Knee sprain
Knee sprains occur when the ligaments that attach the thigh bone (femur) to the shin bone (tibia) tear. The cartilage buffers (meniscus) that act as shock absorbers in the knee can also be injured.
Causes
- Knee injuries are often caused by bending or twisting the knee when the foot is on the ground.
- The knee is often painful and swollen.
- Diagnosis is usually based on the results of a physical examination.
- Rest and immobilisation of the knee is often the only treatment needed, but sometimes serious injuries require surgery.
Several ligaments help hold the knee in place:
Collateral ligaments: these ligaments, located on each side of the knee, prevent the knee from moving too far from one side to the other. The medial collateral ligament is on the inside of the leg, and the lateral collateral ligament is on the outside of the leg.
Cruciate ligaments: these ligaments prevent the knee from moving too far forward or backward. The anterior cruciate ligament (ACL) crosses in front of the posterior cruciate ligament (PCL) to form an X shape.
Cartilage buffers (meniscus) fill the space between the thigh bone (femur) and shin bone (tibia). They help to stabilise and cushion the knee joint.
The most commonly injured structures in the knee are:
- the medial collateral ligament
- the anterior cruciate ligament
The direction of the force applied to the knee determines which structures will tear:
- Medial collateral and anterior cruciate ligaments: one or both ligaments can tear if the side of the knee is struck when the weight of the foot is firmly on the ground, such as when stopping a tackle in American football. Damage is more likely if the knee is also twisted.
- Lateral collateral and anterior cruciate ligaments: these ligaments can be damaged when the force on the knee is directed outwards. This type of injury can occur when the leg is pushed from the inside.
- Anterior and posterior cruciate ligaments: these ligaments can be damaged when the knee is forcefully extended.
- Meniscus: the meniscus can be damaged when you put your weight on one foot and the knee twists when it is injured.
Symptoms of knee sprains and related injuries
Sometimes you hear or feel a clicking sound in the knee when injury occurs. This clicking or snapping usually indicates that a ligament (usually the anterior cruciate ligament) has torn.
The knee becomes painful, swollen, stiff and sometimes bruised. The location of the pain depends on the structure that is injured. The knee may feel unstable, like it’s going to buckle. Muscle spasms (involuntary contractions of the muscles around the knee) may occur.
The timing and severity of symptoms will depend on the severity of the injury:
- Slight: swelling occurs in the first few hours, but may take more than 24 hours. Pain is usually mild or moderate.
- Moderate: pain is moderate or severe, especially when you move or bend the knee.
- Severe: pain can be severe, moderate or mild, and some people cannot walk without help.
Sometimes a torn meniscus prevents the knee from bending (called locking).
Sometimes the force that causes the ankle to twist also causes the bone to break and/or the tendons of the knee to be damaged (injuries to the extensor mechanism of the knee).
Diagnosis of knee sprains and related injuries
- Medical assessment at a physical and rehabilitation medicine or sports medicine consultation with an orthopaedist or one of our physiatrists.
- X-rays to check for bone fractures
- Sometimes, magnetic resonance imaging
Doctors suspect a knee sprain when patients have typical symptoms (such as swelling) and have suffered an injury likely to cause a sprain.
Stress test
Doctors check for knee ligament damage by moving the leg in certain ways (orthopaedic testing). Careful examination, including stress testing and isokinetic testing, usually allows doctors to identify knee injuries.
However, the stress test is usually postponed because the knee is usually too painful to be examined when the doctor first sees the patient. Also, significant swelling and muscle spasms can make it difficult to assess the knee. The stress test can be done a few days later, when the symptoms have subsided.
Treatment of knee sprains and related injuries
If there is a large build-up of fluid in the knee, the doctor will drain the fluid, sometimes at the very first appointment, to help relieve pain and muscle spasms.
The usual treatment is protection, rest, ice, compression and elevation, splinting or knee immobilisation and crutches.
Most mild or moderate injuries can be treated initially with protection, rest, ice, compression and elevation, including immobilisation of the knee with a splint or a device that supports the knee and prevents it from bending (knee brace). Soon after, range of motion exercises are started and progressively increased until the patient has made a full recovery during the physiotherapy sessions.
If the sprain is severe, some people may need to wear a knee brace for six weeks or more.
These injuries are often treated with Platelet-Rich Plasma or other ultrasound-guided procedures. Several studies have evaluated the effectiveness of PRP in reducing inflammation and pain, improving and accelerating the healing process, and increasing mobility and joint and muscle function.
Some serious injuries to ligaments or the meniscus require surgical repair by one of our orthopaedic surgeons. Surgical repair is carried out through a small incision and a small flexible tube – a procedure called arthroscopic surgery.
During physiotherapy, knee strengthening exercising may be recommended for people with mild or moderate injuries. If the injury is severe, strengthening exercises will be delayed until after surgery.
If you need treatment for a knee sprain, contact our physiotherapy clinics in Lisbon.
