Your Knees Want to Take You Shoe Shopping

Newswise — The shoes you wear may have significant effects on your osteoarthritis of the knee, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Boston, Mass.

Knee osteoarthritis is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include being overweight, age, injury or stress to the joints, and family history can increase the risk of knee osteoarthritis.. Knee OA is increasing in frequency in our overweight and aging society.

In knee OA, there is abundant evidence that patients with abnormally high loading knees (high amounts of stress on part or all of the knee joint) are at increased risk of both injury and disease progression.

Researchers studied the effects of various types of footwear on 13 women and 3 men with knee OA. Each participant underwent gait analysis (evaluation of the way they walk and load their knees) while barefoot and while wearing a clog, a stability shoe (designed to limit foot movement), a flat, flexible walking shoe (designed to allow significant foot movement), and flip-flops.

After having time to adjust to their new footwear, each participant was observed walking at normal speed. Researchers calculated the load on the knee.

Researchers found that clogs and stability shoes were associated with significantly higher loading of the knees, while the walking shoes and flip-flops resulted in lower knee loads similar to those occurring when walking barefoot. Therefore, shoes that allowed natural foot motion and flexibility appeared to be more beneficial in terms of knee loading.

"These results highlight the importance of re-evaluating the design of modern day shoes in terms of their effects on knee loads and knee OA," said Najia Shakoor, MD, assistant professor of internal medicine, Section of Rheumatology, Rush Medical College; and an investigator in the study.

"Knee loads play an important role in the progression of knee osteoarthritis," she explains. "Shoes have traditionally been engineered to provide foot comfort and little previous attention has been directed to the effects that shoes may have on loading of osteoarthritic knees. Results from this study suggest that shoes can significantly affect the amount of load on osteoarthritic knees—with flat, flexible shoes providing the greatest degree of benefit in terms of knee loading."

The ACR is an organization of and for physicians, health professionals, and scientists that advances rheumatology through programs of education, research, advocacy and practice support that foster excellence in the care of people with or at risk for arthritis and rheumatic and musculoskeletal diseases. For more information on the ACR's annual meeting, see http://www.rheumatology.org/annual.

Editor's Notes: Mondira Sengupta, MD, will present this research during the ACR Annual Scientific Meeting at the Boston Convention and Exhibition Center from 9:00 " 11:00 am ET on Thursday, November 8, 2007, in the Exhibit Hall. Dr. Najia Shakoor will be available for media questions and briefing at 1:30 pm ET on Friday, November 9 in the on-site press conference room, Room 251.

Presentation Number: 186

The Effects of Common Footwear on Dynamic Joint Loading in Osteoarthritis (OA) of the Knee

Mondira Sengupta, Rachel A. Mikolaitis, Robert M. Trombley, Joel A. Block, Najia Shakoor. Rush University Medical Center, Chicago, IL

Purpose: OA of the lower extremity is largely mediated through aberrant biomechanical forces; in knee OA, there is abundant evidence that subjects with abnormally high loading of the knees (peak external knee adduction moment, AddM) are at increased risk of both incident and progressive disease. We recently demonstrated that in OA of the knee, walking barefoot significantly decreased the AddM compared to the subjects' own walking shoes (Arthritis Rheum 54:2923, '06). These data suggest that footwear may significantly affect joint loads at the knees. However, shoes have historically been engineered primarily for foot comfort, and the effects that various footwear have on joint loading are not clear. Herein, we evaluated the effects of several common shoe types on dynamic knee loading in people with OA of the knee.

Methods: 16 subjects (3 men, 13 women) with radiographic and symptomatic knee OA underwent gait analyses using an optoelectronic camera system and multi-component force plate. In each case, gait was evaluated barefoot and while wearing 4 different shoes: 1) Dansko clog 2) Brooks Addiction, a common "stability" shoe which limits foot mobility 3) Puma H-Street, a flat, flexible walking shoe allowing significant foot mobility and 4) flip-flops. Subjects were permitted to acclimate to each new condition prior to gait testing. The peak AddM (%body weight x height) was calculated at the knee during normal walking speed, and represented the primary endpoint. AddMs with each shoe type were compared to those during barefoot gait using a paired t-test, with p<0.05 considered significant.

Results: The mean age (±SD) of the subjects was 56±9 years. The peak AddMs at the knee during the different footwear conditions are listed in the Table. The Dansko clog and Brooks Addiction were associated with significantly increased AddM compared to barefoot walking, whereas there were no statistically significant differences in the AddM with the Puma and flip-flops compared to barefoot walking.

Barefoot Dansko Brooks Puma Flip FlopAddM (%BW*ht) 2.6± 0.7 3.0 ±0.7 3.0 ±0.7 2.8±0.7 2.6±0.7p-value <0.001 0.001 0.096 0.895

Conclusions: These data confirm that footwear may have significant effects on the peak AddM in subjects with OA of the knee. Specifically, flexible footwear is associated with loads similar to that of walking barefoot while more supportive, stability footwear results in significantly higher peak knee loads. In light of the strong relationship between excess knee loading and OA, the design and biomechanical effects of modern footwear may have a substantive role on the prevalence and progression of lower extremity OA.

Disclosure Block: M. Sengupta, None; R.A. Mikolaitis, None; R.M. Trombley, None; J.A. Block, None; N. Shakoor, None.