Clinical / Research

Swollen Knees

10-3A rough game soccer, perhaps a stopping after a sprint to the ball, maybe early osteoarthritis, whatever the case, a right knee effusion ensued a couple days after a friendly last week. An interesting experience. Sensations of a Ziploc bag full of water between by tibia and femur pervaded. As you would expect, the Brush/Wipe test was positive and there was very little pain unless I accidentally tried to extend my knee during terminal stance during walking. Things have pretty well settled but I cannot help but wonder how knee effusion may affect walking? Given the number of people with ACL or meniscal lesions or arthritis that need to walk while their knee is effused, this is a rather applicable question.

A recent grant application to the Nova Scotia Health Research Foundation was going to help sort this out.  Too bad they did not have enough money to fund it.  All was not lost however; we do have some information to help us out.

Rutherford, D. J., Hubley-Kozey, C. L., Stanish, W. D. (2012). Knee effusion affects knee mechanics and muscle activity during gait in individuals with knee osteoarthritis. Osteoarthritis and Cartilage, 20, 974-981. (Please see About Derek > Publications for full text)

Knee effusions have been reported in over half of the individuals treated for knee Osteoarthritis (OA) and there is evidence that knee joint effusions can provide a mechanism for knee OA progression (Krasnokutsky et al., 2011; Conaghan et al., 2010). In addition, if aspirated, effusion removal can improve functional recovery after knee ligament injury (Reeves and Maffulli, 2008) making it a significant factor to understand for advancing knowledge on knee mechanics and lower extremity function. It was difficult to find a study that investigated the role of knee effusion to alter how individuals walk, making this research pertinent to understanding gait mechanics and muscle activation patterns in individuals with knee osteoarthritis and effusion. While literature exists to study experimental effusion and quadriceps inhibition (Palmieri et al., 2004), only one study was found to address the effect of effusion on biomechanics and muscle activation during gait in healthy individuals (Torry et al., 2000). Folks adopted what is known as a “quadriceps avoidance gait”.  Their knees did not flex as much during early stance (which I did not experience), knees remained flexed during mid to late stance (which I did experience), they had reduced electrical activity in quadriceps and increased activity in hamstrings. This study looked at the immediate effects of effusion, but what if effusion lasts longer than 30 minutes, as mine has.  The mechanics of how fluid volume and capsule compliance can be rather complex (Simkin, 1995; Levick, 1983). It is however underdetermined whether these results could be applied to individuals with chronic knee effusions, perhaps in folks with knee OA.  Rather important given ¼ of our population might experience this disease in the coming decades.

In our study, effusion was identified using a manual, hands-on clinical test of dichotomy (Brush test – presence/absence) in a group of individuals with moderate knee OA. Good reliability has been shown for this detection method (Sturgill et al., 2009).  Knee joint motion and moments of force were monitored, along with muscle activation of knee joint musculature using state-of-the art gait analysis and EMG methodology. Pattern recognition techniques were employed for electromyogram analysis. Altered knee mechanics and muscle activation patterns were found when effusion was identified that have implications for long-term joint function and possibly linking effusion to knee OA progression through gait mechanics. The mid to late stance net external knee extension moment was less in individuals with effusion. The knee remained more flexed during stance and higher quadriceps and prolonged hamstrings activity during mid-stance were found with no effect on gastrocnemii when effusion was present.

The findings provide a foundation for understanding the role of knee effusion to alter knee joint function during gait in individuals with knee osteoarthritis.  While further study is warranted, these results suggest that effusion management should be a component in the multidimensional management of knee OA.

Clinical Considerations

  • In recent years, knee OA heterogeneity has been increasingly recognized in the literature and many studies elect to stratify across disease severity. For the moderate OA classification in this study, individuals were required to have radiographic evidence of knee OA scored using the Kellgren-Lawrence scale.  The scores were between I and III. All individuals were managed using conservative means and self-reported their ability to walk a city block, jog 5 meters and ascend/descend stairs reciprocally would not be limited by pain. If you know a patient with knee OA and similar characteristics, than this individual would be a close match to those currently studied.
  • Can physiotherapy treatments alter the state of knee effusion, either acute or chronic?  I’m interested in your thoughts. Lymphatic drainage is the natural mechanism of effusion removal and there does not appear to be evidence to support whether or not physiotherapists can influence this. In the UK, physiotherapists are able to aspirate/inject synovial joints (CSP).  Remember, absence of evidence does not mean evidence of absence. As such, we must try and understand more clearly our role in this management.  These results indicate that effusion status should be monitored in individuals with knee OA and if present, can alter the way individuals walk in the direction of increased joint loading and metabolic demand.


Conaghan, P.G., D’Agostino, M.A., Le, B.M., Baron, G., Schmidely, N., Wakefield, R., Ravaud, P., Grassi, W., Martin-Mola, E., So, A., Backhaus, M., Malaise, M., Emery, P., Dougados, M., 2010. Clinical and ultrasonographic predictors of joint replacement for knee osteoarthritis: results from a large, 3-year, prospective EULAR study. Ann.Rheum.Dis.. 69, 644-647.

Krasnokutsky, S., Belitskaya-Levy, I., Bencardino, J., Samuels, J., Attur, M., Regatte, R., Rosenthal, P., Greenberg, J., Schweitzer, M., Abramson, S.B., Rybak, L., 2011. Quantitative magnetic resonance imaging evidence of synovial proliferation is associated with radiographic severity of knee osteoarthritis. Arthritis. Rheum.. 63, 2983-2991.

Levick, J.R., 1983. Joint pressure-volume studies: Their importance, design and interpretation. J. Rheumatol. 10, 353-357.

Palmieri, R.M., Tom, J.A., Edwards, J.E., Weltman, A., Saliba, E.N., Mistry, D.J., Ingersoll, C.D., 2004. Arthrogenic muscle response induced by an experimental knee joint effusion is mediated by pre- and post-synaptic spinal mechanisms. J.Electromyogr.Kinesiol. 14, 631-640.

Reeves, N.D., Maffulli, N., 2008. A case highlighting the influence of knee joint effusion on muscle inhibition and size. Nat.Clin.Pract.Rheumatol. 4, 153-158.

Simkin, P.A., 1995. Feeling the pressure. Ann.Rheum.Dis.. 54, 611-612.

Sturgill, L.P., Snyder-Mackler, L., Manal, T.J., Axe, M.J., 2009. Interrater reliability of a clinical scale to assess knee joint effusion. J.Orthop.Sports. Phys.Ther. 39, 845-849.

Torry, M.R., Decker, M.J., Viola, R.W., O’Connor, D.D., Steadman, J.R., 2000. Intra-articular knee joint effusion induces quadriceps avoidance gait patterns. Clin. Biomech. 15, 147-159.


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