Common Knee Injuries

Written By: Chloe Wilson, BSc(Hons) Physiotherapy
Reviewed by: KPE Medical Review Board

Common knee injuries vary from minor falls which may settle quickly to major accidents which may take months to recover from.

Some injuries result from strong forces going through the knee e.g. sporting tackle or fall, whereas others may be the result of simply twisting or bending slightly wrong.

The most common knee injuries fall into four groups:

• Ligament Injuries
• Muscle Injuries
• Kneecap Injuries
• Cartilage Injuries

Knee injuries may cause pain, swelling, instability as well as reducing movement, and may make it difficult to walk.

Knee sprains are one of the most common knee injuries. The term knee sprain refers to the over-stretching of any of the knee ligaments which results in tearing of some of the fibres. 

Knee sprains are usually caused by:

• Sudden force through the knee e.g. sporting tackle
• Sudden twisting e.g. changing direction when running, especially when wearing cleats/stud

Common symptoms of ligament sprains include knee pain, swelling, instability and difficulty bending and straightening the knee.

Find Out More: Knee Sprains - Causes, Symptoms & Treatment

ACL knee injuries are a common problem in sport caused by overstretching of the anterior cruciate ligament in the center of the knee.

The ACL is extremely strong, but if the knee gets bent back too far, or twists awkwardly, then the strain on the ACL can cause some of the fibres to tear, or with enough force, rupture completely. 

People often report a loud popping sound when the ligament tears, similar to a gunshot and there is usually immediate knee pain and swelling. ACL tears often result in long term knee instability, especially with pivoting and twisting movements.

Depending on the severity of damage and the functional demands of the individual, then physical therapy and rehab may be sufficient, but some cases will require surgery. Find out more about the causes, symptoms and treatment options in the ACL Injuries section.

An MCL tear is one of the most common injuries that causes pain on the inner side of the knee. The medial collateral ligament is usually damaged by overstretching from:

• Force through the outside of the knee: e.g. sporting tackle or fall
• Sudden twisting: of the knee e.g. skiing

Typical symptoms of an MCL tear include inner knee pain, swelling, instability and difficulty bending the knee. 

Most MCL tears can be treated at home, but if the ligament has torn completely, then surgery may be necessary.

Find Out More: MCL Injuries - Causes, Symptoms & Treatment

Damage to the posterior cruciate ligament is one of the less common knee injuries, usually caused by a force through the top of the shin bone causing the knee to bend backwards e.g. car accident or fall on to a bent knee.

Unlike other common knee injuries, there may not be much pain at the time of injury and symptoms may take time to develop. Pain and swelling from a pcl injury is usually fairly mild, but there may be ongoing problems with knee instability, particularly with activities when the knee is bent e.g. stairs, problems with running.

Find Out More: PCL Injuries - Causes, Diagnosis & Treatment

A meniscus tear is a tear in the special thick cartilage that lines the knee joint. Meniscus tears usually fall into two categories, those that occur due to:

• Injury: sudden force through the knee or sudden twisting of the knee
• Wear and Tear: gradual degeneration of the cartilage, most typically due to arthritis or a previous injury

Symptoms of meniscus tears usually include knee pain, swelling, locking, instability, difficulty straightening the knee and difficulty walking.

Meniscus tears are notoriously slow to heal due to there being a poor blood supply to the meniscus.

Find Out More: Meniscus Tears - Causes, Symptoms & Treatment

A quads tendon rupture is a serious but less common knee injury where there is a full or partial tear of the quadriceps tendon that attaches the quadriceps muscles to the kneecap

A quads rupture is typically a sporting injuries but can also be caused by a fall, twisting akwardly, tendon weakness, an underlying medical condition or from corticosteroids

Common symptoms of a quads tendon rupture include immediate pain above kneecap often with an audible "pop", limited knee extension, difficulty walking and severe swelling above the knee.

You can find out all about the causes, symptoms, diagnosis and treatment options in the Quads Tendon Rupture section.

Another common knee injury affecting athletes and runners is a calf tear. This is where there is damage to some or all of the muscles fibres in one or both of the calf muscles

Calf tears are one of those knee injuries that can happen suddenly, from sudden acceleration e.g. jumping or sprinting, or may develop gradually, from repetitive overuse e.g. running

Common symptoms include calf pain, swelling, bruising, difficulty walking, and cramp

Find out how to treat and prevent common knee injuries in the calf muscles in the Calf Muscle Strain section.

A dislocated patella is one of the less common knee injuries where the knee cap get pushed out of place. 

It takes a great deal of force to dislocate the kneecap and patellar dislocations are usually caused by a major, high impact injury e.g. car crash

Not only will the knee look deformed/out of place, it will also be extremelt painful and swollen. Occasionally you lose feeling below the knee.

Find out all about the causes, symptoms and treatment options in the dislocated patella section.

2. Patella Fractures

Patella fracture knee injuries occur when the kneecap bone breaks into two or more pieces.

Again, it takes a great force through the front of the knee for the kneecap to break e.g. falling from a height or impact from a car crash, making patella fractures one of the less common knee injuries.

There will be extreme pain and front knee swelling with a patella fracture which will limit knee movement and function.

You can find out more about the causes and treatment options in the common kneecap injuries section.