June 2009

Early Signs of Runner's Knee Diagnosed with New Imaging Techniques

Anthony C. Luke M.D., M.P.H.
Director, UCSF Primary Care
UCSF Sports Medicine

Finishing a marathon was once considered one of the most challenging 10 sports activities. Each year, however, the number of participants in the "marathon club" increases. One common concern is that long distance running could cause irreversible cartilage damage, which can lead to osteoarthritis (OA).

In healthy cartilage, a continuous balance between the synthesis and catabolism of matrix components is required. On a biochemical level, marathon runners have increases in serum levels of tumor necrosis factor-alpha (TNF-alpha) and other markers for joint damage. Elevation of these markers within 24 hours after running suggests an inflammatory process, which is at least transient.

Loss of cartilage is preceded significantly by damage to the proteoglycan-collagen matrix. Loss of proteoglycan (PG) or glycosaminoglycan (GAG) is an initiating event in the early stages of OA, while the amount of collagen in the framework does not seem to be severely affected.

High field imaging techniques using a 3 Tesla MRI are emerging that can detect early biochemical degradation of articular cartilage before more obvious structural changes to the cartilage and OA occur. The high field 3 Tesla MRI has been shown to be superior in assessing cartilage morphology, as compared to standard MRI, which uses a 1.5 Tesla magnet. The technique is available at only a few select medical centers nationwide, including UCSF Medical Center.

Currently, we are studying the efficacy of the new MRI techniques for detecting damage to cartilage collagen-proteoglycan matrix in OA. Our research evaluates the cartilage of asymptomatic patients before and after running a marathon using T1rho weighted and T2 sequences, which can detect early cartilage proteoglycan breakdown and water content to assess cartilage biochemical composition.

Results from our research involving active runners demonstrated that nine out of 13 healthy running controls showed focal cartilage abnormalities, often found in the patellofemoral joint. T1rho and T2 values in active subjects with and without focal cartilage abnormalities differed significantly compared to individuals with OA (Stahl, Luke et al, Eur Radiol, 2009).

Our finding of early pathology in the cartilage of the patellofemoral joint helps explain why patellofemoral pain (PFP) or anterior knee pain, or "runner's knee," is the most common knee problem seen in primary care offices.

PFP is a multifactorial problem in which the main concern is excessive contact forces on the articular surfaces of the kneecap. Abnormal joint mechanics and overuse activities such as running, which can double the forces on the knee, are risk factors for developing PFP.

In addition, a recent study by Souza et al. found that altered hip function particularly in females with PFP provides clinical support that excessive femoral motions and rotations may contribute to faulty patellofemoral joint mechanics, particularly because the patella articulates with the femur. They suggest that assessment of hip kinematics and hip muscle performance become part of the examination in patients with PFP.

Gluteal hip function can be quickly screened for weakness by observing the patient performing a standing one-leg squat, and whether the knee internally rotates or the pelvis drops on the non-weight bearing side. Hip external rotation exercises, hip abduction exercises to strengthen the gluteus medius, and hip extension for the gluteus maximus can be recommended to help address any strength deficits.


RunSafe, a program of UCSF Sports Medicine, is designed for runners of all levels — from the novice to the seasoned competitor. Using the latest sports medicine research, our multi-disciplinary sports medicine specialists provide counseling and biomechanical assessment of running and training patterns to help runners prevent injuries and practice safe training methods.

Runners have a two-hour assessment, during which they receive a detailed running biomechanics analysis via video analysis as well as strength and flexibility, nutrition, foot and footwear assessments.

RunSafe accepts patients through referrals from primary care physicians and other specialists, as well as self-referrals.

For information about RunSafe, please contact (415) 353-7896.

For more information, contact the Physician Referral Service at UCSF Medical Center:

Phone(800) 444-2559
Email referral.center@ucsfmedctr.org

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