Sunday, August 27, 2023

What Causes Running Injuries?

Navicular drop from Physiopedia
Recently we have seen more runners coming to see us in our clinics. A few are preparing for the Berlin marathon next month while others are preparing for ultras and the local Stan Chart marathon later in the year. What was common is their lack of gluteus medius strength, sudden increase in training loadchange in running shoes amd not enough recovery.

How did my observation compare to a published research on factors associated with running related injuries? This group of researchers aimed to identify factors associated with running related injuries and also to evaluate their potential in injury screening.

274 recreational runners were recruited for their study. At baseline, running technique, clinical measures (strength, range of motion (ROM), foot position), impact loading, injury and training history were collected. These runners were followed up fortnightly for 1 year.

49 runners dropped out leaving 225 (84 females, 141 males) for the final analysis. 52 percent experienced a running related injury. Calf strain (15 percent), Achilles tendon injury (11 percent) and plantar fasciitis (9 percent) made up the largest proportion of injuries.

After adjusting for age, weekly mileage and sex, the following factors were statistically significant and associated with increased likelihood of injury. Previous injuries in the past year, less navicular drop, weaker hamstrings and measures of running technique (knee, hip and pelvis kinematics) were associated with increased likelihood of injury.

There were significant associations between running injuries and hip and knee kinematics like contralateral (opposite side) pelvic drop and increased knee inward rotation. All of which I have written about before in a previous post.

I was surprised that the calf constituted the highest proportion of injuries. I (falsely) assumed the knee would be the most common site of injury. Perhaps popularity in adopting forefoot and midfoot running styles (which takes load away from the knees but transfer them to the calf, ankle and Achilles) compared to heel striking which loads the knee more. 

Another study found shin splints and stress fractures followed by Achilles tendon injuries to be the most common diagnosis in recreational runners (Mulvad et al 2018).

Only the navicular drop test (not strength, ROM, foot positioning among the clinical measurements) was associated with injury. The navicular drop is a measurement of how much the navicular bone moves from a neutral sitting position to standing. The larger the movement, the larger the collapse of the arch of the foot. 

The researches found that the less navicular drop, the higher the chances of injury, a navicular drop <10mm increased injury odds by 2 times. Values of the navicular drop test in this study would place the uninjured runners in the "pronated" foot category and the injured runners in the "neutral" foot category.  

The researchers explained that uninjured runners may have a more flexible foot with increased capacity to absorb loads. This supports emerging evidence that flat feet may be protective in nature as compared to previous views that flat feet needs 'support'. 

One of my often copied Shoe Lists update

For years, podiatrists, coaches and shoe salesmen have looked at your foot type (to see if you have normal, low or high arches) (pictured above), then recommended that you have stability, motion control and cushioned shoes respectively. The rationale being that if you had high arches, you did not pronate enough and needed softer, well cushioned shoes while if you had low arches, you tend to overpronate and needed sturdy motion control shoes to control that overpronation. Runners with normal arches needed neutral shoes and were prescribed stability shoes. This method was deeply rooted in athletic circles and widely accepted. Time to bin that permanently.

 Also relate this to wearing orthotics. Patients are to told that orthotics help prevent the arch from "collapsing". This study shows that if the arch does not collapse (or drop) more than 10 mm,  you are twice as likely to get a running injury. Something to mull over for runners who have been told to wear orthotics. We (sports doctors, physiotherapists, podiatrists etc) MUST definitely reconsider running injury prevention and treatment techniques aimed at correcting 'overpronation' since there is no association between foot eversion (pronation) and running injuries in this study.

Previous injuries less than a year ago was a strong predictor of getting injured again. This may indicate that some runners have not regained original tissue strength or they have alterations in technique that increase their vulnerability to injury. 


Dillon S, Burke A, Whyte EF et al (2023). Running Towards Injury? A Prospective Investigation Of Factors Associated With Running Injuries. PLoS One. 18(8): e0288814. DOI: 10.1371/journal.pone.0288814

Mulvad B, Nielsen R, Ling M et al (2018). Diagnoses And Time To Recovery Among Recreational Runners In The RUN CLEVER Trial. PLoS One. 13(10). pmd:30312310. DOI: 10.1371/journal.pone.0204742

Sunday, August 20, 2023

Statins And Their Effects On Tendons

Patella tendon pain
An article in today's Sunday Times (pictured below) mentioned that 50,000 people (or 1 out of 140) are at a very high risk of a heart attack due to an inherited gene mutation unless they take statins.
Sunday Times 200823
Statins (pictured below) are medications that reduce the levels of bad cholesterol or low level lipoprotein (LDL) in your blood and protect the insides of your arteries. When cholesterol is reduced, it lowers the risk of developing heart and circulatory diseases including stroke and heart attacks.
A study of 594,130 participants found that statin medications regardless of statin types were associated with a  significantly greater risk of all types of tendinopathy development compared with no statin treatment. This is inclusive of tennis elbow, trigger finger, rotator cuff tendinopathy, Achilles tendinopathy and De Quervain's (or radial styloid) tenosynovitis. There were 84,102 statin users and 168,204 non users (control) in that study (Kwak et al, 2023).

Tendinopathy is the term used now when there is pain and dysfunction in our tendons instead of tendinitis. It is associated with overuse in and around tendons and characterised by pain, reduced function and reduced exercise tolerance. There is seldom inflammation found in the tendons, it is more of a failed healing response of the tendon leading to disruption of collagen fibers in the tendon.

The oxygen consumption of tendons and ligaments during exercise is 7.5 times lower than skeletal muscles (Radak et al, 2013). This low metabolic rate and well developed anaerobic energy generation capacity are needed to carry loads and maintain tension for long periods when we are standing, moving and exercising. 

When blood flow (carrying oxygen) is restricted or reduced in tendons, it can lead to necrosis (or death) of the cells in the tendons. A low metabolic rate also results in slow healing after injury.

What we know about tendinopathy is that it does not improve with rest. The pain may ease but returning to activity/ sports is often painful again since rest does not increase the tolerance of the tendon to load. There is usually very little inflammation invloved in tendinopathy, hence it is not considered a classic inflammatory response. Anti inflammatory medication may help if you have very high pain levels, but it is still unclear what effect they have on the cells.

Tendinopathy can be caused by many different factors, the main factor being a sudden change in certain activities like running and jumping where the tendon is required to store energy. Some people are predisposed beacause of biomechanics (poor endurance or poor muscle capacity) or systemic factors (age, menopuase, elevated cholesterol and other metabolic factors). Predisposed people may develop tendon pain even with little changes in their activities.

Modifying load is very important in settling tendon pain. Reducing tendon load (at least in the short term) always helps.

Pathology on scans does NOT equal to pain. MRI scans often show tendon 'damage' (or abnormality) in people without pain. Even if you have 'tears' or 'severe' pathology DOES NOT mean you will have a better or poorer outcome. The pathology may not improve even with the best intentioned treatment (not on scans anyway), so treatment should be targeted at improving pain and function.

Tendinopathy rarely improves with passive treatments like massages, therapeutic ultrasound, injections and extracoporeal shock wave therapy (ESWT). Note that not all ESWT machines are the same. Most if not all physiotherapy clinics use hand held ESWT devices that do not require licenses. The doctor operated devices (with ultrasound imaging requiring a license to operate) usually cost over $250,000 versus the less than $40,000 cheaper versions that do not require licenses.

Eccentric (or lengthening) exercises seems to be the most evidenced based treatment for tendinopathy. This allows the tendons to be loaded progressively so they can develop greater tolerance that one needs for day-to-day activities or sports. I'm not a fan at all about getting our patients to do exercises, but even I had to do some eccentric strengthening exercise. The hands on fascia treatment I received definitely helped, but the individualised ecccentric exercise was the final part of the puzzle.

Tendinopathy responds very slowly to exercise, so patience is definitely needed while doing the correct eccentric exercises and it also needs to be progressed appropriately. Resist the temptation to accept 'short cuts' like injections and surgery.


Andres BM and Murrell GA (2008). Treatment Of Tendinopathy: What Works, What Does Not, And What Is On The Horizon. Clin Orth Relat Res. 466(7): 1539-1554. DOI: 10.1007/s11999-008-0260-1

Kwak D, Moon SJ, ParkJW et al (2023). Effects Of Statin Treatment On The Development Of Tendinopathy: A Nationwide Population-Based Cohort Study. Orth J Sp Med. 1197): 23259671231167851. DOI: 10.1177/23259671231167851

Radak Z, Zhao Z, Koltai E et al (2013). Oxygen Consumption And Usage During Physical Exercise: The Balance Between Oxidative Stress And ROS- Dependent Adaptive Signaling. Antioxi Redox Signal. 18(10): 1208-1246. DOI: 10.1089/ars2011.4498

Sunday, August 13, 2023

Time To Shake Legs?

The terms "shake leg" and "jiak zhua" (eat snake in Hokkien) is a local colloquialism or slang used to describe a person's attitude towards work or tasks. It means slacking off from work and responsibilities.

When I write you have reasons to "shake leg" now, it does not mean I'm asking you to skive at work. Not at all.

I am suggesting that you can do a tiptoeing exercise while sitting down. Start with your foot flat on the floor, then raise your heel off the ground and let it fall back down. I am sure you have seen someone doing it in the office, restaurants or even at home.

Why shake legs? If done correctly, this movement activates your soleus muscle and boosts your metabolism during which blood sugar is utilized at high levels for hours (Hamilton et al, 2022).

When you work the soleus, it can also double the normal rate of fat burning between meals as found by Hamilton et al (2022). Test subjects were given a sugar drink before performing the soleus push-up (this is what Hamilton called the exercise in their study) in a controlled setting for 270 minutes (4.5 hours) spread through out the day. They found a 52 percent improvement in blood glucose fluctations and 60 percent less insulin requirement that lasted over 3 hours.

This is useful since elevated blood levels and fat levels are associated with metabolic syndrome - a collection of health issues that occur together including diabetes, high blood pressure, stroke and heart disease.

The soleus push-up may well help lower your blood sugar levels and reduce your risk of metabolic diseases since the soleus is made up up predominantly of Type 1 slow twitch muscle fibers. They are more fatigue resistant and can be exercised for longer which will lead to greater blood glucose being utilized. This is also why test subjects can do the soleus push up for 4.5 hours.

This would be especially useful for a desk bound person at work or home, especially if seated for long periods. They can be performed barefooted and do not require any extra space.

But 4.5 hours is a lot of time to be shaking your legs (soleus push-ups). The subjects did it in a highly controlled lab setting and I'm wondering it it can be replicated in a real life home or work setting. Even though it is a low intensity exercise, performing it for 4.5 hours may lead to delayed onset of muscle soreness( DOMs) initially for those not used to it and even other musculoskeletal problems like muscle cramps and strains.

Even though the soleus push-ups help with lowering your blood sugar levels, it cannot replaced other forms of exercise since it does not help with your aerobic fitness. They could be added to your other aerobic and strength training exercises instead of replacing them.

Shall we all shake our legs?


Hamilton MT, Hamilton DG and Zderic TW (2022). A Potent Physiological Method To Magnify And Sustain Soleus Oxidative Metabolism Improves Glucose And Lipid Regulation. IScience. 25(9): 104869. DOI: 10.1016/j.isci.2022.104869

Sunday, August 6, 2023

Is The Single Leg Squat Assessment Valid?

Picture from Wilczynski et al, 2020
A visual assessment we use when seeing a patient in our clinic especially when they have knee or hip pain is the single leg squat (SLS). We stand the patient in front of a full length mirror and ask them do do a SLS on the non painful knee/ hip first before comparing with the painful side.

Picture from Vasiljevic et al, 2020
We look at the patient's movement quality when they execute the SLS. We observe how effective they are throughout the entire movement, their balance and fluidity to keep the knee stable instead of letting the knee flop inwards (or inward knee displacement). 

Being able to assess movement quality during the SLS can provide valuable insight into the risk of lower limb injuries. They are usually associated with the severity of symptoms and also helps with prognosis of lower limb injuries.

Assessing the patient visually like this is widely used in many health care, rehabilitation and injury prevention programs. This is also a much more cost effective alternative compared to complex biomechanical analyses. It's also much faster.

Ressman and colleagues (2019) have found that the SLS is both reliable and feasible for use in individuals with lower limb conditions.  However, a recent systematic review (Gomes et al, 2023) 'questioned' the validity (or soundness) of the SLS and whether it was useful in clinical settings (like health care clinics).

Gomes et al (2023) found 10 studies evaluating 3 different methods of visual assessment of the SLS (Crossley scale, Whatman score and medial knee displacement). They found very low to moderate certainty evidence that the 3 methods were totally accurate and sound. Hence, it may not be effective relying solely on visual assessment methods for clinical outcomes. 

They wrote that their findings DO NOT nullify the significance of assessing movement quality of patients but that it was essential for future robust research to develop scales that are sound. Only then that they can assist practitioners in their clinical decision making.

We will still use the SLS when assessing patients in our clinic. I defintely understand where the researchers are coming from. The need to justify whether our assessments and treatment work, otherwise governments, insurance companies and of course self paying patients will not want to come to us anymore.

A more experienced clinician would be able to discern movement quality over a less experienced one. Some of the included studies did not control for speed and depth of the squat. These confounding factors will affect movement quality. Some of the review's key findings were based only on one study, so findings should be interpreted with caution.


Gomes DA, Da Costa GV, Martins EC et al (2023). Are Visual Assessments Of The Single-leg Squat Valid To Be used In Clinical Practice? A Systematic Riview Of Measurement Properties Based On The COSMIN Guideline. PT in Sport. 63: 118-125. DOI: 10.1016/j.ptsp.2023.07.009.

Ressman J, Grooten WJA and Barr EA (2021). Visual Assessment Of Movement Quality In The Single Leg Squat Test: A Review And Meta-Analysis Of Inter-Rater and Intrarater Reliability. BMJ Open Sp Ex Med. 5:e00541. DOI: 1136/bmjsem-2019-00541.