Strain: A strain is often referred to as a "pull" and involves the tearing of muscle or tendon fibres, ranging from microscopic damage (grade 1 strain) to complete ruptures (grade 3). The tearing of muscles or tendons is most likely to occur during sudden acceleration or deceleration which is something dogs do a lot of, particularly when chasing an object such as a ball. This can be a debilitating and painful condition commonly resulting in not being diagnosed correctly. Depending on the severity of the strain, the dog may go off their food, experience bruising, inflammation, pain and weakness. Whilst working and sporting dogs are more at risk of a strain, a strain can happen to any dog at any time. Once a muscle has been damaged with a strain it will never be as strong as it was before and can re-strain as a result (known as the strain, re-strain cycle).
Scar Tissue: Scar tissue is the fibrous connective tissue which forms a scar; it can be found on any tissue on the body, including skin and internal organs, where an injury, cut, surgery or disease has taken place and then healed. Thicker than the surrounding tissue, scar tissue is paler and denser because it has a limited blood supply and may contribute to reduced range of movement and circulation. Massage can help to break down scar tissue and help realign the fibres, although it can not be removed completely.
Trigger Point: Trigger points are small, hyper-irritable bands commonly referred to as ‘knots’ found in any skeletal muscle in the body which causes pain when touched as they are usually very tender. In a dog the over contracted muscle will begin to shorten which reduces the range of motion in the muscle and can cause pain, lameness and a change in body posture. This then has a knock-on effect to the rest of the dog's body as other muscles are forced to overcompensate and so become sore and tender to touch and are incredibly painful when gentle pressure is applied. There are many factors which contribute towards trigger points, such as jumping in and out of the car, injury and over-compensation in conditions such as hip dysplasia and arthritis.
Spasm: A spasm is a sudden involuntary contraction of a muscle or group of muscles which have been overworked or over used. As a muscle goes into spasm it will feel very tight and tender to touch. Spasms usually occur due to prolonged uncomfortable activity, muscle weakness or aggravation of an underlying, existing issue causing tightness in muscles. This can result in a dog being unable to move in their normal way due to pain on movement.