Certain regions of the body are simply more likely to be painful than others, and the knees are very high on this list. Knee pain ranks behind just back pain as the second most common condition involving the muscles and bones, and in adults aged 65 and older, it is the greatest cause of disability.

The knee is the largest and one of the most complex joints in the body, and this complexity is a main reason why it is so vulnerable to injury. The nearly constant use of the knee during all standing, walking, and running activities also plays a major role.

The knee is a hinge joint that’s responsible for bearing weight and allowing the leg to extend and bend back and forth with minimal side–to–side motion. It primarily joins the thighbone (femur) to the shinbone (tibia), but also includes the kneecap (patella) and other lower leg bone (fibula). The patella is a small, triangle–shaped bone that sits in the front of the knee within the quadriceps muscle, and it’s lined with the thickest layer of cartilage in the body to protect it from the significant forces of regular movements.

If pain develops in the knee or thigh, you may be unsure what to do next. For mild pain that’s manageable, it’s common—and recommended—to wait a week or two and see if it subsides on its own or after trying some pain–relieving modalities like ice. But for severe knee or thigh pain and pain that persists or gets worse over several weeks, you should seek out help from a medical professional.

Physical therapists are movement experts who can effectively treat most types of knee and thigh pain with a comprehensive treatment approach that focuses on addressing deficits with targeted interventions. Certain causes of knee pain, however, may require the expertise of other healthcare professionals to safely manage. To help you differentiate between the two, below are some of the most common knee diagnoses that physical therapists treat, followed by a few key red flags that suggest an underlying condition is present that requires additional care:

• Knee osteoarthritis: an extremely common disorder in which the cartilage lining the ends of bones in the knee gradually wears away, which reduces its ability to absorb shock, thereby increasing the risk for these bones contacting one another; usually leads to pain, stiffness, and swelling that make it difficult to walk and move the knees normally



• Patellofemoral pain syndrome (runner’s knee): accounts for 16–25% of all running injuries and involves the patella rubbing against the groove of the femur, which causes a dull pain behind or around the patella; this pain is often aggravated by running, squatting, climbing stairs, or sitting, and may also be accompanied by swelling or a “popping” of the patella when bending the knee



• Patellar tendinopathy (jumper’s knee): caused by repetitive strain to the patellar tendon, which attaches the bottom of the patella to the top of the tibia; leads to pain and stiffness at the front or below the patella and/or in the quadriceps, as well as an aching sensation that’s usually brought on after exercise



• ACL tear: the anterior cruciate ligament (ACL), which helps stabilize the upper leg bone to the knee, can be damaged or torn when an athlete suddenly cuts or changes direction; ACL tears are most common in football, basketball, and soccer, and usually sideline athletes for extended periods of time



• Meniscus tear: tears of the meniscus, a tough piece of cartilage that absorbs shock and stabilizes the knee, typically occur from twisting or turning too quickly on a bent knee, often when the foot is planted; degenerative meniscus tears may also occur in older adults; symptoms include pain, swelling, and difficulty extending the knee



• Iliotibial band syndrome: an injury in which the iliotibial band—which runs from the hip to the top of the tibia—becomes irritated or inflamed from rubbing against the patella, leading to pain on the outside of the knee or hip that usually arises after running



• Hamstring strain: the three muscles in the back of the thigh form the hamstring; any of these muscles can be pushed beyond their limits in sports that involve sprinting, running, or lots of stretching; soccer, basketball, tennis, and football are some of the most common culprits



• Quadriceps strain: involves a partial or complete tear of one of the four quadriceps muscles—which are located in the front of the thigh—or their tendons; this injury is common in sports and usually occurs when an athlete is trying to accelerate and the muscles are placed under more force than they can withstand

• Extreme bruising, swelling, or throbbing pain


• Significant bone pain, which may suggest a bone tumor


• Persistent swelling and pain that develops without any recent injury


• Lacerations


• Signs of infection (eg, pus or fluid, redness, fever, blisters, worsening swelling)


• Inability to place any pressure on the injured leg

We hope this guidance helps you determine whether physical therapy is the right call if you’re experiencing knee or thigh pain. In our next post, we provide you with 4 effective exercises you can perform on your own that will help to prevent and treat this type of pain.