Dogs are more likely to experience limb injuries like sprain muscles, slip discs, teared ligaments or even break bones due to their activity levels. They are always playing, running, jumping or bumping in to things. The most frequent injury is torn knee ligaments.
Also signs of arthritis are shown in senior dogs making them more predisposed to injury of the ligaments. It degenerates the ligament or the disc an can even lead to orthopedic pain or lameness.
Sometimes when injured, limbs may dangle at an unnatural angel or broken bones may even pierce the skin, causing some bleeding and swallowing on the limb.
In any case of limb injury do not try to move the dog. Meanwhile observe his body for any broken bones. Lame dogs should restrict their movements for a few days. If it does not pass than it will need the attention of the vet.
In mild cases just apply cold compress on the effected limb to reduce inflammation. If the inflammation does not go away switch to warm compress.
The cause of a limb can simple be diagnosed with a X-ray. Be careful, do not ever exercise a lame dog. The dog should be able to rest for e few days until he is fully recovered.