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

What is a Quads Tendon Rupture: Full or partial tear of the quadriceps tendon that attaches the quadriceps muscles to the kneecap

Causes: Sports injuries, fall, twisting, tendon weakness, underlying medical condition, corticosteroids

Symptoms: immediate pain above kneecap often with audible "pop", limited knee extension, difficulty walking, knee swelling

Quads Tendon Rupture Treatment: Immobilisation, crutches, physical therapy or surgery for a complete tear. Visit the Quads Tendon Rupture section to find out more.

What is a Calf Strain Injury: Tear to some or all of the muscles fibres in one or both of the calf muscles

Causes: Suddenly - sudden acceleration e.g. jumping or sprinting, or gradually - repetitive overuse e.g. running

Symptoms: calf pain, swelling, bruising, difficulty walking, cramp

Calf Injury Treatment: PRICE, exercises, tubigrip, sometimes requires surgery. Visit the Calf Muscle Strain section to find out more.

What is a Knee Dislocation Injury: Knee cap get pushed out of place. This is one of the least common knee injuries

Causes: Usually caused by major, high impact injury e.g. car crash

Symptoms: Deformed leg - won’t be in a straight line. Very painful and swollen. Occasionally you lose feeling below the knee

Knee Dislocation Injury Treatment: Relocation of the bones, exercises, knee brace, may require surgery.  Find out more in the dislocated patella section.

2. Patella Fractures

What is a Patella Fracture: When the kneecap bone breaks into two or more pieces.

Causes: A great force through the front of the knee e.g. falling from a height or impact from a car crash.

Symptoms: Pain and swelling at the front of the knee. Difficulty moving the knee and walking

Kneecap Fracture Treatment: May require surgery, exercises, knee brace and/or cast. Find out more in the kneecap injuries section

To find out more about each of the specific types of knee injury, including simple and effective treatment options for each, choose from the links above.