question: What's the difference between contortionists and people who have hypermobile joints? Is there a difference?
comment: Contortionists have trained their muscles and body to stretch in all sorts of ways. Those with hypermobile joints have what is basically a birth defect or mutation that lets them be extra flexible. They are physically different from the norm for whatever reason. In gaming terms, Hypermobile Jointed people would be a race that specs well into a Contortionist's career.
passages: Some loose-jointed people are able to pop a joint out of its socket without pain, thereby making it difficult to determine if a joint is dislocated without medical examination such as an X-ray. However, as long as the joint socket is the right shape, most extreme bends can be achieved without dislocating the joint. Actual dislocations are rarely used during athletic contortion acts since they make the joint more unstable and prone to injury, and a dislocated limb cannot lift itself or support any weight.
  
  Section::::List of notable contortionists.
   In the past, contortionists were associated almost exclusively with circuses and fairs, but recently they have also found work performing in nightclubs, amusement parks, in magazine advertisements, at trade shows, on television variety shows, in music videos, and as warmup acts or in the background at music concerts.
   The condition frequently is not noted until late childhood, as function may be normal, especially in unilateral cases. Increased wrist motion may compensate for the absent forearm motion. It has been suggested that individuals whose forearms are fixed in greater amounts of pronation (over 60 degrees) face more problems with function than those with around 20 degrees of fixation. Pain is generally not a problem, unless radial head dislocation should occur.
   BULLET::::- Contortion positions can be performed on a Spanish web, an aerial act consisting of a rope with a hand/foot loop that is spun by someone underneath.
  
  BULLET::::- Contortionists might manipulate props during their performance, for instance spinning hula hoops or juggling rings, balancing towers of wine glasses, or playing a musical instrument.
  
  A contortionist may perform alone, may have one or two assistants, or up to four contortionists may perform together as a group.
   BULLET::::- Spinal muscular atrophy (SMA)
  
  BULLET::::- Arthrogryposis
  
  BULLET::::- Muscular dystrophy (MD)
  
  BULLET::::- Parkinson’s disease
  
  BULLET::::- Hypertonic muscle spasm
  
  BULLET::::- Pierre Robin malformation
  
  Section::::Treatment.
  
  Section::::Treatment.:Types of splints.
  
  There are more than eighty Dynasplint Systems that stretch in extension and flexion of the elbow, wrist, hand, finger, knee, and toes, as well as dorsiflexion and plantarflexion of the foot and ankle, supination and pronation of the forearm, internal rotation and external rotation of the shoulder, as well as abduction and adduction of the fingers and toes. Sizes are available from infant to extra large adult and are individually fit by consultants.
   A medical publication from 2008 suggests that long-term damage to the spine is common in long-term contortion practitioners. A study of five practitioners using magnetic resonance imaging (MRI) by Peoples et al. documented limbus vertebrae, intervertebral disc bulges, and disc degeneration. Three of the five practitioners also reported back pain.
  
  Section::::Performances.
  
  Contortion acts are highly variable; many incorporate elements of humor, drama, shock, sensuality, or a blend of styles. Contortion may be incorporated into other types of performance, such as dance and theater.
   Hypermobility (joints)
  
  Hypermobility, also known as double-jointedness, describes joints that stretch farther than normal. For example, some hypermobile people can bend their thumbs backwards to their wrists, bend their knee joints backwards, put their leg behind the head or perform other contortionist "tricks". It can affect one or more joints throughout the body.
  
  Hypermobile joints are common and occur in about 10 to 25% of the population. It is usually not associated with any symptoms but a minority of people develop other conditions caused by their unstable joints; in such cases, it is known as hypermobility syndrome.
   BULLET::::- Troy James - A contortionist who appeared in season 13 of "America's Got Talent". Troy has also portrayed Rag Doll in "The Flash" and Baba Yaga in "Hellboy.
  
  BULLET::::- Yash Shah - An Indian contortionist who appeared in "India's Got Talent" and can rotate his hands and legs 360 degrees.
  
  BULLET::::- Doug Jones - An actor and creature performer.
  
  BULLET::::- Irina Kazakova - A Russian contortionist and gymnast.
  
  BULLET::::- Jaspreet Singh Kalra - An Indian contortionist who has been nicknamed the "Rubber Man".
   BULLET::::- Placing flat hands on the floor with straight legs
  
  BULLET::::- Left knee bending backward
  
  BULLET::::- Right knee bending backward
  
  BULLET::::- Left elbow bending backward
  
  BULLET::::- Right elbow bending backward
  
  BULLET::::- Left thumb touching the forearm
  
  BULLET::::- Right thumb touching the forearm
  
  BULLET::::- Left little finger bending backward past 90 degrees
  
  BULLET::::- Right little finger bending backward past 90 degrees
  
  Section::::Treatments.
  
  Section::::Treatments.:Physical therapy.
   Limited range of motion can affect extension or flexion. If there is limited range of extension, it is called "Flexion Contracture" or "Flexion Deformity". If the flexion is deficient, it is called "Limited Range of Flexion" or "Limited Flexion Range".
  
  Section::::Limited range of motion.:Range of motion exercises.
  
  Physical and occupational therapy can help to improve joint function by focusing on range of motion exercises. The goal of these exercises is to gently increase range of motion while decreasing pain, swelling, and stiffness. There are three types of range of motion exercises:
   Many factors affect the flexibility of performers including age, genetics, stature, and adherence to rigorous physical training routines. Most contortionists are generally categorized as "frontbenders" or "backbenders", depending on the direction in which their spine is most flexible. Relatively few performers are equally adept at both.
  
  Skills performed by contortionists include:
  
  BULLET::::- Frontbending skills such as folding forward at the waist with the legs straight, or placing one or both legs behind the neck or shoulders with the knees bent (called a human knot).
   "Synergist" muscles perform, or help perform, the same set of joint motion as the agonists. Synergists muscles act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion.
   Most people have hypermobility with no other symptoms. Approximately 5% of the healthy population have one or more hypermobile joints. However, people with "joint hypermobility syndrome" are subject to many difficulties. For example, their joints may be easily injured, be more prone to complete dislocation due to the weakly stabilized joint and they may develop problems from muscle fatigue (as muscles must work harder to compensate for weakness in the ligaments that support the joints). Hypermobility syndrome can lead to chronic pain or even disability in severe cases. Musical instrumentalists with hypermobile fingers may have difficulties when fingers collapse into the finger locking position. Or, conversely, they may display superior abilities due to their increased range of motion for fingering, such as in playing a violin or cello.
   Medication is not the primary treatment for hypermobility, but can be used as an adjunct treatment for related joint pain. NSAIDs are the primary medications of choice. Narcotics are not recommended for primary or long term treatment and are reserved for short term use after acute injury.
  
  Section::::Treatments.:Lifestyle modification.
  
  For some people with hypermobility, lifestyle changes decrease symptom severity. In general, activity that increases pain is to be avoided. For example:
  
  BULLET::::- Typing can reduce pain from writing.
  
  BULLET::::- Voice control software or a more ergonomic keyboard can reduce pain from typing.
   BULLET::::- Enterology is the practice of squeezing one's body into a small, knee-high box or other contained space which initially appears to audiences as being too small to contain the performer.
  
  BULLET::::- Dislocations of the shoulders or hip joints are sometimes performed as a short novelty act by itself. One example is lifting the arm to the side until it passes behind the head and lies across the top of the shoulders; also referred to as bonebreaking.
  
  Section::::Risks.
   Section::::Tension myositis syndrome.
   BULLET::::- The shape of the ends of the bones—Some joints normally have a large range of movement, such as the shoulder and hip. Both are ball and socket joints. If a shallow rather than a deep socket is inherited, a relatively large range of movement will be possible. If the socket is particularly shallow, then the joint may dislocate easily.
   The only movements permitted in the interphalangeal joints are flexion and extension.
  
  BULLET::::- Flexion is more extensive, about 100°, in the PIP joints and slightly more restricted, about 80°, in the DIP joints.
  
  BULLET::::- Extension is limited by the volar and collateral ligaments.
  
  The muscles generating these movements are:
   The Ross Sisters were American contortionists most famous for their musical number in the 1940s movie "Broadway Rhythm". In addition, contortion photos and digital movie clips are traded by fans on the Internet, and several web sites provide original photos of contortion acts for a monthly fee, or sell videotapes of performances through the mail.
   Early models describing the kinematics of an individual target joint during the various phases of manipulation (notably Sandoz 1976) were based on studies that investigated joint cracking in MCP joints. The cracking was elicited by pulling the proximal phalanx away from the metacarpal bone (to separate, or 'gap' the articular surfaces of the MCP joint) with gradually increasing force until a sharp resistance, caused by the cohesive properties of synovial fluid, was met and then broken. These studies were therefore never designed to form models of therapeutic manipulation, and the models formed were erroneous in that they described the target joint as being configured at the end range of a rotation movement, during the orientation phase. The model then predicted that this end range position was maintained during the prethrust phase until the thrust phase where it was moved beyond the 'physiologic barrier' created by synovial fluid resistance; conveniently within the limits of anatomical integrity provided by restraining tissues such as the joint capsule and ligaments. This model still dominates the literature. However, after re-examining the original studies on which the kinematic models of joint manipulation were based, Evans and Breen argued that the optimal prethrust position is actually the equivalent of the neutral zone of the individual joint, which is the motion region of the joint where the passive osteoligamentous stability mechanisms exert little or no influence. This new model predicted that the physiologic barrier is only confronted when the articular surfaces of the joint are separated (gapped, rather than the rolling or sliding that usually occurs during physiological motion), and that it is more mechanically efficient to do this when the joint is near to its neutral configuration.
   BULLET::::- Muscle tone—The tone of muscles is controlled by the nervous system, and influences range of movement. Special techniques can change muscle tone and increase flexibility. Yoga, for example, can help to relax muscles and make the joints more supple. However, please note that Yoga is not recommended by most medical professionals for people with Joint Hypermobility Syndrome, due to the likelihood of damage to the joints. Gymnasts and athletes can sometimes acquire hypermobility in some joints through activity.
  
  BULLET::::- Proprioception—Compromised ability to detect exact joint/body position with closed eyes, may lead to overstretching and hypermobile joints.
   BULLET::::- "Discontinuation of physical treatments -" Sarno advises patients to stop using spinal manipulation, physical therapy and other physical treatments because "they tend to reinforce erroneously a structural causation for the chronic pain."
  
  BULLET::::- "Resumption of normal physical activity -" Schechter states that patients are encouraged to "gradually be more active, and begin to resume a normal life." In addition, patients are encouraged "to discontinue the safety behaviours aimed at protecting their 'damaged' backs".
  
  BULLET::::- Support meetings
   BULLET::::- Morphea profunda involves deep subcutaneous tissue, including fascia, and there is a clinical overlap with eosinophilic fasciitis, eosinophilia-myalgia syndrome, and the Spanish toxic oil syndrome. Morphea profunda shows little response to corticosteroids and tends to run a more chronic debilitating course.
  
  BULLET::::- Pansclerotic morphea is manifested by sclerosis of the dermis, panniculus, fascia, muscle, and at times, the bone, all causing disabling limitation of motion of joints.
   Muscle fibers can only contract up to 40% of their fully stretched length. Thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, and those that act over several joints may be unable to shorten sufficiently to produce the full range of movement at all of them simultaneously (active insufficiency, e.g., the fingers cannot be fully flexed when the wrist is also flexed). Likewise, the opposing muscles may be unable to stretch sufficiently to allow such movement to take place (passive insufficiency). For both these reasons, it is often essential to use other muscles, called fixators or synergists, in this type of action to fix certain of the joints so that others can be moved effectively, e.g., fixation of the wrist during full flexion of the fingers in clenching the fist. Synergists are muscles that facilitate the fixation action.
   In determining a diagnosis between with catatonia, akinetic mutism, and FCMS, a person must demonstrate their ability to perform voluntary function of the limbs. Patients with catatonia or akinetic mutism are not able to perform voluntary commands that involve the use of limbs, while patients with FCMS still possess voluntary usage of limbs. If a person can demonstrate ability in voluntary usage of limbs, catatonia and akinetic mutism are most likely ruled out from the diagnosis.
  