Today we have a guest blog from physio and researcher Anthony Teoli covering a common problem we see a lot in clinic; osteoarthritis of the knee. Anthony graduated from McGill University with a Master’s of Science in Physical Therapy and currently works as a physiotherapist in a private physiotherapy clinic in Montreal. He is also the founder and editor of InfoPhysiotherapy, an educational website dedicated to promoting evidence-based practice among physiotherapists and educating the general population concerning injury prevention and management, as well as healthy living. Anthony has a keen interest for research and knowledge translation, having conducted two research studies examining the relationship between knee osteoarthritis and walking biomechanics. This research was presented at provincial, national and international conferences. His first peer-reviewed article was published in July 2016, along with two co-authors.

Like & Follow InfoPhysiotherapy on Social Media: 

Facebook: and Twitter: @InfoPhysioPT

Gait analysis in patients with knee osteoarthritis (OA) has been extensively studied in order to gain a deeper appreciation of changes in dynamic loading with disease progression. This is functionally relevant, seeing as dynamic loading occurs most frequently while walking when compared to other activities of daily living. In addition, walking is an activity that is commonly reported as difficult by patients with knee OA, likely secondary to pain or stiffness at the knee joint.

Research has demonstrated neuromuscular alterations in patients with knee OA when compared to asymptomatic individuals, as well as between knee OA severity groups. In particular, co-activation of the knee joint musculature in individuals with knee OA has been consistently reported, and will be the primary focus of this article.

One study published in 2004 by Childs et al., demonstrated that the vastus lateralis, medial hamstrings, tibialis anterior and medial gastrocnemius remained contracted 1.5 times longer than the same muscles in the control subjects. Significant increases in muscle co-activation were also observed in individuals with knee OA during walking.

In a more recent study by Astephen et al., published in 2008, participants with moderate knee OA demonstrated higher co-activation of lateral knee joint musculature (lateral hamstring and lateral gastrocnemius) compared to the control group. However, only the prolonged lateral gastrocnemius contraction was found in those with moderate knee OA and more elevated pain levels.
Similar results were found in a study by Hubley-Kozley et al., published in 2009, examining the co-activation differences in lower limb muscles between asymptomatic controls and those with varying degrees of knee OA during walking. Participants with severe knee OA demonstrated higher amplitudes for the two vasti muscles (medialis and lateralis) and the two hamstrings (grouped into medial and lateral hamstrings) for most of stance phase compared to both the moderate OA and the asymptomatic groups. In addition, the moderate OA group had elevated activity for the vastus lateralis and lateral hamstring only compared to the asymptomatic group. Their study also noted a trend for steadily decreasing gait speed from asymptomatic individuals to those with severe knee OA.

Putting It all Together

For the sake of time and simplicity, I have presented only several of the available studies that have demonstrated neuromuscular alterations. There is ample evidence to suggest that neuromuscular patterns differ between asymptomatic controls and those with knee OA. These results also shed light on the potentially different neuromuscular recruitment strategies adopted by those with varying degrees of knee OA severity. For instance, the increase in lateral knee joint muscular co-activity found in individuals with moderate knee OA may be effectively to offload the medial compartment of the knee, which is the site most commonly affected by knee OA. Thus, reducing the loading in the medial tibiofemoral compartment would in theory, slow the progression of the disease. The latter theory coincides with actual postural adaptations that are commonly adopted by individuals with knee OA such as slight lateral trunks lean over their affected leg and toe-out gait patterns, which effectively bring the ground reaction force closer to the knee joint center, reducing the lever arm, and in turn, reducing the knee adduction moment and the loading in the medial compartment of the knee.

According to the presented research, there seems to be a trend toward an overall increase in knee joint musculature co-activity in those with later stage knee OA, with a relative increase in medial knee joint musculature co-activity in severe knee OA participants when compared to those with moderate knee OA. These findings could be a protective response to the significant medial joint space narrowing and instability typically found in those with severe knee OA. Therefore, the increased medial knee joint musculature co-activity seen in patients with severe knee OA would theoretically increase medial knee joint stability. These findings are consistent with those of a study published in 2008 by Schmitt et al., who demonstrated increased co-contraction of knee muscles in patients with medial knee osteoarthritis and subjective reports of knee instability.

Why Is This Relevant?

The external knee adduction moment is a common gait variable that is measured via inverse dynamics. It is the estimate of the dynamic loading in the medial compartment of the knee joint, which is more commonly affected in patients with knee OA (Ledingham et al., 1993). The knee adduction moment has been shown to predict knee OA progression (Miyazaki et al., 2002), which supports excessive knee joint loading as a potential risk factor for the progression of knee OA (Sharma et al., 2006). Other contributors to knee joint loading that mustn’t be overlooked are abnormal muscle force and coordination. As a result, they too must be considered as a potential influence on disease progression (Winby et al., 2009). Moreover, recent data from a study by Hodges et al. published in 2016, demonstrated that increased medial knee muscle co-contraction was significantly related to a faster progression of medial knee OA, whereas increased duration of lateral muscle co-contraction actually had a protective effect against medial cartilage loss. This emphasizes the importance of exercise and biomechanical interventions to modify knee muscle activation patterns. The latter would essentially optimize knee joint biomechanics and reduce dynamic knee joint loading, which could potentially slow the progression of the disease.

Clinical Implications

Knee OA is a complex and multi-factorial disease that is influenced by many factors such as obesity, age, previous knee injury, gender (Silverwood et al., 2015), excessive knee joint loading (Sharma et al., 2006), knee extensor muscle strength (Oiestad et al., 2015) & genetics (Ryder et al., 2008), among others. In addition, alterations in gait kinematics are not limited to the knee. There is evidence for altered gait kinematics in individuals with knee OA at the level of the hip, knee and ankle when compared to asymptomatic individuals (Astephen et al., 2007).

I know it may all sound overwhelming and the overarching question truly is, “ok, but what do I do with my patients?” My advice would be to keep things simple. Firstly, focus on the modifiable risk factors, especially obesity. Motivate and encourage your patients to be active. The majority of my patients who are complaining of knee OA-related pain are fairly sedentary and have an elevated BMI, so a chunk of my effort is getting them moving to start off with. Another huge component of my treatment is patient education. A patient’s perception of their disease is crucial. You need to reassure them and gain their confidence first. Afterward, I’ll focus on neuromuscular training of the lower extremity (hip, knee and ankle) in order to improve sensorimotor control and obtain functional joint stabilization. These exercises should be functional by nature and relevant for the patient’s goals.

For those interested in more about education and neuromuscular training programs for knee osteoarthritis, I would highly recommend taking a look at the Good Life with osteoArthritis in Denmark (GLA:D) program, which is a fantastic example of implementation of evidence-based findings for knee and hip osteoarthritis.

For more on running and OA see Richard Leech’s excellent guest blog. We’ve also just released a series of free videos on achilles tendinopathy. Find out more HERE.


Childs, J.D., Sparto, P.J., Fitzgerald, G.K., Bizinni, M., Irrang, J.J., 2004. Alterations in lower limb extremity movement and muscle activation patterns in individuals with knee osteoarthritis. Clinical Biomechanics 19, 44-49. Link :

Astephen, J.A., Deluzio, K., Caldwell, G.E., Dunbar, M., Hubley-Kozey, C.L., 2008a. Gait and neuromuscular pattern changes are associated with differences in knee osteoarthritis severity levels. Journal of Biomechanics 41, 868-876. Link :

Hubley-Kozey CL, Hill NA, Rutherford DJ, Dunbar MJ, Stanish WD (2009) Co-activation differences in lower limb muscles between asymptomatic controls and those with varying degrees of knee osteoarthritis during walking. Clin Biomech 24: 407-414. Link:

Schmitt LC, Rudolph KS (2008). Muscle stabilization strategies in people with medial knee OA: the effect of instability. J Orthop Res 26: 1180-1185. Link:

Ledingham J, Regan M, Jones A, Doherty M (1993) Radiographic patterns and associations of OA of the knee in patients referred to hospital. Ann Rheum Dis 52: 520-526. Link:

T. Miyazaki, M. Wada, H. Kawahara, M. Sato, H. Baba, S. Shimada. Dynamic load at baseline can predict radiographic disease progression in medial compartment knee OA. Ann Rheum Dis, 61 (2002), pp. 617-622. Link:

L. Sharma, D. Kapoor, S. Issa. Epidemiology of OA: an update. Curr Opin Rheumatol, 18 (2006), pp. 147-156 Link:

Winby CR, Lloyd DG, Besier TF, Kirk TB (2009) Muscle and external load contribution to knee joint contact loads during normal gait. J Biomech 42: 2294-2300. Link:

Silverwood, V., Blagojevic-Bucknall, M., Jinks, C., Jordan, J. L., Protheroe, J., & Jordan, J. P. (2015). Current evidence on risk factors for knee OA in older adults: a systematic review and meta-analysis. OA and Cartilage, 23(4): 507-515. Link:

Øiestad, B. E., Juhl, C. B., Eitzen, I., & Thorlund, J. B. (February 01, 2015). Knee extensor muscle weakness is a risk factor for development of knee osteoarthritis. A systematic review and meta-analysis. Osteoarthritis and Cartilage, 23, 2, 171-177. Link :

Ryder JJ, Garrison K, Song F, Hooper L, Skinner J, Loke Y, Loughlin J, Higgins JP, MacGregor AJ. Genetic associations in peripheral joint OA and spinal degenerative disease: a systematic review. Ann Rheum Dis. 2008; 67:584–591. [PubMed: 17720722]. Link:

Astephen, J. L., Deluzio, K. J., Caldwell, G. E., & Dunbar, M. J. (March 01, 2008). Biomechanical changes at the hip, knee, and ankle joints during gait are associated with knee osteoarthritis severity. Journal of Orthopaedic Research, 26, 3, 332-341. Link :