Q: I'm 34-years-old, in great shape, and training for our local marathon. But everytime I go out running, I get a feeling of weakness in my right leg after about 25 or 30 minutes. There's pain but it's fairly mild. It seems to be getting worse slowly over time. I don't remember injuring anything. I'm worried I might have pulled a hamstring muscle. How can I tell for sure?

A: Hamstring injuries are usually sudden and acute with a known event or injury. A slow, gradual onset of symptoms such as you describe might be coming from something else. In order to make a decision about the best treatment approach, you may want to see your primary care physician or an orthopedic surgeon. He or she will perform various clinical tests and possibly order imaging studies. X-rays, ultrasound, and MRIs often offer the best diagnostic information with hamstring injuries (or to rule out other possibilities).

The approach to treatment of acute hamstring tendon/muscle injuries depends on the type and extent of injury. A strain or sprain is different from a full or even partial rupture. Sometimes the tendon pulls away from the bone where it attaches, taking a piece of the bone with it. These are called avulsion injuries and may require surgery.

Bleeding into and around the muscle is common with avulsion injuries. Pressure on the sciatic nerve from blood in the area can cause a tingling sensation along the back of the thigh. You didn't mention other symptoms such as numbness or tingling down the leg.

Mild strains or hamstring tendinopathy often respond to conservative (nonoperative) care. Tendinopathy refers to a chronic injury with reactive edema (swelling), thickening of the tissue, and scarring but no active inflammation. Care is usually provided by a physiotherapist who will focus on posture, alignment, core strengthening, and soft tissue mobilization. When appropriate hamstring stretching and strengthening may be included in the program.

When preparing for an event like a full marathon, it's always wise to listen to your body and find out what's causing the painful symptoms. Early intervention may prevent a worsening of the problem and get you back in full training once again.

Reference: Marc Sherry, PT, DPT, LAT, CSCS. Evaluation and Treatment of Acute Hamstring Strains and Related Injuries. In Sports Health. March/April 2012. Vol. 4. No. 2. Pp. 107-114.