Bridgette, a 26-year old white female presents with a six-month history of right knee pain. Although she cannot attribute the onset of her pain to a particular activity, she thinks it may have started after beginning to train for an upcoming marathon.

While the pain had previously been intermittent, Bridgette states it has become progressively more frequent and intense. The pain is somewhat diffuse but commonly occurs along the medial side of the knee, particularly along the medial edge
of the patella.

She experiences no pain when resting but says the pain can rate as high as an eight on a scale of zero to ten during physical activity. Her pain can get so intense at times that she must stop activity. Once she stops activity, the pain fades after a few days.

Bridgette has been running four to five miles per day for exercise for more than a year. Recently, she has been logging many more miles in preparation for the marathon. Bridgette notes that running does exacerbate her knee pain and she is concerned about how the pain will impact her training. Her training calls for increases in mileage for three months until the marathon. She is not interested in taking off for an extended period of time.

Bridgette’s knee pain also increases when she descends stairs, kneels or sits for longer than 90 minutes. She says ice and rest are helpful for short-term relief but do not help increase her level of function. She adds that leg extensions, suggested by a peer, aggravate the medial knee pain.

What The Physical Exam Reveals
Bridgette is a well-developed, well-nourished female in no apparent distress. Her body mass index (BMI) is 19.8 and her temperature, blood pressure and heart rate are normal.

Bridgette’s past medical history is non-contributory. She does not recall trauma to her knee and denies any locking, catching or slipping of the joint. The right knee is normal in color and does not feel warm to the touch. There is no tenderness over the patellar and quadriceps tendons, or the lateral joint line. However, there is tenderness over the medial patellar facet and slight tenderness along the medial joint line.

Her right knee’s passive range of motion is normal into flexion but the clinician appreciates a bit of patellar crepitus with knee bending. Bridgette can hyperextend her right knee by five degrees but this is symmetrical to the left. She is able to contract her quadriceps muscle well and symmetrically to the left side.

Manual muscle testing reveals 5/5 strength throughout the lower extremities with the exception of 4/5 strength for right hip abduction including both the tensor fascia lata and gluteus medius.

Bridgette also complains of pain along the medial border of the patella during knee extension testing. The pain is more pronounced when tested at five to 10 degrees of knee flexion as opposed to flexion at 80 to 90 degrees. Her hamstring and quadriceps flexibility are normal bilaterally. Lachman’s, varus and valgus stress testing in full extension and 20 degrees of flexion are negative. The McMurray test and posterior drawer testing are also negative. The neurological testing is normal. She does have a positive Clarke’s sign.

Bridgette’s standing alignment is normal at the knee. There is no genu varus or valgus, and her patellas point directly forward. She has normal arch heights in her feet, maintains these heights while standing and is able to fully squat without pain. Her gait is normal and non-antalgic with appropriate heel strike, pronation and supination throughout her stance with good push-off.

When the clinician asks Bridgette to unilaterally squat, she demonstrates good control of her left lower extremity but has a hard time maintaining good control of her right lower extremity. Specifically when she squats, her right femur internally rotates, placing her right knee medial to her foot at the lowest point of the squat.

When performing a lateral step-down maneuver from a six-inch step, Bridgette is able to control the descent well on her left side but demonstrates a similar deviation to the squat with her right lower extremity.

Bridgette takes 400 mg of ibuprofen one to two times per day for the pain but is uncertain of its effectiveness. Her only other medication is norgestimate/ethinyl estradiol (Ortho Tri-Cyclen, Ortho-McNeil). Standard A-P and lateral radiographs of her knees are unremarkable.

Which of the following is the likely diagnosis?
A. Medial meniscus tear
B. Iliotibial band friction syndrome
C. Patellofemoral syndrome

Key Insights Into The Differential Diagnosis
A. A medial meniscus tear is possible considering Bridgette’s recent increase in weightbearing activity and medial joint tenderness. Bear in mind that joint line tenderness reportedly has sensitivity and specificity ranging from 55 to 85 percent and 29.4 to 67 percent respectively.

Accordingly, joint line tenderness is of questionable value by itself when it comes to diagnosing a medial meniscus tear. The patient’s McMurray test is negative and this test reportedly has sensitivity and specificity values between 16 and 37 percent and 77 and 98 percent respectively.

While a McMurray’s test may not be helpful in identifying meniscal tears, it is a relatively good indicator in ruling them out.
Bridgette’s ambiguity regarding the exact mechanism of injury makes a medial meniscus tear less likely. Most patients in their twenties report pivoting/twisting type mechanisms that cause meniscal tears as opposed to degenerative-type lesions that often occur among older individuals.

Other factors that make the meniscal tear less likely include Bridgette’s ability to squat. This activity increases the compression forces on the menisci, particularly the posterior horn of the meniscus where most tears occur. The ability of the clinician to reproduce pain with resisted knee extension makes the diagnosis of a medial meniscus tear less likely.

B. Iliotibial band friction syndrome (ITBFS) is not the correct answer. Although ITBFS is a common injury among runners, Bridgette does not present with many of the examination findings that characterize ITBFS.

Repetitive rubbing of the iliotibial band (ITB) across the lateral femoral epicondyle of the leg causes ITBFS. This usually occurs at approximately 30° of knee flexion just after heel strike when the patient is running. This repetitive rubbing often causes thickening of the ITB as it passes over the lateral femoral epicondyle.

Often, clinicians can reproduce pain in this area with direct palpation and repeated extension of the knee around 30 degrees of knee flexion. However, Bridgette’s history and physical examination do not support this.

C. Patellofemoral syndrome is the most likely diagnosis. Clinicians also refer to patellofemoral syndrome as anterior knee pain and chondromalacia patellae. It is more common in females and is a prominent knee complaint in runners and young adults.

The prevailing thinking is that the most common cause of patellofemoral syndrome is abnormal tracking of the patella as it moves along the femoral groove during knee flexion and extension.

Abnormal tracking of the patella places excessive compression force on the articular cartilage of the patella’s undersurface. Without appropriate treatment, patellofemoral syndrome can eventually cause cartilage erosion.

Bridgette’s history includes many hallmark features that characterize this condition. These features include:
• an insidious onset that gets worse with increased activity;
• complaints of pain along the medial border of the patella; and
• increased pain with ambulation down stairs and after sitting for extended periods of time.

Descending stairs and sitting for extended periods of time increase pain and compression forces on the patellofemoral joint. Other findings from the examination that support this diagnosis include:
• tenderness to palpation on the medial patellar facet;
• patellar crepitus with flexion/extension of the knee;
• a positive Clarke’s sign;
• pain in the terminal degrees of resisted knee extension; and
• a lack of femoral control during unilateral stance activities.

Pertinent Treatment Pointers
Clinicians should refer patients with patellofemoral syndrome to a physical therapist for a complete evaluation. Patellofemoral pain can be due to many factors. A thorough musculoskeletal examination is a must.

Quadriceps weakness, foot overpronation, lower leg muscle inflexibility and proximal weakness, particularly in the hip abductors, may contribute to patellofemoral syndrome.

Although researchers have shown that quadriceps strengthening is an effective intervention, biomechanically correct quadriceps exercise is necessary to ensure the condition does not become worse. Specifically, quadriceps strengthening that decreases patellofemoral compression forces on the joint is necessary.

Dr. Gard is a Clinical Associate Professor and Associate Director for Programs in the Physical Therapy and Rehabilitation Sciences Department of Drexel University in Philadelphia.

Dr. Auth is a physician assistant and is the Director of the Drexel Hahnemann Physician Assistant Program at Drexel University
in Philadelphia.