Knee Common Conditions


The knee is a large, complex joint that is very commonly injured. During activity, it is subject to tremendous force. When injuries arise, your best pathway to recovery is a team of highly-trained professionals that understands your injury and knows how to treat it. At Boston Orthopaedic & Spine, our board-certified, fellowship-trained specialists have the skill and expertise to treat all of your knee concerns.

Knee Anatomy

The knee is the body’s largest joint, and the place where the femur, tibia, and patella meet to form a hinge-like joint. These bones are supported by a large complex of muscles, tendons, ligaments, and cartilage which allow the knee joint to function.

  • Knee moves like a hinge, but it can also rotate and move from side to side.
  • Patella is held in place by tendons and ligaments. The patellar cartilage is the thickest in the body.
  • Knee Ligaments (ACL, PCL, MCL, LCL) hold the knee joint in proper position. When one or more are injured, the knee is subject to instability.
  • Menisci are cushions of tissue (cartilage) that increase the contact area of the knee. Injury to the menisci commonly cause locking, catching, and pain.
  • Cartilage covers the ends of the bone and provides a cushion and healthy local environment

Symptoms of knee pain

Symptoms of knee pain depends on the type of injury and mechanism of injury. In many cases, there is no definite starting point for the pain, which also helps up determine a diagnosis. The symptoms commonly include pain with walking, pain when using stairs, instability when changing directions, swelling, stiffness, popping and catching.

We can generally diagnosis the source of your knee pain with a good history, physical exam, and xrays. In some cases, advanced imaging such as an MRI is useful to confirm our suspicions and identify other issues that may be hidden.

Common causes of knee pain treated at Boston Orthopaedic & Spine

Anterior cruciate ligament (ACL) injuries

The ACL is one of the ligaments in the knee joint that connects the thighbone (femur) with the shin bone (tibia). Injuries to the ACL are generally associated with a specific injury event. Symptoms of an ACL injury include pain and swelling on the outside and back of the knee, and instability or limited movement in the knee joint. Treatment depends on many factors by may include physical therapy, bracing, and in some cases, surgery.


Arthritis is painful inflammation and stiffness of the joints, which can be caused by many types of degenerative or inflammatory conditions. There are many types of arthritis, including osteoarthritis, rheumatoid, post-traumatic, septic, and gout. Arthritis symptoms often include swelling, tenderness, sharp pain, stiffness, and sometimes fever and chills.

Knee arthritis is one of the most common disabling locations for arthritis. It is managed initially with activity modifications, gait aids such as a cane, stretching and strengthening exercises to build up the supportive musculature, anti-inflammatory medications, Tylenol, and injections. When these options fail to provide relief, surgery may be indicated.


Bursitis is painful inflammation of the bursae, the fluid-filled sacs that reduce friction between bones, tendons, and muscles. It can be caused by an injury, infection or other condition. Pain may be accompanied by swelling, tenderness or loss of movement.


The ends of the bones in a joint are covered with articular cartilage. In the normal process of aging, this cartilage in the knee begins to soften and break down. As the cartilage deteriorates, the bones of the knee joint begin to rub together, causing damage and discomfort. Symptoms include pain, swelling, and stiffness in the knee joint. It is best managed by weight management, functional strengthening, and in some cases, surgery.

Knee fracture

A knee fracture is a break in the bones of the knee joint. This typically happens as a result of trauma, such as a fall, or forceful blow. The kneecap (patella), lower thigh bone (femur), or the upper shin bone (tibia) may be affected in a knee fracture. Symptoms include severe pain, tenderness, and swelling, accompanied by deformity of the knee joint and inability to walk or put weight on the injured leg. Treatment initially is ice and immobilization. Once we determine the extent of the fracture, treatment may be surgical or nonsurgical.

Iliotibial (IT) band syndrome

The iliotibial band is a group of fibrous tissues that runs down the outside of the thigh, providing stability to the knee and hip. It is a long stretch of tissue that crosses 2 joints, so irritation at either the hip or the knee can easily be transmitted. IT band syndrome causes the fibers to tighten, causing the band to rub against the bone when the knee is bent. Symptoms include pain on the outside of the knee or hip that improves with stretching or rest.

Ligament injuries & tears

The knee joint has four ligaments (anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL)). These ligaments are tough, flexible fibers that link the bones together providing stability and controlling movement. Injuries to these ligaments may occur during sporting activities or with trauma, such as an abrupt twist or direct blow to the knee.

Symptoms include pain, swelling, and a pop at the moment of injury. It may be difficult to put weight on the affected leg, and the knee joint may feel loose and unstable. Many of these can be diagnosed by history and physical exam, but xrays and an MRI are also warranted to evaluate the extent of the injury

Meniscus tears

Menisci are c-shaped discs of cartilage located between the bones of the knee joint. In each knee there are 2 menisci, medial and lateral. Meniscus tears can happen suddenly as the knee ages or may be related to a twisting-type injury. Knees with arthritis will likely have degenerative, or age-related, meniscus tears. If there is a clear injury, the tear is often associated with swelling.

Treatment is based on symptoms and the nature of the tear. Most degenerative tears are managed with rest, activity modifications, injections, and time. Many traumatic tears in younger patients are considered for surgery.

Osgood-Schlatter disease

Osgood-Schlatter disease is a common cause of knee pain in growing adolescents. It is inflammation of the area just below the knee where the tendon from the kneecap (patellar tendon) attaches to the shinbone (tibia). It commonly begins during growth spurts. Because running and jumping activities place additional stress on the knee, young athletes are at increased risk; however, it can present even in sedentary adolescents.

In most cases, rest, anti-inflammatory medication, and stretching/strengthening exercises will relieve pain and allow a return to daily activities.

Osteochondritis dissecans

Osteochondritis dissecans occurs when the blood supply to part of the cartilage or bone in the knee (or other joints) is lost. That portion of cartilage or bone can develop small cracks or even break off entirely. In some cases, the fragment of bone or cartilage may lodge itself in between the bones of the joint, making movement difficult or impossible. Symptoms include pain, swelling, tenderness, and grinding or locking in the knee joint.

Infected knee replacement

If your knee replacement becomes infected, surgery may be necessary to correct the problem. Infections, though rare (<2%), are caused by bacteria traveling through the bloodstream. A systemic illness or traumatic dental work can sometimes be the culprit.

Symptoms of an infection include fever, chills, redness or swelling of the knee, and drainage from the surgery site. If you suspect that your knee may have an infection, you should consult your orthopedic surgeon for evaluation.

Failed knee replacement

Failure of a replacement knee joint can be caused by many factors, but the symptoms often include pain, swelling, instability, and stiffness. The knee components are a combination of metal and plastic, and in time, the parts can wear out. If you are concerned that you knee may no longer be working properly, you should see a joint replacement specialist for an evaluation. In some cases, knee revision surgery may be necessary to correct the problem.


Tendonitis is inflammation of the tendons, the tissue that connects muscle to bone. Tendonitis is caused by overuse (repetitive motion) or sudden injury. Tendonitis symptoms include pain in the tendon area, swelling, and loss of motion.

Patellar tendonitis is inflammation in the patellar tendon that often results from repetitive impact. It is also referred to as “jumper’s knee”. Rest, immobilization, anti-inflammatory medications, and physical therapy are the mainstays of treatment.

Quadriceps/Patellar tendon tears involve partial or complete disruption of the complex that powers knee extension. In most circumstances, if the muscles cannot power the knee to extend after an injury, surgery is recommended to restore the connection.