A tendon attaches a muscle to the bone and involves movement of the joint. A ligament connects two bones and is involved in the stability of the joint. A strain is defined as a stretched or injured tendon. A sprain is a stretched or injured ligament. Once a body structure is injured, the immune system is stimulated to repair the injured area. Because ligaments and tendons generally have a poor blood supply, incomplete healing is common after injury. (Browner, B. Skeletal Trauma. Philadelphia, PA: W.B. Saunders Company, 1992, 1:87-88.; Deese, J. Compressive neuropathies of the lower extremity. The Journal of Musculoskeletal Medicine. November 1988, p. 68-91.)
This incomplete healing results in decreased strength of the area. The ligaments and tendons are normally taut, strong bands of fibrous or connective tissue but, because of injury, become relaxed and weak. The injured ligament or tendon then becomes the source of chronic pain and weakness for the athlete.
Ligaments and tendons are also more prone to injury because of the natural aging process. The water content in our joints and connective tissues (ligaments and tendons) decreases with age, the articular cartilage (see research paper) (which lines the joints) gets brittle and shrinks.
Cartilage is so vital, especially in weight-bearing joints like the knee, because it causes an even force to be generated at the underlying bone. It also causes the force generated on the bone to be less. When cartilage is degenerated, the force to the bone is greater and uneven and arthritis develops. Since cartilage decreases the force inside the joint, it becomes obvious that as cartilage deteriorates as we age, other structures are going to have to bear this force. Since tendons move the joints and ligaments stabilize the joints, it is primarily these soft tissue structures that are involved. Because ligaments stabilize the joints, a weakening of these structures causes a further force to the bones of the joints. This increased force hastens the arthritic process.
The greatest stresses to the ligaments and tendons are where they attach to the bone, the fibro-osseous junction. The most sensitive structures that produce pain, according to Daniel Kayfetz, M.D., are the periosteum (covering of the bone) and the ligaments. It is important to note that in the scale of pain sensitivity (which part of the body hurts more when injured), Dr. Kayfetz notes that the periosteum ranks first, followed by ligaments, tendons, fascia (the connective tissue that surrounds muscle), and finally muscle. (Kayfetz, D. Occipital-cervical (whiplash) Injuries treated by Prolotherapy. Medical Trial Technique Quarterly, June, 1963, p. 9-29.) articular cartilage contains no sensory nerve endings. If you are told that your cartilage is the cause of your pain, that is not possible and is, actually, quite ridiculous. The cartilage cannot hurt because there are no sensory nerves to sense pain located in the cartilage. If there is cartilage damage, what hurts? The ligaments are typically the structures that hurt. Ligaments are weakest where they attach to bone. The periosteum is the most sensitive area to pain and the ligaments second. It is now easy to understand why this area hurts so much. This is where the Prolotherapy injections occur and thus eliminate the chronic pain of many conditions including arthritis, mechanical low back pain, degenerative disc disease, cartilage injury, and, of course, sports injuries.
Prolotherapy works by stimulating the body’s healing system, a process called inflammation. The technique involves the injection of various solutions that cause a mild inflammatory response that “turns on” the healing process. The growth of new ligament and tendon tissue is then stimulated. These new ligaments and tendons should not be confused with scar tissue, which is a chaotic matrix of collagen. The ligaments and tendons produced after Prolotherapy, appear much the same as normal tissues, except that they are thicker, stronger, and contain fibers of varying thickness, testifying to the new and ongoing creation of collagen tissue.