Torn muscles and tendons
As discussed above, a torn tendon can be the end results of an untreated tendonitis. However, in some cases a healthy tendon may also suddenly break or even tear of the bone, without any warning, in the middle of a very heavy workout. This usually occurs during extreme heavy lifting or by really jerking the weight up in an uncontrolled manner. The latter can also cause the muscle itself to tear partly or completely. A torn muscle or tendon is usually quite painful, and you immediately feel that you lose any power in the concerned muscle. You may also notice blood accumulation at the location of the tear. Torn muscles and tendons need to be fixed surgically.
Strains and sprains
A strain, also known as a pulled muscle, is an injury in which a few muscle fibers are torn as a result of overstretching the muscle. The equivalent injury to a ligament (fibrous tissue connecting two bones) is a sprain. Typical symptoms of a strain include localized pain, swelling, stiffness, inflammation, and bruising around the strained muscle or ligament. Strains and sprains do not often occur to bodybuilders because they are mainly the result of sudden, unexpected, unnatural, or extreme movements. Strains and sprains almost always heal completely by themselves after a few days or weeks of rest.
Joint or cartilage damage
If you don't perform you repetitions in a controlled way, and let the weight bounce at the bottom of your reps, or allow an overextension of your joints, you will very likely sooner or later be suffering from joint or cartilage damage. Usually the damage is the results of long term incorrect use of your joints. However, it may also be the result of one very wrong movement, especially when you make uncontrolled, jerking movements with very heavy weights. Damaged joints or cartilage usually results in unstable and painful joints, especially during exercise. The damaged tissue can cause a local inflammation and water accumulation within the joint. Joint or cartilage damage is usually permanent.