The tearing or over-stretching of the anterior cruciate ligament (ACL) of the knee is referred to as an ACL injury. A tear may be partial or complete, and a partial tear anterior cruciate ligament is also sometimes known as a grade 2 sprain (see below).
Such injuries often occur while participating in sports, or activities which involve sudden movements or risk of falling.
Especially when the force is applied suddenly to the knee, or outside of the knee, and especially if the force is a pivoting or twisting, an injury is possible. This may manifest as a popping sound and sudden sharp pain, and the knee may swell. When this occurs you may feel unstable and unable to support much weight on that leg.
The most immediate symptoms of an ACL injury is of course pain, usually followed by some degree of swelling and fluid build-up. The more severe the injury, the more swelling there will be and the faster it will occur. It can take from a couple of hours, to more than a day to fully swell up, and when it does the knee will of course feel weaker. Other symptoms include stiffness, spasms, and a limited range of motion.
There are three bones involved: the thighbone, the shinbone and the kneecap. They are all connected by ligaments.
Collateral ligamnets on the side of the knee, and cruciate ligaments found inside the knee joint. The latter cross over, forming an "X". The ACL in front and the posterior cruciate ligament at the back. The ACL runs though the middle of the knee, in a diagonal direction, and gives stability to the knee's rotation.
Roughly 50% of ACL injuries , including partial tears, also involve injury to other local structures, such as the cartilage or other ligaments. The injuries here are often referred to as "sprains", and are graded on a scale of severity:
This indicates mild damage and that the ligament has been stretched. In this grade, the ligament is still able to stabilise the joint of the knee.
When the ligament has been stretched to the point of looseness, the injury is a grade 2 sprain and is also referred to as a partial tear.
When the ligament has been completely torn, or split into two separate pieces, the joint will be unstable. Most ACL injuries are complete (or nearly complete) tears, and partial tears are in fact rather rare.
The most common and effective treatments involve rest, compression and ice packs or cold presses; especially when the injury is minor. But then if the ligament is completely torn, surgery may be necessary. Some kind of examination will be carried out, perhaps an MRI or X-ray for instance, and also an arthroscopy, which is the use of a flexible viewing tube that goes inside the knee. This will determine the extent of the injury. During the investigation, excess fluid may be drained by the doctor.
Whereas a torn ACL will not heal on its own, a partial tear may not require any surgery. Non-surgical means are especially effective for elderly or sedentary patients. As long as there an overall stability of the knee, there are a range of simple remedial options which can be recommended by your doctor. A brace, for instance, to support the knee. Or crutches, to save the knee from having to bear too much weight.
However the injury is initally treated, the next stage is vital, and this is rehabilitation. This is a daily plan for getting back to daily life, while allowing for the injury and its gradual recovery. A physical therapy program is almost always used to assist with this. Such a program would aim to first restore motion to the knee, and then strengthen the ligament.
Finally, it would aim to allow for a functional return to the patient's specific daily activites, whether they are demanding as with athletes, or less so as with those with more sedentary lifestyles.