A sudden severe twist can tear the meniscus, usually occurring when the knee is bent with the full body weight on it. There is immediate pain when standing or walking, but maximum swelling may take a day or two to appear. A large tear may get stuck between the bones preventing straightening of the knee. This is known as a 'locked knee'. The meniscus has poor blood supply, so most tears do not heal.
Arthroscopic surgery can provide relief if pain persists.
Arm injuries also occur, 'Skier's thumb' being the most common. This is a ligament injury at the base of the thumb occurring during a fall on an outstretched hand while still holding the pole. A complete tear requires several weeks of casting or bracing and may even need surgery. If not properly treated, thumb grasp and strength is permanently decreased. This injury can be prevented by not wrapping the pole straps around your thumb.