(RECONSTRUCTION OF LAX LIGAMENTS)
THE KNEE BONE CONNECTED TO THE THIGH BONE… NOW HEAR THE WORD OF THE
Ligaments are plastic, semi elastic, cable-like structures made up of
interwoven “collagen” threads connecting bone to bone to form joints. All joints are structured this way: the knee, shoulder, back
and neck, wherever. Ligaments bend, but do not really stretch very well. They have within them nerve endings capable of transmitting
pain impulses. These nerve endings are sensitive to stretching, tearing, pressure, etc. For example, when you sprain your ankle, one
or more of those ligaments may be injured. The injury consists of tearing of the ligaments, the extent varying from microscopic fraying
of a few fibers to total disruption. The ankle then swells, the ligaments are further distracted, stimulating the pain receptors and
producing inflammatory changes as described below. The same mechanism will occur with shoulder injuries, particularly those
related to swimming and pitching and with knee injuries. Subsequently, in order to protect the injured joint, the surrounding
musculature goes into spasm, perpetuating the injury by restricting motion in an aberrant arrangement, impairing circulation, movement,
and resulting in pain. In the instance of the lower back and sacroiliac joints, poor
posture, injuries and shrinkage of the discs (and of the vertebrae themselves) as we age cause these ligaments to be stretched and weak.
They fail to provide adequate support to the joints. Among other things including destabilization of the vertebral column, this allows
the sacrum between the pelvic (iliac) bones to become relatively displaced horizontally and locked in a non-physiologic relationship
with the pelvic bones on each side. Movement is either restricted or excessive and always painful. The surrounding muscles contract,
locking the sacroiliac and vertebral joints and causing more pain, in turn, further restriction of motion, spasm, PAIN.
HEALING AND INFLAMMATION
The body heals ligamentous tears through a process called "inflammation". This process is characterized by redness,
swelling, heat, tenderness, and stiffness of the involved joint. Inflammation takes place in three overlapping stages:
1. Acute inflammation. (Duration approximately four days) In this
phase, beginning directly at the time of injury, the cells are broken
open and their contents spilled at the site of the tear. Leukocytes,
white blood cells, whose job it is to clean out the injured area, flood the region. Many chemicals
are released which act as messengers, telling other cells what to do. "Macrophages" are attracted to the site, beginning the second,
2. Granulation phase: (duration 10 days to two weeks.) The
macrophages and other white blood cells continue the clean up, digesting the broken down cell parts and secreting enzymes and
hormones. These latter stimulate the growth of new blood vessels and generate the ground substance in which the cells ”float”. They
attract additional types of white blood cells, fibroblasts, to the site of injury. These migrate to the fibro-osseous junction, where
the ligament attaches to the bone, and then through stimulation by the macrophages, make massive amounts of the ligamentous building
blocks: single, long collagen fibers. This leads to the third phase of healing:
3. "Wound contraction": (Duration 3 to 6 Weeks) These new collagen
fibers are organized through a complex process into ligaments, the collagen fibers winding about each other and contracting, expressing
fluid, becoming shorter and tightening the support of the joint. The fibroblasts remain at the injury site after all the other clean-up
cells are reabsorbed, continuing to secrete collagen and strengthening the joint for several months.
When the inflammatory process is successful, the ligaments are
returned to their normal length and strength and the joint to its normal function. Should the injury be too severe, or the disruption
perpetuated by abnormal activity or too much swelling, the ligaments will heal in an elongated, disorganized fashion. The result will be
an excessively mobile joint, poorly supported by its ligaments and now dependent on muscles to maintain stability. Unfortunately, the
principal function of muscles should be joint movement and only incidentally joint stabilization.
TRIGGER POINTS (q.v. www.bonesdoctor.com)
Muscles required to act as support structures, are unable to fulfill their obligations as motion agents, since they wind up in a state of
perpetual contraction or spasm. The trigger points (pain receptors) in the now
"stretched" ligaments, are sensitized. This is further complicated by the sensitization of trigger points in the tightened
muscles, setting up myofascial pain syndromes, often referring pain to more distant sites and locally resulting in more muscle spasm,
restriction of motion and pain.
What's the solution? Exercise won't do it. You can’t strengthen a
muscle whose contractions are inhibited by pain. Ligaments will not strengthen or tighten with exercise. Medication won't do it.
Repeated osteopathic or chiropractic manipulations not only won’t help, but may be a perpetuating factor of
ligamentous laxity contributing to joint instability. Surgery may do it in certain cases, but this is obviously fraught with its own
dangers and risks, both immediate and long-range. In fact, the only rational answer is:
As we have seen, a significant proportion of back and joint pain is caused by chronic ligamentous laxity. This is a result of the failure
of the body’s effort to heal the torn ligaments through inflammation. Ligament injection therapy simply stimulates a controlled, gentler
inflammatory process. This involves the deposition of natural chemical and physical irritants at the bony connection of ligaments,
to stimulate their repair. In my practice, I use dextrose (sugar), glycerine, lidocaine (a local anaesthetic, commonly employed in
dentistry),a small amount of phenol (as a chemical irritant, anaesthetic and antiinfective agent). Occasionally this is
supplemented by an infinitesimal amount of an extract of cod liver oil, sodium morrhuate. This stimulates the local production of
prostaglandins, the messengers of inflammation, which draw to the site the agents we discussed earlier. Although the process is
artificially stimulated, it is entirely natural. Prolotherapy can be useful in the treatment of ligamentous laxity in joints other then
the sacroiliac, such as the vertebral joints in all parts of the spine, the hip, knee, foot, ankle, shoulder, elbow, wrist.
Following injection, there is normally swelling, heat, redness, tenderness and pain. This tells us that the inflammatory process we
have deliberately induced is under way. The pain will gradually, but irregularly decrease, and as it does, normal movement and activity
can safely be progressively resumed to tolerance. Normal movement will further enhance the laying down of collagen into ligamentous
fibers. These injections are repeated as necessary, depending on the healing progress, every 3 to 6 weeks, (or even more frequently in
some cases) until such time as the subjective and objective indications for them no longer pertain. That is, pain and function
have normalized to the point that the patient feels he has achieved a satisfactory level of stability, and the physician no longer detects
the objective signs of instability and joint dysfunction. In my experience, this end-point has been reached in as few as one
treatment session and as many as 18.
Although you will be asked to sign a standard informed consent form, the true risks are relatively minor. The injection may be a bit more
painful than anticipated, but after all, the intent of the technique is to create an inflammatory reaction which is characterized normally
by pain, swelling and redness.
This reaction usually does not last for more than 3 to 7 days, and
most frequently is over after two days. Local infection is another possibility, but I have never seen that and the reports in the
literature of same are very scanty. The phenol in the solution acts to sterilize the injection site. Very occasionally there may be some
temporary bruising of a nerve, but I have never seen any permanent adverse consequences as a result. There have been no reports of any
deaths directly related to prolotherapy in the last 25 years, during which time the number of prolotherapy treatments administered around
the world has increased exponentially as has the number of people benefiting from this procedure.
In summary, prolotherapy is a minimally invasive technique utilizing
the injection of, for the most part, organic substances into the site of the junction between ligaments and bones, thereby stimulating
growth and tensile strength. With care in selection of subjects, and administration by well-trained, knowledgeable physicians, the
treatment, although painful, is highly successful, safe and effective in relieving pain due to abnormal joint movement secondary to
HOW WOULD I KNOW IF PROLOTHERAPY
CAN HELP ME?
"I can't sit or stand in any one
position for any significant period without pain. Movies, sports events,
theater, museums, standing on line -- I have to keep shifting, changing
position. Sometimes I feel a "slipped clutch" in my lower back and I am
afraid it will give way. On occasion my leg buckles, I have to support
myself to keep from falling. The pain sometimes radiates down the back of my
These complaints have been going on for years. You've had x-rays, MRIs, CT
scans. You've consulted neurologists, neurosurgeons, orthopedic surgeons,
physiatrists, physical therapists, even psychiatrists. You have had physical
therapy, injections, exercises, medication, osteopathic or chiropractic
manipulation, massage, acupuncture. You may have had epidural steroid
injections and nerve blocks. You may even have had disc surgery. Nothing has
worked if at all, for very long. Pain keeps returning, often at more
frequent intervals, increasing severity, lasting longer, with less
provocation and fewer and shorter pain-free intervals.
Or maybe it's not your lower back. Maybe it's your neck or your shoulder.
You keep getting pain in your neck, shoulder and in your upper back. Your
arm feels heavy, weak. Sometimes the pain radiates downward into your arm
and forearm and even into your hand. Sometimes it's associated with "pins
and needles" sensations. Or, your knee aches and occasionally buckles. You
turn your ankle frequently. What's the solution? You can't strengthen the
muscles as contractions are inhibited by pain. Ligaments will not strengthen
or tighten with exercise. Medication won't do it. Repeated osteopathic or
chiropractic manipulation not only won't help but may be a source of
perpetuating ligamentous laxity contributing to joint instability. Surgery
not only is rarely indicated, but is also obviously fraught with its own
dangers and risks, both immediate and long range. Essentially, if
ligamentous laxity and consequent joint instability is the cause there are
literally only two choices: 1. Live with it and continue to waste time and
money with "Band-Aid" treatments which fail to address the real cause and
may even be perpetuating the problem. Or, 2, the only rational answer:
Ligaments are cable like structures which hold your bones together and allow
you to walk and move without falling apart. Ligaments are flexible, plastic
but they do not stretch very well, not elastic. Injuries such as when you
sprain an ankle, twisted knee, take a bad fall, suffer a "whiplash", or lift
an object which is too heavy may tear or fray these cable like structures.
Ligaments and tendons have within them nerve endings (sensitive to
stretching, tearing, pressure, twisting, chemical changes,) capable of
transmitting pain impulses. These injuries set up a healing process called
inflammation designed to repair the injured ligament (s). You know this
process is happening when you feel the pain and heat, note swelling and have
difficulty moving the injured joint. If the healing process is completely
successful then the ligaments will return to their normal strength and
length and you can resume your usual activities. If it doesn't work
completely, the ligaments may heal in an elongated state. This "stretched
-out" ligament will lead to a situation which can cause pain and discomfort
with movement: joint instability. Subsequently, in order to protect the
injured joint, the surrounding musculature goes into spasm, paradoxically
perpetuating the injury by locking the joint or joints in aberrant
alignment, impairing circulation, movement, and causing pain. In the case of
the lower back and sacroiliac joints, poor posture, injuries, even those
perceived as minor, age-related shrinkage of the discs and vertebra cause
the ligaments to become lax and weak.
When a ligament is strained or injured, some of the strands or threads which
make up the cable become overstretched and broken. (figure 1). Loose
ligaments allow the joint to move beyond its normal range of motion. The
abnormal motion allowed by the strained ligament will produce sensations
ranging from pain to "numbness and tingling", and to referred pain. The
latter is created by the same ligament laxity around the joint but is felt
at some distance from the injured joint. The abnormal joint movement also
creates many protective actions by adjacent tissues. Muscles will contract
in an attempt to pull a joint back to the correct location or stabilize it
to protect it from further damage. We then feel muscle tightness or even
spasm related to the ligamentous laxity. There is a tendency to treat the
muscle spasm as the primary cause of the problem and many medical treatments
may be directed toward this rather than to the primary cause: Ligamentous
strain. If the joint is subluxed or "slightly out of place" because of the
ligamentous laxity, it may respond to manipulation which will often give
good temporary and sometimes permanent relief.
If lax ligaments can lead to muscle spasm, loss of movement, and all sorts
of painful sensations and feelings, what can be done? The only nonsurgical,
minimally invasive treatment for ligament strain or laxity problem is
PROLOTHERAPY. In order to understand Prolotherapy one must understand how
the body heals ligament damage normally. This healing process is called
INFLAMMATION-HEALING THE BODY
There are 3 distinct but overlapping phases to inflammation: Acute,
granulation, remodeling. This "healing cascade" is basic to all injuries
regardless of the site or tissue. These 3 phases each have their own
cellular and chemical processes and changes. Each phase is dependent upon
the previous phase for initiation of the next step. Understanding
inflammation is key to gaining an insight into how Prolotherapy works. The
information below applies both to ligaments and to tendons. For the sake of
simplicity, we will use the term "ligament" for both entities.
The first phase is ACUTE INFLAMMATION and is about 100 hours long. This step
begins at the time of the injury when the ligament and the adjacent cells
are broken open and their contents spill at the wound site. The ligamentous
and cellular debris and a number of chemicals in the fluid or plasma around
the broken-open cells attract an influx of white blood cells called
leukocytes. Their job is to clean out the bacteria and prevent infection at
the injury site. Many of the chemicals released during this phase will be
broken down into messages or chemical signals that tell cells to become
active or inactive . Some of these chemicals are called prostaglandins which
can cause pain at the injury site. More about them later.
The leukocytes also secrete hormones which attract an important cell called
the "macrophage". The arrival of the macrophages at the injury site signals
the beginning of the next phase in the healing process, the GRANULATION
PHASE. As the macrophages arrive at the injury site, they begin to clean up
the area through a combination of digesting the broken down cell parts and
secreting enzymes which break down many of the damaged ligament molecules.
The macrophages also release a number of hormones which will bring more
reparative cells to the injury site. The macrophages also release chemicals
(growth factors) which stimulate the growth of new blood vessels,
intracellular matrix, and the cells that will make new ligaments. These
specialized cells which make ligaments are called fibroblasts. They are
responsible for the actual repairing of a sprained (frayed, torn) ligament.
The combination of all of these cells and the new blood vessels being formed
causes the thickness and fullness that can be felt at the injury site. The
granulation phase will be present for 10 days to two weeks. Fibroblasts will
find the site where the ligamentous structures attached to the bone: The
fibro-osseous junction. Fibroblasts will be stimulated or "turned on" to
make new ligaments by chemicals and hormones that have been released by the
incoming macrophages. When the fibroblasts are turned on, they rapidly make
massive amounts of the basic building blocks of ligaments, collagen.
The third phase of healing is called "REMODELING" or "WOUND CONTRACTION".
During this phase the new collagen deposited at the site of injury will be
organized into a new ligament. The fibroblasts make single long molecules
which, when outside the cell, will begin to entwine around each other,
forming what we call a collagen fiber which is a "triple helix" of these
molecules. The individual molecules are held together by strong chemical
bonds. As collagen fibers wind around each other they begin to contract and
the molecules become shorter and tighter. Water is squeezed out of them
causing further shrinkage. As the millions of collagen fibers lose water and
shrink, the ends of the damaged ligament will be slowly pulled together and
laxity is decreased. We can see this in the healing of a skin wound as the
edges of the wound pull tightly together near the end of the healing
process. During the third phase of the healing process, all of the cells
originally present to "clean up" the wound or recalled by the body. All that
is left are the fibroblasts which have been turned on and are secreting the
collagen and other substances which will be used to increase the integrity
of the injury site. The third phase of inflammation lasts for a number of
weeks and the new ligament tissue will not reach its maximum strength for
several months. Repeated injections during that interval will complement and
enhance the process.
LIGAMENT INJECTION THERAPY
Ligament injection therapy simply stimulates this healing process in a more
controlled, less violent way than occurs following trauma: automobile
accident, slip and fall, twist or athletic injury. Inflammation is created
and collagen generated by the injection of "proliferants". These are nothing
more than irritants. These irritants break open the surface of the cell
walls and allow the spilling out of their contents into the immediate and
adjacent tissue spaces near where the fibroblasts reside: at the connection
of the ligament to the bone, the fibro-osseous junction, the site of most
ligament and tendon injuries,. This then stimulates the healing cascade. A
number of different proliferants may be used capable of initiating this
process: The most commonly used in this office are "osmotic shock agents".
These are dehydrating agents which remove fluids from the cells around the
injection site. Most frequently, I use a solution of 10-15% dextrose in 0.5%
lidocaine. Less often, I may inject a solution of glucose, glycerin, and a
small amount of phenol (P2G) ,.
These solutions may be supplemented by
sodium morrhuate, an extract of cod liver oil. (This is the same long fat
molecule that makes up the cell wall.) When injected in dilute amounts it
stimulates the production of prostaglandins (the chemical messengers of
inflammation). All substances used for Prolotherapy in my practice are
naturally occurring with the exception of the local anesthetic, usually
lidocaine, the same local anesthetic that your dentist might use.
The discomfort of Prolotherapy, because it is an artificial injury is an
important signal that healing is underway. The pain, swelling, heat and
redness caused by the injections are all signs that the underlying cellular
and chemical processes of 200 million years of evolution are safely under
way. The body's pain signals can be listened to and as the pain decreases,
the joint movement can increase.
Why is Prolotherapy needed? If this process is a natural one in the body why
did it not do the job correctly the first time i.e. following injury. We do
not understand all the reasons but some of the more likely causes are:
continued joint displacement following the initial injury the ligament
healing in the "longest possible length" position; the nutrition of the
patient during healing was inadequate; the genetic tendencies to heal are
not complete; or that the healing process itself was suppressed by such
medications as aspirin and other nonsteroidal anti-inflammatories, including
ibuprofen, naproxen, etc. which interfere with the prostaglandin-growth
factor pathways, directly inhibiting the healing of injured ligaments.
Prolotherapy is not a new technique. Prolotherapy was first used by
Hippocrates on Olympic javelin throwers who frequently dislocated their
shoulders. It was used in treating hernias before modern surgical techniques
became available. The techniques and injectants I use are refinements of
those developed in the 1930s by DOs and MDs. Prolotherapy has come a long
way since and is now gaining wider acceptance for painful musculoskeletal
and ligamentous problems and has demonstrated long-lasting results.
Prolotherapy is not entirely without risk. The pain due to the injection
will gradually but irregularly diminish, usually within 2-3 days, and as it
does, normal activity can be progressively resumed to tolerance. Normal
movement will further enhance the laying down of collagen into ligamentous
fibers. These injections are repeated as necessary, depending on the healing
progress, every 2-6 weeks until such time as the subjective and objective
indications for them no longer pertain-that is, pain and function have
normalized to the point that the patient feels he has achieved a
satisfactory level of stability and the physician no longer detects the
objective signs of instability and joint dysfunction.
The injection itself may be painful to varying degrees since the needle is
placed at the fibro-osseous junction, a tender site, the source of the
injury. Local infection is a possibility but has seldom been seen, and I
have never encountered same. Very rarely, injections in the lower back and
neck region may be complicated by puncture of the membrane (dura) lining the
spinal canal and sheathing the spinal nerves. The result may be a so-called
"spinal headache" a painful but self-limiting and benign problem. There have
been no deaths reported connected with Prolotherapy in over 65 years, and
the single case prior to that time was the result of the injection of a
solution that is no longer in use, nor, as a matter of fact, in existence.
Injections to Kick-Start Tissue
The human body is held together by a
network of connective tissues that are highly vulnerable to injury — through
exercise, accidents and even the normal lifting, pulling and pushing of
Few of us, for example, get through
life without spraining an ankle. And as many sadly know, once an ankle is
badly sprained, it may be sprained again and again. That often happens as
well with other body parts: shoulders, wrists, neck, back, jaw, feet, even
fingers and toes, all of which are subject to arthritic changes after an
The risk of reinjury rises when the
ligaments that hold bone to bone, or the tendons that connect bone to
muscle, fail to heal completely. And such failure is apparently very common.
Over time, and with multiple injuries, this incomplete healing can result in
lax connective tissues that cannot fully support a joint.
Dr. K. Dean Reeves, clinical associate
professor of physical medicine and rehabilitation at the University of
Kansas Medical Center, likens the damage to a partly shredded rope that
lacks the strength of an intact one, and to stretched putty that will not
return to its former length. (physical therapists and chiropractors are not
permitted by licensure to provide any therapy requiring injection) . Dr.
Reeves is one of several hundred Allopathic and osteopathic physicians who
specialize in a therapeutic technique called prolotherapy, an alternative
medicine method to promote connective tissue repair even years after the
The technique received an endorsement
of sorts from the Mayo Clinic. In its April 2005 health letter, the clinic
stated that when chronic ligament or tendon pain fails to respond to more
conservative treatments like physical therapy, osteopathic and chiropractic
manipulation, trigger point injections and prescribed exercises,
“prolotherapy may be helpful.” And when surgery is the only remaining option
to relieve chronic pain, prolotherapy is a much less invasive and expensive
technique that may be worth a try — if you can find an experienced and
What Is Prolotherapy?
Prolotherapy involves a series of injections designed to produce
inflammation in the injured tissue. To appreciate the value of such a
seemingly counterproductive measure, you need to know something about
connective tissue and how the body normally repairs it.
When tissues are injured, inflammation
is a common natural response. It stimulates substances carried in blood that
produce growth factors in the injured area to promote healing. Ligaments,
tendons and cartilage have very poor blood supplies, which can result in
The healing process can also be
impeded when injuries are treated with anti-inflammatory medications like
ibuprofen or Naprosyn, or prescribed nonsteroidal anti-inflammatory drugs (NSAIDs)
to relieve pain and swelling.
Unlike injections of corticosteroids, which will suppress inflammation but
provide only temporary relief for a chronic condition, prolotherapy
injections given over the course of several weeks or months are meant to
provide a permanent benefit. In effect, prolotherapy tricks the body into
initiating a healing response.
The technique reactivates the healing
process by injecting a mildly irritating substance — commonly a somewhat
concentrated sugar solution along with the painkiller lidocaine — into the
injured area to stimulate a temporary low-grade inflammation. In some cases,
growth factors themselves may be injected.
With growth factors in place at the
site of inflammation, new tissue is said to be produced that strengthens lax
or unstable ligaments and tendons. The technique may even support damaged or
degenerated cartilage, which normally does not repair itself, by
strengthening the fibrous connective tissues that stabilize the area.
Practitioners cite experiments in
laboratory animals that demonstrated tissue growth in ligaments and tendons
stimulated by prolotherapy injections. Two animal studies also showed
healing of cartilage defects.
Prolotherapy cannot correct mechanical
problems like spinal stenosis, in which two bones pinch a nerve, nor does it
reverse arthritic changes. But it may reduce or even eliminate the
discomfort associated with arthritis by tightening the connective tissues
that support an arthritic joint.
A leader in the field, Dr. Donna
Alderman, an osteopathic physician who is medical director of the Hemwall
Family Medical Centers in California, published two long articles on
prolotherapy this year in the magazine Practical Pain Management. She wrote
that “prolotherapy has been used in the United States for musculoskeletal
pain since the 1930s,” that it has been endorsed by former Surgeon General
C. Everett Koop, and that it is increasingly being used to treat injuries in
Prolotherapy is also now the subject
of a controlled clinical trial sponsored by the National Center for
Complementary and Alternative Medicine, part of the National Institutes of
Since prolotherapy is a nonsurgical
technique, patients who are now facing surgery because all else has failed
might consider trying it before having an operation. Unlike many drugs and
surgery, prolotherapy has minimal side effects when performed by an
experienced practitioner who uses sterile techniques. Patients may
experience bruising and a temporary increase in pain in the injected area
because of the induced inflammation. Rare risks include infection, headache,
nerve irritation or allergic reaction.
Does It Help?
There have been dozens of studies purporting to show benefits of
prolotherapy for people with chronic pain as well as those with sports
injuries. Among scientifically designed controlled studies, most showed a
significant improvement in the patients’ level of pain and ability to move
the painful joint.
According to Dr. Alderman, in a study
of people with chronic low back pain resulting from injured ligaments in the
sacroiliac joint, biopsies done three months after treatment showed a 60
percent increase in the diameter of connective tissue. The patients reported
a decrease in pain and an increased range of motion.
In studies of knee injuries, patients
with ligament laxity and instability experienced a tightening of those
ligaments, including the often disabling anterior cruciate ligament in the
center of the knee, Dr. Reeves showed in a double-blind study. Other studies
showed a significant improvement in the symptoms of arthritis in the knee
one to three years after prolotherapy injections.
Dr. Alderman cautions that
prolotherapy is appropriate principally for patients with musculoskeletal
pain who do not have underlying conditions that would interfere with healing
and who are willing to receive painful injections in an effort to recover.
A state-by-state listing of
prolotherapy practitioners can be found at several websites, including most
prominently, the site of the American Association of Orthopaedic Medicine:
Beware of practitioners who make rash
promises, fail to take a full medical history and to tell you about the
technique and its side effects, or who work in a disorderly or unclean
Should you be interested in further information, many patients have
completed the procedure successfully and would be glad to talk to you about it. Just call my office, say you're interested, leave your
name and phone number and I’ll have them get in touch with you. For more, see the following websites:
These sites are, like the material you have just read, for
educational and informational purposes only and should not be regarded or interpreted as anything else. Diagnosis and treatment of
disease, injury, pain or disability is the province of your health professional who should be consulted in regard to medical symptoms or
conditions before adopting any course suggested in these or any other websites.
to Michele Fecteau, D.O.and Tom Ravin, M.D. upon whose monograph, written
for the American Association of Orthopedic Medicine, I have based much of