The knee has complex anatomy with dozens of structures connected together. This complexity makes it particularly prone to injuries that could be incapacitating.

In fact, many world-class athletes had to stop competing because of knee injuries. If the injury is not severe enough to cause debilitating symptoms, it will undoubtedly affect your physical performance.

In this article, we will cover the most common knee injuries that affect active adults.

Top knee injuries for active adults

ACL injury

An ACL injury refers to a tear of the anterior cruciate ligament (ACL), which is a ligament that connects the shinbone to the thighbone.

In the United States, ACL injuries affect 1 in 3,000 people.

Risk factors of ACL injuries include:

  • Sudden changes in the direction of motion or acceleration/deceleration)
  • Direct trauma to the knee
  • Overstretching the knee

Besides knee pain, you may experience the following signs and symptoms:

  • Edema (i.e., swelling)
  • Soreness around the knee
  • Discomfort when walking


In severe traumatic events, the bones of the knee can get broken. This risk is even more pronounced in people with osteoporosis – a condition where bone mineral density drastically drops.

What’s more, osteoporosis can cause knee fractures after even minor injuries (e.g., falling, taking a wrong step).

Torn meniscus

The meniscus is a cartilaginous structure that acts as a shock absorber between the thighbone and the shinbone. Sudden twists of the knee can tear the meniscus, which leads to pain.

Knee bursitis

Bursae refer to fluid-filled sacs spread around your articulations. The specific location of these structures is around the areas where tendons, skin, and muscle tissues meet bones.

The main job of bursae is to lubricate the joint and reduce mechanical friction during movement.

When these fluid-filled sacs get inflamed, we call this condition bursitis. As a result, the affected joint develops pain and swelling.

Prepatellar bursitis – this is due to tearing of the kneecap bursae

Causes include:

  • Physical injury
  • Repeated bending of the knee
  • Infections
  • Bleeding inside the bursae

General symptoms of bursitis are:

  • Pain
  • Swelling
  • Redness
  • Thickening of your bursae

Patellar tendinitis

Jumper’s knee is a common musculoskeletal injury that affects around 20% of athletes who perform jumping activities.

This injury occurs when the patellar tendon that connects the patella to the tibia gets irritated with overuse. The medical term used to describe jumper’s knee is patellar tendonitis, which means the inflammation of the patellar tendon.

Usually, this injury affects the region below the patella and causes pain, swelling, and decreased range of motion of the knee.

Less commonly affected sites include the quadriceps tendon above the patella and at the tibial insertion site of the patellar tendon.

Takeaway message

Knee injuries are very common, especially in active adults. However, people following a sedentary lifestyle are prone to other types of knee problems – degenerative types (e.g., osteoarthritis).

Hopefully, we managed to introduce the different types of knee injuries and their causes.

For tailored medical advice, we recommend contacting your primary care physician or orthopedic surgeon.


Here’s to your health!

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Dr. Kevin Crawford

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Disclaimer:  This information is provided as an educational service only, and is not intended as a substitute for medical advice.  Anyone seeking specific medical advice or assistance should consult his or her doctor or orthopedic surgeon.