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 incomplete healing.

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 also suppress inflammation and provide only temporary relief for a chronic condition, prolotherapy injections given over the course of several 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.

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 Health.

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.