 individual vertebrae. The vertebral column is the central axis of the body, acting as a support for the weight of the body above the pelvis, encloses and protects the spinal cord and has roles in both posture and movement.


The spinal column can be separated into five different regions, with each region characterized by a different vertebral structure, cervical, thoracic, lumbar, sacrum, and coccyx.

- 7 cervical vertebra with C1 and C2 designed to allow head movement

- 12 thoracic vertebra, medium size and increasing in size moving down the back. Main function is to articulate with ribs

- 5 lumbar vertebra, largest of the vertebra, act to support the weight of the upper body

- 5 sacrum (fused) vertebra articulates with the pelvis

- 4 coccyx (fused) vertebra, small bone which articulates with the apex of the sacrum. Does not contain the spinal cord

Adjacent vertebrae are connected by three intervertebral connections

- Synovial joints formed between the joints

- Specialized cartilaginous joints known as intervertebral discs

- 3 ligaments

The spinal cord lies within the vertebral canal of the vertebra and is covered by three membranes.

Each vertebra consists of a centrum mounted upon a y-shaped neural arch which provides areas of attachment for muscles and ligaments. Together the centrum and neural arch surround the opening through which the spinal cord passes. The centrums are separated by cartilaginous intervertebral discs, which help cushion shock from movement.


Common Injuries of the Vertebral Column

Back Pain – can be acute (lasting days to weeks) or chronic (lasting more than 3 months). This can be due to muscular or ligament strains or due to herniated discs

Herniated Discs – soft tissue in the discs between the joints comes out causing pain by pressing on nerves

Bulging Discs – these protrude but not as much as a herniated disc. Continual symptoms are not experienced, only when the bulging disc pushes on a nerve root

Degenerative Disc Disease – the discs between the vertebra shrink or tear, which causes the bones to rub together

Wear/Inflammation of the sacroiliac joint – where your spine and pelvis meet, swelling and wearing away of the joint cartilage through injury or arthritis

Spinal Stenosis – narrowing of the spinal canal adding pressure to the spine and nerves causing numbness in the legs

Cervical Radiculopathy – a pinched nerve usually caused by a bone spur or a herniated disc

Spondylolisthesis – a bone in the spine slips forward and out of place. The degenerative form is arthritis, which weakens the joints and ligaments keeping the spine aligned

Osteoarthritis – degenerative joint disease which occurs when cartilage breaks down

Scoliosis – curvature of the spine, pain typically starts mid life

Sciatica – acute pain from the sciatic nerve radiating to the buttocks, and sometimes the feet

Vertebral Column Treatments

Rest, Ice and Exercise – reduce pain and inflammation

Physical Therapy – may include massage, ultrasound, whirlpool baths, controlled applications of heat, and exercise programs to help regain full use of the back, strengthening both the abdominal and back muscles helps stabilize the spine

Chiropractor – realign spine

Inversion Therapy – reduce pressure on the discs

Pain medication – OTC and prescription medication

Epidural Steroid Injections – pain management and inflammation

Radiofrequency Neurotomy – pain management

Transcutaneous Electrical Nerve Stimulator (TENS) – mild electric current that helps relieve pain

Acupuncture – for chronic lower back pain

Surgical procedures – to correct disc problems, bone spurs and spinal canal narrowing

• Discectomy – removal of herniated portion of the disc

• Laminectomy – removal of bone to enlarge spinal canal

• Fusion – permanently connects two or more bones in the spine to add stability

• Artificial discs – implanted artificial disc to rep replace a degenerated disc

The Wrist, Hand and Finger Joints

  • The hand and the wrist are made up of 27 bones. The wrist is formed where the two bones of the forearm (the radius and ulna) meet the carpus (wrist). The wrist is made up of multiple joints to allow movement where the bones and the hand meet. The carpus is formed of eight small bones, the carpal bones, which are bound in two groups of four bones.
  • The other bones of the hands are the metacarpals, the five bones that comprise the middle part of the hand and phalanges, the 14 narrow bones that make up the fingers of each hand (each finger has 3: the distal, middle, and proximal) and the thumb has two. 


  • The surfaces of the bones where they meet to form joints are covered with a layer of cartilage, the joints are enclosed by a fibrous capsule that is lined with a thin membrane called the synovium, which secretes synovial fluid to lubricate the joints.
  • The hands and wrist have several other important structures:
  • Ligaments – tough bands of connecting tissue that connect the bones to support them and keep them in place
  • Tendons – bands of connecting tissue that attach the muscles to the bone enabling the muscles to move the bones
  • Nerves – the median, radial and ulnar nerves run the length of the arm through the wrist and into the hand to give sensations of touch, feel of heat and pain


Common Injuries of the Hand and Wrist

  • Osteoarthritis – age related to wear and tear which can also cause deformity
  • Rheumatoid arthritis – an autoimmune condition
  • Carpal tunnel syndrome – compression of a nerve as it goes through the wrist
  • Tendonitis – irritation of the tendons
  • Fractures and dislocations – both fingers and wrists
  • Ruptured ligaments – both fingers and wrists
  • Dupuytren’s contracture – the fixed contracture of the fingers in the flexed position with nodes in the palm

Hand Treatments

  • Pain Medication – OTC and prescription analgesics and injections of steroids
  • Rest, Ice, Heat – relieve pain and inflammation
  • Physical Therapy – including ultrasound and stretching exercises to improve mobility and relieve symptoms
  • Enzyme Injections – to break up tough tissue in dupuytren’s contracture
  • Surgery – required to repair or reconstruct ligaments and in some cases correct carpal tunnel syndrome and dupuytren’s contracture


The Elbow Joint (Articulatio Cubiti)

Elbow Joint Function

The elbow joint is the synovial hinge joint between the humerus in the upper arm and the radius and ulna of the forearm which allows the hand to be moved toward and away from the body. The bone ends are covered with cartilage that allows the joints to slide easily against one another and absorb shock.


Ligaments hold the bones together to form the joint capsule, a synovial fluid filled sac that surrounds and lubricates the joint.

Tendons connect the elbow bones to the arm muscles

- The important ligaments of the elbow are the medial collateral ligament (on the inside of the elbow) and the lateral collateral ligament (on the outside of the elbow) that provide the main source of stability for the elbow.

- The triceps tendon attaches the triceps muscle on the back of the arm to the ulna

- The biceps tendon attaches the bicep muscle on the front of the arm to the radius

- Muscles from the forearm cross the elbow and attach to the humerus, on the outside of the arm just above the elbow with the lateral epicondyle and the inside of the arm just above the elbow with the medial epicondyle (most of the muscles that straighten the fingers and wrist). These are important tendons because they are common locations of tendonitis.

Common Injuries of the Elbow Joint

Elbow contractures (elbow stiffness) – commonly result from trauma/injury, often with ligament damage or fractures, limiting elbow movement and causing pain

Loose Bodies – fragments of bone and/or cartilage that break free within the joint, causing pain, popping and clicking and sometimes locking

Arthritis – primarily osteoarthritis leading to cartilage thinning and bone spur formation, which grow and begin to block movement leading to stiffness and pain

Lateral Epicondylitis (tennis elbow) – painful tendonitis of the group of muscles on the outer part of the elbow

Medial Epicondylitis (golfers elbow) - painful tendonitis of the group of muscles on the inside of the elbow

Osteochondritis Dissecans (OCD) – lack of blood supply to a region of the humerus bone called the capitellum

Dislocated Elbow – when one of the bones that forms the elbow gets knocked out of place

Strains and Sprains – stretching or tearing muscles (strain) and ligaments (sprain)

Bursitis – swelling of the synovial fluid sacs often caused by repeating the same motion

Elbow Treatments

Rest and Ice – reduce pain and inflammation

Physiotherapy – help build strength, improve flexibility and prevent recurrence

Epicondylitis clasps – particularly useful for tennis elbow

Steroid Injections – reduce the pain and inflammation caused by arthritis, tennis elbow, or bursitis

Platelet-Rich Plasma Injections – to accelerate the healing, reduce pain and increase function in tennis elbow

Pain medication – OTC and prescription medication

Elbow Surgery – arthroscopic procedures to remove fragments or repair ligaments or tendons

Nutritional supplements – oral administration of joint supplements including hyaluronic acid and chondroitin 

Muscle – Energy Systems

Muscle Function

Muscles use the stored chemical energy from food we eat and convert that to heat and energy of motion (kinetic energy). Energy is required to enable growth and repair of tissue, to maintain body temperature and to fuel physical activity. Energy comes from foods rich in carbohydrate, protein and fat.

The source of energy that is used to power the movement of contraction in working muscles is adenosine triphosphate (ATP), the body’s biochemical way to store and transport energy. ATP is a high-energy nucleotide which acts as an instant source of energy within the cell. When muscles contract, they break down ATP in a reaction that provides energy. However, muscle cells only store enough ATP to fuel a few seconds of maximal contraction. Once muscle contraction starts, the making of ATP must start quickly.

Since ATP production is so important, muscle cells have several different ways to make it. These systems work together in phases. The three biochemical systems for producing ATP are, in order:

  • Using creatine phosphate
  • Using glycogen (anaerobic glycolysis)
  • Using aerobic respiration

Using Creatine Phosphate

To continue working, muscle cells must replenish their ATP supply. All muscle cells contain a high-energy compound, creatine phosphate, which is quickly broken down to make ATP. Because stores of creatine phosphate are also limited, this energy system can only sustain maximal muscle output for about 10 seconds. The phosphagen system is the primary energy source during very short, rapid bursts of activity, such as sprints.


Using Glycogen (Anaerobic Glycolysis)

To sustain exercise for more than 10 seconds, muscles must break down fuel sources such as carbohydrates and fats to provide the energy to re-synthesize ATP. Carbohydrate metabolism is faster than fat metabolism. Therefore, carbohydrates provide a high percentage of the energy during very high-intensity workouts. Because carbohydrates can be metabolized anaerobically, without oxygen, they become a vital energy source when oxygen supply to muscles cannot keep up with demand.

The breakdown of carbohydrates to provide energy without oxygen is called anaerobic glycolysis. This process releases energy very rapidly and will produce enough energy to last about 90 seconds. It is important that oxygen is not required because it takes the heart and lungs some time to get increased oxygen supply to the muscles. Glucose and stored carbohydrates in the form of glycogen in muscle cells are broken down through a series of reactions to form a compound called pyruvate. This process yields two to three molecules of ATP for each molecule of glucose. A by-product of making ATP without oxygen is lactic acid, which can accumulate in your muscles during rapid exercise causing tiredness and soreness.


Using Aerobic Respiration

Within two minutes of exercise, the body starts to supply working muscles with oxygen. When oxygen is available, pyruvate can be further broken down aerobically to produce as many as 30 additional molecules of ATP, making aerobic metabolism, although slower, much more efficient than anaerobic metabolism. Fats can be broken down aerobically to produce large quantities of ATP. After vigorous workouts, muscles restock ATP supplies aerobically.

Aerobic respiration can supply ATP for several hours or longer as long as a supply of glucose lasts. This glucose can come from several places:

  • Remaining glucose supply in the muscle cells
  • Glucose from food in the intestine
  • Glycogen in the liver
  • Fat reserves in the muscle


Lactate (Lactic Acid) Production

When the body has plenty of oxygen, pyruvate is transferred to an aerobic pathway to be further broken down to ATP (pyruvate is produced by glycolysis from the breakdown of glucose). However, when oxygen is limited, the body temporarily converts pyruvate into lactate, which allows glucose breakdown – and thus energy production – to continue. The working muscle cells can continue this type of anaerobic energy production at high rates for one to three minutes, during which time lactate can accumulate to high levels.

A side effect of high lactate levels is an increase in the acidity of the muscle cells. The same metabolic pathways that permit the breakdown of glucose to energy perform poorly in this acidic environment. This is a natural defense mechanism for the body. It prevents permanent damage during extreme exertion by slowing the key systems needed to maintain muscle contraction. Once the body slows down, oxygen becomes available and lactate is converted back into pyruvate, allowing continued aerobic metabolism and energy for the body’s recovery from the strenuous event.

Lactate buildup is not responsible for the soreness felt in the days following strenuous exercise. Rather, the production of lactate and other metabolites during extreme exertion is the results in a burning sensation often felt in active muscles. This often-painful sensation also gets us to stop overworking the body, thus forcing a recovery period in which the body clears the lactate.