Dear Marty,  

If you are a runner, you have either had a running related injury, or will have one at some point in the future.  They are almost impossible to avoid completely.  However, there are a few simple steps to minimizing your chances of getting one, as well as steps to rehabilitate if you do get one.

Avoiding injury:
1) Follow an appropriate plan.  This means don't go from not running at all to running 20 miles next weekend.  You need to build up the mileage in a sensible fashion, so that your muscles gain the strength to complete longer and harder distances, AND your tendons, ligaments and bones toughen up and adjust to the strain running causes. This is the biggest risk factor you can control.

2) Engage in strength and conditioning exercises.  This would include stretching as well as supplemental strength exercises. Many of the injuries discussed below are a results of inflexible calf muscles, weak hip and glute muscles, and tight or inflexible muscle fascia.  Most of us are predisposed to weakness in one or more of these areas.

3) Stay light. If you are carrying around extra weight, this places additional strain on your muscles, soft tissues, and cardiovascular system.

4) Run in appropriate footwear. The barefoot running craze is over, but there are still many different types of shoes out there.  Talk to a footwear specialist about what sort of shoe you should be using.

5) Stay hydrated.  Dehydration reduces muscle performance which increases the strain on your soft tissues. 

6) Run on softer surfaces like dirt and rubber tracks. Each step transmits about 3x your bodyweight through each leg every time you run. 

7) Limit running if you detect early signs of injury. No matter how tough you are, pushing through potential running injuries is usually a bad decision.  You can substitute things like elliptical training, water running, and weight-reduced treadmill running.

Some of the most common running injuries are:

Shin splints. Ramping up the mileage, inadequate preparation (didn't run all summer is common), bad shoes, growth spurts, and hard surfaces contribute. Requires ice, compression, rest & rehab to heal. This article from Peak Performance Online is the best one I've found over the years on shin splint rehab and prevention: 

Knee pain / patella tendonitis. Inflammation of the tendon that holds your kneecap in place. Caused by mileage changes, muscle imbalances, growth changes. Rest, ice, rehab.  

Patellofemoral pain syndrome, aka runner's knee.  This is pain in the knee that may have different immediate causes, but frequently damages the cartilage under the kneecap.   Avoid downhill running if you have knee pain.

Muscle strains (or pull) - typically occur in the hip flexor, calf, hamstring, or quadriceps muscles in runners. This is a tearing of your muscle fiber and can be varying degrees of severity. Minor strains require just a bit of rest but major ones require extensive rest and rehab, occasionally surgery. You can help prevent this by staying hydrated, staying on top of your nutrition, and getting your sleep as that is when your body does the majority of repairs.

Ankle sprain/twists - stretching one of the ligaments that supports your ankle. Taking one bad step is all this takes. Can be various grades of severity from mild to severe/complete tear. Ice, elevation, rest, and sometimes total cessation of leg activity. Watch where you run!

Iliotibial band pain - this is a band of tissue called fascia that runs from your hip to your knee. The pain is typically felt at the knee but tightness or glute discomfort may also be felt. 

Achilles tendonitis. Inflammation of the achilles tendon and can turn into the chronic problem below.

Achilles tendinosis. This is degradation of your achilles tendon and is a chronic issue if you don't take action to mitigate and avoid further damage. Strengthening and stretching the calf muscles are critical.

Stress fractures.  This typically occurs when you let your mileage get ahead of your body's ability to adapt to higher training loads and can occur in any of the bones from your hips downward, but is most common in the tibia.  Requires complete cessation of running for at least six to eight weeks.

If you suspect you have a running injury, follow these steps:

1) Discontinue activity that causes pain. Ice the area and take anti-inflammatory over the counter drugs in the near term.

2) Get a professional diagnosis and treatment plan from a PT or sports medicine doctor.  They will proscribe a course of action including a timeline for a return to full running activities. 

3) Follow this plan diligently.  Rehab exercises are usually meant to be followed almost without end.  As you age, your body loses strength and flexibility, so you need to stay on top of these.

4) Run on soft surfaces when possible.  Surfaces like dirt and rubber tracks allow more of the force to transmit to the ground than hard surfaces like cement sidewalks and paved roads. Each step transmits about 3x your bodyweight through each leg every time you run. 

5) Don't give up!  While you may not be cleared to log 50+ mile weeks or do hard track workouts, you can enjoy the runs you can take part in. 

Further reading:

Run workout of the month