Runner’s knee or patellofemoral pain syndrome (PFPS) is a condition used to describe the knee pain found in runners. The pain is mostly as a result of chronic overuse of the knee joint. The condition mostly affects young adults with a history of increased training.
Although the exact cause is unknown, problems between the kneecap and the lower end of the thigh bone have been suggested. Other conditions such as chondromalacia patella, iliotibial band syndrome, and plica syndrome may also sometimes be referred by runners knee.
The condition is usually self-limiting and mostly present in recent runners or undertrained runners who have increased their running distance. There may be multiple causes of patellofemoral pain syndrome. Chondromalacia patella is due to the softening of the cartilage at the undersurface of the kneecap.
Iliotibial band syndrome is due to friction of the iliotibial band. The band passes over with the outer surface of the lower end of the thigh bone (femur). Any tightness of the iliotibial band may cause friction with the outer surface of the femur.
Normal X-ray of the knee joint showing the various structures in the Anteroposterior and Lateral view.
X-ray showing Skyline’s view of the patella.
Mostly the only symptom is described as anterior knee pain which has a gradual onset. Patients often describe a vague pain located in front of the knee. Often patients touch the sides of the kneecap encircling it when asked to point the location of the pain. Some patients just describe it to be chronic pain present diffusely in the knee.
The pain is aggravated on activities involving bending, squatting, kneeling, getting up from a chair, or navigating stairs. A few patients may complain of associated swelling of the knee and cracking/popping sound in the knees. Patients complain of difficulty to bend and straighten the knee. They find it difficult to walk or run secondary to pain and swelling.
Causes & Risk Factors
Some patients may have a history of preceding trauma or blow to the knee. The chronic overuse of the tendons and muscles is a major cause of pain in the runner’s knee. In the case of runners, a history of change of activity is usually present. Inadequate training before running is usually one of the most common causes of the condition.
Runners may report a sudden increase in running distance. New runners may complain of pain with a history of running on concrete surfaces without adequate training. Training athletes may be affected due to strenuous overuse of the muscles around the knee.
Malalignment of the knees due to deformities such as knock knees or bow legs is a cause of the runner’s knee. Excessive unequal pressure on the kneecap results in patellofemoral pain syndrome. Patellofemoral mal-tracking is another cause of pain in front of the knee.
Flat feet deformity or other deformities of the foot and ankle may contribute to the symptoms of runner’s knee. Flat feet are caused by weak arches on the inner side of the foot. The unequal weight distribution leads to increased stress on the undersurface of the kneecap.
The weakness of the muscles of the thigh (Quadriceps) may result in increased strain over the kneecap causing pain. The increased strain from different causes results in bone bruises or swelling of the bone. The resulting synovial fluid irritation together with subchondral bone swelling causes pain and inflammation.
The physician will take a detailed history of the events surrounding the knee pain. A thorough physical examination of the knee joint is done. The angles formed by the kneecap with the thigh bone are measured.
Special physical tests are done to check for stability of the knee ligaments and meniscus. Sprains or tears of the anterior cruciate ligament, posterior cruciate ligament, medial and lateral collateral ligaments may also cause knee pain. Kneecap tracking and stability are also evaluated with physical tests.
Often, imaging tests are requested for further evaluation. Usually, an x-ray is done followed by an MRI. MRI gives information about the soft tissue structures inside the knee joint. Imaging tests are also useful to differentiate runners knee from other medical causes of knee pain.
The management of the runner’s knee is mostly conservative. Conservative management involves adequate rest to the knee. Patients are advised to avoid activities that strain the knee joint. Activities such as squatting, kneeling, running, or sitting and standing for extended periods of time are to be avoided.
Compression bandages are advised to help reduce swelling and provide support. Analytics in the form of NSAIDs such as ibuprofen or naproxen may be prescribed to help reduce pain and inflammation. Frequent icing with ice packs is advised to the patient. Leg elevation while sitting or laying down is advised to control swelling.
Orthopedic shoes with arch supports are recommended for flat feet. Knee braces may be helpful to provide support. Quadriceps strengthening exercises at home or with the help of a physical therapist are beneficial to prevent runner’s knee. Strengthening exercises may be isotonic or isometric.
Surgical treatment is reserved for patients who don’t benefit from conservative management. Surgical management is usually done using an arthroscope. The procedure involves the insertion of a minute camera along with miniature instruments through keyholes.
The camera is linked to an outside display for a live feed that the surgeon uses to guide the instruments. Surgical debridement using an arthroscope involves the shaving of a small fragment of the kneecap cartilage. Removal of the small part of the cartilage provides significant relief in most patients.
The surgery can also be used to release tight structures on the outer part of the knee joint. The tight tendons may pull the kneecap out of its groove during the range of motion causing pain. In patients with the mal-aligned kneecap, a kneecap repositioning surgery may be performed.
The repositioning surgery involves the removal of a small bone in front of the upper part of the leg bone. The bone along with the tendon is repositioned to allow better alignment between the kneecap and thigh bone.
Most patients report significant relief with conservative management. In a long time, the best medical advice in the treatment for runner’s knee remains physical therapy. Runners knee problem not amicable to conservative management may require surgical treatment from a sports medicine specialist.