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:
Knee injuries may cause pain, swelling, instability as well as reducing movement, and may make it difficult to walk.
Here, we look at nine of the most common knee injuries, including how they occur, the symptoms for each one and the best knee injury treatment options. The knee ligaments and cartilage are the structures most frequently damaged so we'll start with those.
Ligament injuries are the most common knee injuries in sports and can affect any of the four knee ligaments:
The anterior cruciate ligament and posterior cruciate ligament control the forwards and backwards movement of the knee and are really important for providing stability.
The medial and lateral collateral ligaments provide sideways stability for the knee.
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:
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:
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
One of the most common knee injuries is damage to the knee meniscus.
The knee joint is lined with two types of cartilage, articular cartilage which lines the bones, and then a second special layer of cartilage known as the meniscus. The meniscus works like special cushioning to reduce the force going through the knee bones.
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:
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
Another group of common knee injuries is muscle damage. If the muscles around the knee are suddenly overstretched or overloaded, some or all of the muscle fibers can tear.
These are commonly referred to as muscle strains. Treated correctly, a full recovery is usually made in a few weeks, but if you try to return to strenuous activities too quickly, you are likely to suffer from long term problems.
What is a Quads Strain Injury: Tear to some or all of the muscles fibers in one or more of the quadriceps muscles
Causes: Sports involving sprinting, jumping and kicking, muscle tightness, weakness and fatigue
Symptoms: thigh pain, swelling, bruising, "popping" sensation and difficulty walking, climbing stairs and getting in and out of a chair
Quads Injury Treatment: PRICE, exercises, tubigrip, physical therapy and occasionally surgery. Visit the Pulled Quads section to find out more.
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.
Damage to the patella is one of the less common knee injuries as it takes a great deal of force through the knee to damage the kneecap. As a result, they tend to be more serious knee injuries.
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.
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
Common knee injuries are diagnosed by a combination of your history, physical examination and radiographic scans.
Doctors and physical therapist can diagnose many common knee injuries from what you tell them about how you injured your knee and your symptoms, and what they can see.
In some cases, they may also send you for tests such as an x-ray or MRI scan to look directly at the bone and/or soft tissues.
As well as these nine common knee injuries there are a number of other causes of knee pain which tend to come on gradually rather than suddenly, such as:
If you have a longer term knee condition or have been having knee pain for a while but don’t know what’s wrong, then go to the section devoted to common knee conditions.
Page Last Updated: 10/13/21
Next Review Due: 10/13/23
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1. British Journal of Sports Medicine: Injuries around the knee - Symposium. Sancheti P, Razi M, Ramanathan EBS, et al. December 2010
2. Orthopedic Journal of Sports Medicine: A Nationwide Follow-up Survey on the Effectiveness of an Implemented Neuromuscular Training Program to Reduce Acute Knee Injuries in Soccer Players. Malin Åman M, Larsén K, Forssblad M, Näsmark A, Waldén M, Hägglund M. December 2018
3. Arthritis Research & Therapy Journal: Down on one knee: soft tissue knee injuries across the lifespan. Thorlund J, Culvenor A, Ratzlaff C. December 2014