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04 May 2022

3 common causes of knee injuries & how they happen

symptoms 6 minutes reading time

An overview of the knee

The knee is the largest joint in your body. It’s also pretty susceptible to injury. The knee is made up of 4 parts:

  1. Bones meet to form your knee joint.
  2. Ligaments connect bones to each other.
  3. Articular cartilage lubricates your knee bones.
  4. The meniscus cushions, absorbs shock, and stabilizes the knee joint.

Head over to our knee guide to learn about the anatomy of the knee in greater detail.

Common knee injuries from running

Runner's Knee

The most common running-induced knee injury–formally known as patellofemoral pain syndrome, informally known as “runner’s knee”–is caused by irritation to the cartilage in your knee.1 It causes pain during exercise, long periods of sitting, and squatting, and is known to affect around 30% of regular runners. Runner’s knee pain ranges from mild to moderate and usually radiates around the kneecap or settles behind it. It’s best to rest your knee when dealing with this kind of knee injury. Ice and elevation may also help. If you struggle with chronic runner’s knee, it may also help to incorporate physical therapy and massage into your routine.2

Iliotibial band syndrome

Like runner’s knee, iliotibial (IT) band syndrome is a common injury resulting from overuse of the knees. It’s estimated to affect about 12% of regular runners. With IT band syndrome, your hip-to-knee tendon tightens, irritating your outer knee. Ice, rest, and over-the-counter anti-inflammatory medications can help with pain reduction. IT band syndrome can sometimes be relieved by a change in footwear and running techniques. Physical and manual therapies (e.g. trigger point) can be beneficial, too.

Jumper’s knee

A less common running-induced knee injury is jumper’s knee (technical name: patellar tendonitis). It’s most common in athletic adolescents and young adults. When a tendon becomes overloaded from overuse, it thickens, which causes pain and irritation in the front of the knee. Jumper’s knee pain is most felt during jumping, squatting, or landing. Rest and ice can help relieve pain in the short term, and ongoing treatment with an orthopedic specialist can help prevent future injuries.

Common knee injuries from sports

Athletic movement can be rough on the knees. Sports that utilize skills like cutting, pivoting, jumping, twisting on a planted foot, and tackling (think basketball, football, soccer) are more likely to result in knee injuries.

Generally, RICE (rest, ice, compress, elevate) and physical therapy are the jumping off points for treating sports-related knee injuries, but surgical intervention may be indicated depending on the severity of the tear(s) in the knee. (A small or partial tear is much less likely to require surgery than a full separation tear.) Knee injuries are diagnosed with physical exams and medical imaging tests like X-rays, MRIs, and ultrasounds. Some of the most common sports-related knee injuries are:

Ligament tears

ACL tears. The anterior cruciate ligament (ACL) is one of several ligaments holding your thigh and shin bones together. When the ACL tears or ruptures during dynamic physical activity, an audible pop might be heard or felt as your knee gives out, making weight bearing extremely painful. About 50% of all ACL tears are accompanied by injuries to other parts of the knee. ACL tears do not heal on their own and most require surgery to be restored to their pre-injury state. Female athletes are between five and nine times more likely to blow their ACLs than male athletes.

MCL and LCL tears. The medial and lateral ligaments (MCL and LCL), which run along the outer parts of the knee joint, can tear when contact or impact pushes the knee sideways. A blow coming from the outer part of the knee tends to injure the MCL; impact to the inside of the knee tends to injure the LCL. Pain is usually localized to the site of impact and the knee will likely feel unstable. MCL tears are the most common knee ligament injuries and tend to heal with time, though may require surgical intervention if other knee injuries were sustained simultaneously.

Ligament tears are rated as Grade 1, 2, or 3 sprains.

  • Grade 1 sprains are mild: the ligament was slightly damaged, but can still stabilize the knee relatively well.
  • Grade 2 sprains are moderate: the ligament was stretched significantly and has become loose; it is partially torn.
  • Grade 3 sprains are severe: the ligament was stretched so far it split into 2 pieces. This is known as a complete tear and it fully destabilizes the knee joint.

Meniscal tears

The menisci (there are two of them) are C-shaped pieces of fibrocartilage that cushion and stabilize the knee.3 They absorb shock between your thigh bone and shin bone and help distribute weight evenly between them. No-contact sports injuries from plant-and-twist leg motions frequently cause meniscus tears. This kind of injury typically results in knee swelling, pain, locking, and limited range of motion.

Dislocated kneecaps

Sometimes, a sports collision will force the small, triangular bone in the front of your knee (patella) sideways and out of its vertical joint at the knee groove, often taking down nearby ligaments with it.4 This is known as an acute patellar dislocation. It is painful and is sometimes plainly visible, making the knee look oddly shaped. A dislocated kneecap will cause the joint to swell, lock, and destabilize, and the pain will not subside until the joint has been corrected. It can be popped back in manually and will sometimes correct itself.

Common causes of knee pain without injury


When the cushioning between joints gets damaged, worn down, or thinned out, arthritis results. Because the knee is constantly in use and heavily involved in everyday movement, many different forms of arthritis can impact it–osteoarthritis (wear-and-tear), rheumatoid arthritis (autoimmune), gout (crystal buildup in the joint), and pseudo-gout (crystals in the joint fluid), to name a few.5

Less commonly, septic arthritis occurs when the knee joint becomes infected. It can quickly eat away at knee cartilage. If you have unexplained knee pain coupled with a fever, seek medical attention straight away.

Body weight

Being overweight or obese stresses the knee joints, increasing your risk of knee injuries. Excess body weight also speeds up the process of osteoarthritis, because more force is acting on the knee joint at any given time, even during routine activities like walking the stairs.

Physically demanding jobs

If your job requires you to be on your feet for much of the day, you might be at higher risk for knee degeneration and pain. Osteoarthritis of the knees is common in farming, carpentry, construction work, brick laying, and floor installation.

Loose body

Degeneration of the cartilage or bones can cause a “loose body”, which is when a small fragment of bone breaks off and floats freely within the joint space.

Scheduling your knee scan

Early diagnosis is the best way to manage and treat your knee injury. Head over to scan.com’s scan search tool to find a reputable imaging center today.


  1. templehealth.org: What Are Common Knee Injuries from Running? | Temple Health
  2. orthoinfo.aaos.org: Common Knee Injuries - OrthoInfo - AAOS
  3. hopkinsmedicine.org: Conditions and Diseases | Johns Hopkins Medicine
  4. mayoclinic.org: Knee pain - Symptoms and causes - Mayo Clinic
  5. clevelandclinic.org: https://my.clevelandclinic.org/health/diseases

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