Any weekend athlete knows exercise can put stress on your joints. Thirty- to 50-percent of sports injuries are tendon injuries. In the worst cases those injuries lead to surgery. But now, there's a new procedure that can regenerate tendons that's as simple as a blood draw and injection.

Point guard Nikki Teasley spent six years in the WNBA and almost as long fighting a painful tendon injury in her knee.

"I thought I was going to have to retire, the pain was too, too bad. You get up in the morning, and I couldn't walk because I was in so much pain," Teasley said.

Teasley thought surgery was her only option until doctors suggested something else.

"My terms are they take out the bad and put in the good," Teasley said.

It's called "platelet rich plasma injections." The patient's blood spins in a centrifuge to separate blood platelets from plasma and red blood cells. Then under ultrasound guidance, doctors inject the platelets into the injured part of the tendon.

When the platelets come into contact with the injured tendon, they attract stem cells. These stem cells stimulate healing.

"And they will cause new collagen to form and actually fill in the defect that has been caused by the overuse of the tendon," said Dr. Kenneth Mautner, a sports medicine specialist at the Emory Sports Medicine Center in Atlanta.

"After the injection, I feel like I can play 5 more years," Teasley said.

Teasley's ready for another season, this time focused on scoring points without pain.

The platelet injection procedure generally costs between $750 and $1,500 when it's done in the doctor's office, far less than surgery, which can cost $5,000 to $10,000 or more. It is covered by some insurance carriers. The procedure is intended for patients with tendinosis, which is degeneration of the tendon -- not tendonitis, which is inflammation. People who take long-term aspirin therapy or Plavix aren't candidates for the platelet therapy.

ABOUT TENDON PAIN: Tendons are rope-like structures that connect muscle to bone and enable the bone to move. When a tendon is first injured, it may become inflamed, swollen and painful. Chronic tendon pain is different -- it happens when tissue begins to break down and is not always marked by inflammation. Whereas a tendon injury is referred to as tendinitis, chronic tendon pain is called tendinosis.

Tendinosis -- or tendionopathy -- of the knee occurs when a person puts too much load on the tendon and causes multiple small injuries over time. "We put too much load on the tendon, which it just can’t handle, so the tendon tries to adapt, and tries to heal itself, but over time, it loses the ability to heal itself," Mautner said. As the tendon loses the ability to heal, it degenerates and loses strength.

CAUSES: Doctors say there are many causes for tendinosis of the knee, the most common being overuse of the tendon. Overuse happens when a person puts too much load on the tendon for it to handle. "Doing too much, too soon, too fast, as a lot of our weekend warrior athletes do," Mautner said. Other types of tendinosis can result from extended use of computers, playing musical instruments or doing manual labor. According to Tendinosis.org, some occupations that carry an increased risk for chronic tendon injuries include assembly line workers, mail sorters, computer programmers, data entry processors and cashiers.

TREATMENTS: While in the past doctors recommended more traditional treatment methods like ice, anti-inflammatory medications, steroid injections and physical therapy for tendinosis, those have proven unsuccessful in many cases. Newer treatment options for the condition involve heating, massage and surgery.

A new, surgery-free option for the treatment of tendinosis is called Platelet-Rich Plasma (PRP) Therapy. Designed to initiate the healing process in damaged tendon tissue, the procedure involves drawing a patient's blood, placing it in a centrifuge for 15 minutes and injecting the platelet-rich plasma into the diseased portion of the tendon. During the injection, the doctor is guided by an ultrasound image. After the injection, patients are put on a program of rest followed by physical therapy for six weeks. Some patients require more than one treatment to achieve a successful outcome. The treatment is also being utilized in the treatment of tennis elbow, Achilles tendon injuries and a common running injury called plantar fasciitis.