Muscle, Tendon or Ligament???

[WV Jaz]

Ran my dog yesterday and she ran solid for about 45 min before the rabbit went to hole. Problem later in the evening with her front leg. She started limping and wouldn't put her foot down. I checked her pad, no problem. Felt her leg, no heat, no swelling but she jerked back every time I touched the foreleg. I put Absorbine Jr. on it, thinking it might be a pulled muscle. Today she's putting weight on it but goes easy on it. Still no swelling or heat, but she's still touchy with it. This is a dog that will allow me to do about anything I want to with her since she's in the house full time. So I know if she's touchy with her leg, she's hurting.

When she was a pup occasionally she seemed to have the same type of issue with that leg, but then over the past 10 months or so hasn't had any problems. She isn't over weight and is in great shape. She's generally run about 3 times a week. If it's a muscle, is there any kind of physical therapy I can do with her to prevent it from happening in the future? How can I tell if it's a muscle, a tendon or a ligament? Are the symptoms that much different??

Thanks for any help you can give me.