Tendons connect muscles to bones; ligaments hold joints together. Both consist of tight bundles of fibres whose blood supply decreases over the course of life. That is why, in middle and older age, they often tear without any major accident – when lifting something heavy, missing a step or making a short sprint.
In the shoulder, the rotator cuff surrounds the head of the humerus: four muscles whose tendons lift and rotate the arm and keep it centred in the joint. Tears here are usually due to wear and tear and almost always occur after the age of 50. Typical signs are pain at night, weakness when lifting the arm and discomfort when working overhead.
The Achilles tendon connects the calf to the heel. In almost all tears, it already shows signs of wear beforehand, and not every tear is recognised straight away – leaving a gap with loss of strength when rolling the foot through a step. In the knee, the anterior cruciate ligament stops the lower leg from sliding forwards. After an old tear, the knee sometimes gives way when turning.
Whether and when to operate also depends on timing: a tendon that has been torn for longer retracts, the associated muscle can waste away, and a repair becomes more difficult. With the cruciate ligament, by contrast, current knowledge suggests there is no disadvantage in starting with non-surgical treatment and deciding later.