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December 2004

By Leah Jensen, MSPT; Stephanie Boggs, MPT; and Laura Ryan, OTR/L

Leah Jensen, MSPT, (right) demonstrates how to care for knee pain on Stephanie Boggs, MPT.

Patellofemoral pain, also referred to as anterior knee pain, is a common yet extremely difficult diagnosis to manage in the rehabilitation setting. Because the knee joint does not have the protection of fat tissue or muscles, it is exposed to environmental and anatomical stresses leading to a high incidence of injury.¹ The knee is vulnerable to injuries partly because it sits between two long lever arms, the tibia and the femur, with extremely powerful muscle groups controlling its motion. In addition to the tibia and femur, the patella rests on the anterior surface of the distal femur. This puts it at risk for direct trauma to the anterior and high stress forces to the posterior.

Patellofemoral pain can be extremely challenging to rehabilitate, primarily because the exact source of pain is often not clear. Patients often complain of diffuse discomfort in the region of the patella. A study performed by Scott Dye, MD, in which the lead author's knee was probed arthroscopically without intraarticular anesthesia, found that there is a wide range of sensation and localization to pressure among the many structures of the knee. For example, he found that the posterior surface of the patella had poor sensation and localization, whereas the fat pad, joint capsule, and anterior synovium had strong pain sensation and good localization.² This may help to explain why patients with a diagnosis of anterior knee pain have a hard time telling the provider where they hurt.

The knee comprises the tibiofemoral and patellofemoral joints, medial and lateral menisci, medial and lateral collateral ligaments (MCL and LCL), anterior and posterior cruciate ligaments (ACL and PCL), and the joint capsule. The tibiofemoral joint is the articulation of the tibia with the femoral condyles and is the largest joint in the body. The patellofemoral joint is the articulation of the patella with the femoral condyles, which occurs during movement between flexion and extension. The patella glides in the trochlear groove of the femur cranially, or toward the hip, when the knee is extended and caudally, or toward the foot, when the knee is flexed.

The medial and lateral menisci are the cartilage located between the tibia and femur and have a variety of functions. Key functions include absorbing shock, reducing friction by providing lubrication and nutrition to the joint, and increasing the congruency between the tibia and femur. The cruciate ligaments lie within the knee joint and are considered the primary rotary stabilizers of the knee. The ACL prevents anterior translation of the tibia on the femur, and the PCL prevents posterior translation of the tibia on the femur. The collateral ligaments are located on the sides of the knee and aid in medial and lateral support. The ligaments and surrounding muscles, including the quadriceps, hamstrings, and gastrocnemius, work together to contribute to the stability and strength of the knee joint.³

THOROUGH EXAMINATION
During the physical examination of the knee, many areas must be addressed. Components of a comprehensive examination will include subjective history, postural assessment, tests of function, palpation of bony and soft tissues, active and passive range of motion (ROM) measures, manual muscle strength tests (MMT), muscle length or flexibility tests, joint play assessment, and special tests.

A well-taken subjective history should provide enough information for the clinician to formulate a good understanding of the situation and diagnosis of the knee via nature of pathology, mechanism of injury, and functional limitations. Based on the subjective history, an initial hypothesis can be formulated to focus the objective portion of the examination. There is no specific order in which objective testing must be performed as long as all appropriate tests are completed.

Initially, the therapist will observe how the patient walks in from the waiting room, removes his or her socks and shoes, and moves between a sitting and standing position to determine their willingness to move. Note should be made of the patient's weight distribution to determine their tolerance to weightbearing on the affected side. Assessing gait and the ability to perform a single- or double-leg squat, lunge, jump, hop, and dynamic balance activities can test the patient's function. The therapist can then observe the anatomical position of the knee in standing, looking for swelling, biomechanical changes such as genu valgum, genu varum, or recurvatum, and asymmetries at the knee, as well as looking at the position of the hip and ankle. In addition, the therapist should inspect the patient's shoes.

Palpation of the knee can help identify location of an injury and its affected structures. While the patient actively flexes and extends the knee, the therapist should feel for the amount of movement that occurs at the patella as well as any sign of crepitus. The patella should follow a consistent path, or track, as the knee moves between flexion and extension. It is important to note whether it follows this path equally bilaterally or if the patella is tracking too far medially or laterally on the involved side.

The patient's active and passive ROM of knee flexion and extension, lateral and medial rotation should then be measured, looking not only for quantity, but also for elicitation of pain, stuttering, clicking, or locking. It is optimal to measure extension while sitting and flexion while prone. Normal ROM for knee flexion is 135°, extension is 0° or even slight hyperextension, and tibial external and internal rotation is 10°.

Imbalances of muscle strength of the knee, hip, and ankle may contribute to pain in the knee. With MMT, strength of the quadriceps and hamstring muscles should be assessed. Muscles distal and proximal to the knee should also be tested. In the hip, the abductors and extensors are key muscles that contribute to normal gait. The ankle musculature is just as important. If there is inadequate strength in the ankle, the stable base for the kinetic chain is missing. For example, without efficient ankle or hip strength, the foot may overpronate and the hip may adduct, creating a lateral translation of the patella and causing a painful knee.

The therapist should measure the girth of the knee to determine if edema or muscle atrophy is present. Consistency is important regarding where to mark the measurements. Swelling of the knee may inhibit range of motion and muscle activity, especially of the medial quadriceps.

Assessment of muscle length of the hamstrings, iliopsoas and rectus femoris, iliotibial band (ITB), quadriceps, and gastrocnemius/soleus musculature must be performed bilaterally. Limitations in muscle length may cause biomechanical changes throughout the lower extremity. For example, a tight hamstring may cause a pelvic asymmetry; a tight psoas may cause increased lumbar lordosis; a tight ITB and quadriceps may affect the tracking of the patella; a tight gastrocnemius may lead to compensatory movements in the ankle and overpronation of the foot during gait.

The quadriceps angle (Q-angle) is the angle between the quadriceps and the patellar tendon as measured by drawing a line from the ASIS (anterior superior iliac spine) to the mid patella to the tibial tubercle. Normally, the Q-angle in men is 13° and in women is 18°. An angle less than 13° may be associated with chondromalacia or patella alta. An angle greater than 18° may be associated with chondromalacia, subluxed patella, increased femoral anteversion, genu valgum, lateral displacement of the tibial tubercle, or increased lateral tibial torsion.³ With an increased Q-angle, the patella typically will rest laterally and cause increased forces on the lateral facet of the posterior patella.

There are several special tests for the knee. Special tests should be performed throughout the knee, not solely of the patella. The most common test for meniscus involvement is the McMurray's test. The valgus and varus stress tests are used to detect laxity in the MCL or LCL. The Lachman test is for ACL insufficiency and is more commonly used than the anterior drawer.⁴ The posterior drawer tests the integrity of the PCL. For patellofemoral testing, the Clarke's sign and McConnell tests are used. A common patellar instability test is lateral apprehension.

Other possible sources of pain - referred pain - should be ruled out in the examination. Possible referral sources may include the hip or the lumbar spine. Reflexes, dermatomes and myotomes in the lower extremity, as well as lumbar and hip screens can be used to rule these out as possible referral sites.

INDIVIDUALIZED REHAB PLANNING
There are many factors that should be considered in developing a comprehensive rehabilitation program for patients with anterior knee pain. These factors may include radiographic evidence of patellar position and patellar degeneration, joint mobility, soft tissue mobility and flexibility, muscle strength and endurance, and patient function. An individualized treatment plan will be effective following a thorough examination.

If a patient has had x-rays prior to physical therapy, obtaining a report from the physician can be useful. A sunrise view, in which the image is taken in line with the patella with the knee flexed to approximately 20° to 30°, may give constructive information about the resting position of the patella in the trochlear groove. Proper alignment of the patella decreases pressure by spreading the contact forces over a wider area. If the patella is resting medially or, more often, laterally, the initial treatment may include patellar taping for improved alignment. It is well documented that patients demonstrate decreased pain with exercise and ambulation with patellar taping techniques, although research is divided over the true repositioning or length of time the patella remains repositioned via taping.⁵

If upon examination, it is found that there is a lack of patellar mobility, performing soft tissue and patellar mobilization techniques may allow for more normalized movement of the patella throughout the range of motion. Patellar mobilization should be performed in the directions of stiffness and correlated with any losses of knee range of motion. These techniques can also be taught to the patient for self-mobilization as part of a home program.

Flexibility of the hamstring, quadriceps, gastrocnemius, long hip adductors, and ITB/tensor fascia lata muscle groups can help to reduce compressive forces of the patella on the femur, improve available range of motion of the knee, and prevent abnormal tracking of the patella in the trochlear groove. Passive and active stretching can be beneficial to improving flexibility, but must be performed consistently for long-term changes in muscle length to be achieved and maintained.

There should be a good balance of muscle strength between the hamstrings and quadriceps, as well as between medial and lateral muscles within these groups. Often with knee pain, the vastus medialis obliquus (VMO) is inhibited and can result in a laterally tracking patella due to the stronger vastus lateralis. Selective retraining of the VMO in conjunction with patellar taping, electrical stimulation, or biofeedback can be used to restore this balance, although there is much division in the literature about the specific methods used to isolate the VMO.^6-8

If there is a lack of strength at the ankle, the foot will tend to overpronate, resulting in medial tibial rotation and maybe making the patella track laterally. By controlling the foot position and its timing of motion, tibial rotation may be reduced and the patella may track in a more neutral position. If strengthening does not correct the foot and ankle, orthoses may be required. Similarly, proximal support that comes primarily from the hip abductors and gluteal muscles is essential for proper biomechanics of the lower limb.

CKC VERSUS OKC
In general, closed kinetic chain (CKC) exercises are preferred for patients with patellofemoral pain. The thought is that there is less contact force through the patellofemoral joint in CKC exercises than in open kinetic chain (OKC) exercises. A CKC program is also considered more functional. Although this can be true, OKC exercises do not need to be entirely avoided as long as they are applied judiciously. The therapist needs to be aware that there can be excessive patellofemoral joint stresses with either CKC or OKC exercises. Research has shown that while OKC exercises produce high levels of force toward full knee extension, CKC exercises produce high patellofemoral forces toward full flexion.^9,10 For example, an open chain knee extension may be well tolerated if the range is limited to 90°to 40°, while a closed chain leg press may be detrimental if performed at greater than 90°.

FUNCTIONAL GOALS
Another key component in developing a rehabilitation program for patellofemoral pain is the patient's function at admission and their goals for discharge. The type and level of exercise for a competitive 18-year-old gymnast will be far different than those for an 80-year-old man who wants to be able to climb his stairs. Patient education is often required if the patient has unrealistic goals for their potential future activity level.

Although challenging, patients with patellofemoral pain can have positive outcomes. With a thorough subjective history and physical examination, the clinician can devise an individualized and comprehensive treatment plan. This plan can then be modified based on patient tolerance and progress to maximize their overall pain reeducation and functional recovery.

Leah Jensen, MSPT, is a physical therapy expert technician; Stephanie Boggs, MPT, is a staff physical therapist; and Laura Ryan, OTR/L, is a staff occupational therapist with Spaulding Rehabilitation Hospital Network, Framingham, Mass.

REFERENCES

Hoppenfeld S. Physical Examination of the Spine and Extremities. Norwalk, Conn: Appleton-Century-Crofts; 1976:171-96.
Dye SF, Vaupel GL, Dye CC. Conscious neurosensory mapping of the internal structures of the human knee without intraarticular anesthesia. Am J Sports Med. 1998;26:773-77.
Magee DJ. Orthopedic Physical Assessment. 3rd ed. Philadelphia: WB Saunders Co; 1997:506-98.
Katz JW, Fingeroth RJ. The diagnostic accuracy of ruptures of the anterior cruciate ligament comparing the Lachman test, the anterior drawer sign, and the shift test in acute and chronic knee injuries. Am J Sports Med. 1986;14:88-91.
Larsen B, Andreasen E, Urfer A, Mickelson MR, Newhouse KE. Patellar taping: a radiographic examination of the medial glide technique. Am J Sports Med. 1995;23:465-471.
Gilleard W, McConnell J, Parsons D. The effect of patellar taping on the onset of vastus medialis obliquus and vastus lateralis muscle activity in persons with patellofemoral pain. Phys Ther. 1998;78:25-32.
Salsich GB, Brechter JH, Farewell D, Powers CM. The effects of patellar taping on knee kinetics, kinematics, and vastus lateralis muscle activity during stair ambulation in individuals with patellofemoral pain. J Orthop Sports Phys Ther. 2002;32:3-10.
Callaghan MJ, Oldham JA. Electric muscle stimulation of the quadriceps in the treatment of patellofemoral pain. Arch Phys Med Rehabil. 2004;85:956-62.
Escamilla RF, Flesig GS, Zheng N, Barrentine SW, Wilk KE, Andrews JR. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Med Sci Sports Exerc. 1998;30:556-69.
Steinkamp LA, Dillingham MF, Markel MD, Hill JA, Kaufman KR. Biomechanical considerations in patellofemoral joint rehabilitation. Am J Sports Med. 1993;21:438-44.

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