The Sunday morning long run has just finished, and the whole group heads to the banh cuon (steamed rice roll) stall at the end of the alley, perching on tiny, low red plastic stools. When you stand up to pay, your right knee twinges at the front. You can’t point to any one spot; you just feel pain around the kneecap, as if it were coming from behind it. It has been like this for weeks: by the eighth or ninth kilometer the knee aches, and a day of rest makes it better.
The stall owner sees you wince and, while handing back your change, tells you to buy a knee brace and rub on some warming oil tonight. The team captain has his own recipe: sit on the edge of the bed every evening, tie a water bottle to your ankle and kick the leg up, because “strong thighs, strong knees”. Both of them are looking only at the knee.
Treatment guidelines for this kind of pain, however, put hip exercises at the top level alongside exercises for the front of the thigh. The knee is where it hurts. Whether the knee is being pushed out of line with every stride, though, depends partly on the hip and partly on the foot.
What runner’s knee is
The medical name is patellofemoral pain syndrome (patellofemoral pain); runners know it as “runner’s knee”. It is among the five most common injuries in recreational runners (Videbæk and colleagues, 2015; Kakouris and colleagues, 2021).
Walther, author of the Applied Kinesiology textbooks (AK, a way of testing muscle strength by hand to read the state of the body), describes the scene at the rice roll stall quite closely: pain behind the kneecap that often comes on after running a certain distance and can last for hours; climbing stairs, running hills, squatting and kneeling all make it worse. It is most common in new runners who are increasing their distance. He held that the pain comes from increased pressure as the kneecap tracks off-center in the groove between the two femoral condyles (the two bulges of the thighbone at the knee); arthroscopy at this stage has not shown cartilage damage (Walther, Synopsis, p. 465–466).
Many people worry that the knee joint wears out kilometer by kilometer. Pooling the studies, Alentorn-Geli and colleagues (2017) did not find more knee or hip osteoarthritis in recreational runners than in non-runners; in people who had run competitively for many years there was a trend toward more, but the difference was not certain enough to rule out chance (not statistically significant).
A line drawn from the iliac spine
To judge whether the kneecap is easily pulled out of line, musculoskeletal examination textbooks use the Q angle. One line runs from the anterior superior iliac spine, the bony point that sticks out at the front of the hip, down to the middle of the kneecap; the other runs from the tibial tuberosity, where the patellar tendon attaches below the knee, up to the middle of the kneecap. The larger the angle between the two lines, the more the kneecap tends to slide outward. Women usually have a larger angle, because their pelvis is wider.
Right around the kneecap, two muscles pull in opposite directions. The lower fibers of the vastus medialis run obliquely into the inner edge of the kneecap; they are called the vastus medialis oblique (VMO) and pull the kneecap inward. The vastus lateralis pulls it outward. When the vastus medialis works poorly, the kneecap slides outward.
The lower end plays a part too. Prolonged pronation, where the arch of the foot drops inward and does not lift again in time, turns the shinbone inward while the thighbone is turning outward. The knee is twisted between the two directions, and over time this can turn into patellofemoral pain. The Q angle, the pair of muscles pulling in opposite directions and the pronated foot: Walther discusses all three in the few pages he wrote on the knee (Synopsis, p. 465–466).
The hip keeps the pelvis level on one leg
Running means passing your weight from one leg to the other, so at any moment only one leg carries the whole body. During that time, the gluteus medius together with the gluteus minimus on the outer side of the hip are the group that keeps the pelvis stable side to side (Walther, Synopsis, p. 320). When this muscle is weak, a person standing on one leg cannot keep the pelvis level and the opposite hip drops, which textbooks call the Trendelenburg sign; when walking, the pelvis sways too far to the side, giving a waddling gait (Garten, The Muscle Test Handbook, p. 102).
From that anatomy and from the cases we have examined, the clinic’s view is that when the hip cannot hold the pelvis, the thigh has trouble staying on track with each stride, and the knee takes up that misalignment. That is our interpretation; there are no measurements to go with it yet.
The evidence is firmer than the mechanism. The clinical practice guideline on patellofemoral pain from JOSPT, the journal of orthopedic and sports physical therapy (Willy and colleagues, 2019), puts hip strengthening and quadriceps exercises together at the highest level of recommendation. Exercise is also the only approach recommended on its own, without needing to be combined with anything else (Willy and colleagues, 2019; Crossley and colleagues, 2016). Patellar taping sits one level lower. Gait retraining is lower still, and only for people whose movement coordination is off when they run.
So the team captain’s water bottle around the ankle only covers half the job. The other half is exercises for the glutes and the hip abductors (the muscles that move the thigh out to the side). Choosing the exercises, the number of reps and the load is the job of the person coaching your exercises; your part is to tell them where the knee hurts and how many points it reaches on the scale in the section below.
Three numbers after every long run
Physical therapists score pain on a scale of 0 to 10, where 0 is no pain and 10 is the worst pain you can imagine. The Grieve’s textbook considers pain at 0–2 during exercise safe, and up to 5 still acceptable if it is only brief (Grieve’s Modern Musculoskeletal Physiotherapy, p. 573). The clinic applies the same scale to running.
You record it three times: one number during the run, one right after, and one the next morning as you walk down the stairs. The last number is the most honest, and Grieve’s sets its condition there too: the next morning the knee must not hurt more than the day before. If it goes up, the last session was too much for the knee, so shorten the next one. During a flare-up, run less and choose flat routes; if it is bad, stop running for a while and swim to keep your endurance (Walther, Synopsis, p. 466).
When retraining running form, Joyce and Lewindon (2016) advise raising your step rate little by little, about 2–3 more steps per minute than your current rate, with someone guiding you. Increasing step rate by 5–10% reduces the load on the knee and hip (Heiderscheit and colleagues, 2011). That reduction was measured in the lab, not in numbers of injuries, so people without pain do not need to change.
Low plastic stools and hundreds of stone steps
In early spring, many families go to pray at mountain pagodas, climbing hundreds of stone steps. On ordinary days there is squatting to sort vegetables and kneeling to wash the floor. Climbing steps, squatting and kneeling are all among the activities Walther lists as pressing the kneecap hard against the thighbone. You don’t need to give up the New Year pilgrimage. While the knee is sore, choose a higher seat, rest between flights of steps, and keep 0–2 as your marker.
Testing the vastus medialis and gluteus medius at the clinic
At the clinic, the doctor examines you with AK, that is, testing muscle strength by hand. For pain around the kneecap, two muscles are tested first.
The first is the vastus medialis. Travell and Simons call it the “giving-up” muscle, because when it is weak, the knee often feels as if it is about to buckle; patients describe walking normally and suddenly feeling the leg is about to collapse (cited by Walther, Synopsis, p. 467). In AK practice, Walther found that a weak vastus medialis often shows up right at the first examination of people with knee pain. The muscle is still big but does not hold the leg firmly when the doctor pushes to test it; Cuthbert calls this a muscle working below threshold, that is, one that weakens on muscle testing (p. 108).
A common culprit is the muscle spindle. This small structure inside the muscle tells the nervous system whether the muscle is long or short; when it reports wrongly, the central nervous system cannot set the muscle’s activity correctly (Walther, Synopsis, p. 60). When you place your own hand on the exact area of the faulty spindle (AK calls this step therapy localization), the weak, painful muscle may retest strong and pain-free (p. 467).
The second is the gluteus medius, the muscle that keeps the pelvis level from the section above. Garten notes a detail: when the piriformis (a small muscle deep in the buttock) is in spasm and presses on the superior gluteal nerve, the gluteus medius weakens, but often this only shows when it is tested lying on the back, while the classic side-lying test still looks fine (Garten, The Muscle Test Handbook, p. 104). That is why the doctor tests in several positions, including while you stand on one leg.
The knee itself can also drag muscles down. In an observation by Blaich that Walther recorded, stretching the ligaments of the problem knee weakened only the muscles that cross the knee; when the patient placed a hand on the adrenal reflex point (therapy localization), that weak response disappeared. The same page reminds us that an athlete’s adrenal glands are under a lot of stress from the excitement and demands of competition (Walther, Synopsis, p. 465). So the doctor also asks about your race season, performance pressure and sleep.
Walther’s muscle–organ table, which pairs each muscle with an organ inside the body, puts the quadriceps with the small intestine, with vitamin D and the B vitamins as the nutrients that often go with it, and the gluteus medius with the reproductive organs, with vitamin E (Synopsis, p. 313, 320). He uses the quadriceps itself as an example of the table’s limits: it can be weak because of a problem in the muscle while the small intestine is completely normal, so the table only has value alongside other diagnostic methods (p. 14). The clinic uses the table to know what else to test. You taste a little of the nutrient on your tongue, without swallowing, and the doctor retests the muscle. If the muscle gets stronger, it is checked further with lab tests when needed; nothing is prescribed at this step.
Only once the cause is found is it treated at that spot: reactivating the signal at the vastus medialis spindle, stimulating the neurolymphatic reflex points when needed, and mobilizing the pelvis or foot in the direction shown by challenge (the doctor gently pushes the joint in each direction and retests the muscle). For every case of kneecap pain, Walther advises correcting faults in the pelvis and foot (p. 467). At the end of the session, the doctor has you step up onto a high step and retests, to see whether the muscle holds when the knee carries weight. Knee examination, imaging when indicated and the hip–quadriceps exercise program all keep their place. Muscle testing helps make sure the exercises have a muscle that is actually working to train.
The Niu xi – Yi yi ren pair for the knee
The traditional healer (lương y) Nguyen Huu Duc pairs Niu xi (Achyranthes root) with Yi yi ren (Coix lacryma-jobi seed) as “a good pair for the knee” (Core Vietnamese Herbal Remedies, 2017, p. 144). When the knee feels heavy, slightly swollen and warm, hurts more with movement, and the tongue has a yellow, greasy coating, traditional medicine classes this as damp-heat (湿热 / 濕熱, shī rè; dampness and heat that have stagnated) pouring down into the knee. The approach is a modified version of the Si Miao formula (四妙, Four Marvels; “modified” meaning herbs are added or removed for each person), which contains both of those herbs (Chinese Medical Formulas, 方剂学 / 方劑學, p. 325–326). It is prescribed only after joint infection, gout, and meniscus and ligament injuries have been ruled out.
Simple patellofemoral pain is mostly not swollen and warm like that; in that case the doctor determines the traditional medicine pattern from the runner’s overall condition and then prescribes a decoction in 50 ml pouches. We have not found any trial using decoctions for kneecap pain in runners, so the pouches only go alongside the exercises.
Niu xi is not used during pregnancy; if you are trying to conceive, tell the doctor so the herb can be swapped. Si Miao contains Huang bai (Phellodendron bark), an herb to weigh carefully for anyone about to run a race with doping tests.
When to see a doctor
Pain around the kneecap can usually wait for an appointment, except in these cases:
- Pain concentrated at one point on the kneecap bone that is tender to press and gets worse with each session or hurts through the night, because bone injuries from overload in the kneecap are among those that heal poorly (Joyce and Lewindon, 2016);
- A swollen, hot, red knee, especially when you can’t remember any knock or hard run;
- A knee that locks and cannot straighten, or gives way badly enough to make you fall;
- Pain that starts after twisting the knee, a fall or a knock on the trail;
- You have kept the pain within 0–2 and shortened your runs, yet the knee still hurts again on every long run.
In the first four cases, stop running and see a doctor before deciding anything else.
Next Sunday morning at the rice roll stall, you can ask for a taller stool. Keep the water bottle around the ankle, and add the hip exercises your coach chooses. Your phone has one more note: three numbers for each long run. The one you will look at most closely is the next-morning number.
If pain around the kneecap keeps following you from one long run to the next, book an appointment. Dr. Dinh Ngoc Duc (MD, MSc in Traditional Medicine) examines the knee first and refers you on wherever imaging or a specialist is needed. Only then does he move on to the vastus medialis, gluteus medius, pelvis and foot, to find out what the knee is carrying the load for. Book a consultation.
Worth keeping
- Keep pain around the kneecap at 0–2 out of 10 during exercise and running; up to 5 is acceptable only if it is brief and the next morning is no worse;
- After every long run, score the pain the next morning as you walk down the stairs;
- Train both the hip muscles and the front of the thigh, with exercises your coach chooses to match your pain level;
- During a flare-up, shorten your runs, run on flat ground and cut down on hills; to keep your endurance, swim;
- Squat less, avoid very low seats and long kneeling while the knee is sore;
- Pain at one point on the kneecap bone, a swollen and hot knee, or a knee that locks: stop running and see a doctor.
References
Sources in Vietnamese
- Nguyễn Hữu Đức. 2017. Các bài thuốc Nam gốc (bài giảng). Tr. 144.
Sources in English
- Alentorn-Geli E, Samuelsson K, Musahl V, Green CL, Bhandari M, Karlsson J. 2017. The Association of Recreational and Competitive Running With Hip and Knee Osteoarthritis: A Systematic Review and Meta-analysis. J Orthop Sports Phys Ther. 47(6):373-390. doi:10.2519/jospt.2017.7137. PMID: 28504066.
- Crossley KM, van Middelkoop M, Callaghan MJ, Collins NJ, Rathleff MS, Barton CJ. 2016. 2016 Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 2: recommended physical interventions (exercise, taping, bracing, foot orthoses and combined interventions). Br J Sports Med. 50(14):844-52. doi:10.1136/bjsports-2016-096268. PMID: 27247098.
- Cuthbert S. 2013. Applied Kinesiology: Clinical Techniques for Lower Body Dysfunctions. Gangasas. p. 108.
- Garten H. 2013. The Muscle Test Handbook: Functional Assessment, Myofascial Trigger Points and Meridian Relationships. Edinburgh: Churchill Livingstone Elsevier. p. 102–104.
- Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. 2011. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc. 43(2):296-302. doi:10.1249/MSS.0b013e3181ebedf4. PMID: 20581720.
- Joyce D, Lewindon D, editors. 2016. Sports Injury Prevention and Rehabilitation: Integrating Medicine and Science for Performance Solutions. London: Routledge. p. 230, 355.
- Jull G, Moore A, Falla D, Lewis J, McCarthy C, Sterling M, editors. 2015. Grieve’s Modern Musculoskeletal Physiotherapy. 4th ed. Edinburgh: Elsevier. p. 573.
- Kakouris N, Yener N, Fong DTP. 2021. A systematic review of running-related musculoskeletal injuries in runners. J Sport Health Sci. 10(5):513-522. doi:10.1016/j.jshs.2021.04.001. PMID: 33862272.
- Videbæk S, Bueno AM, Nielsen RO, Rasmussen S. 2015. Incidence of Running-Related Injuries Per 1000 h of running in Different Types of Runners: A Systematic Review and Meta-Analysis. Sports Med. 45(7):1017-26. doi:10.1007/s40279-015-0333-8. PMID: 25951917.
- Walther DS. 2000. Applied Kinesiology: Synopsis. 2nd ed. Pueblo (CO): Systems DC. p. 14, 60, 312–313, 320, 465–467.
- Willy RW, Hoglund LT, Barton CJ, Bolgla LA, Scalzitti DA, Logerstedt DS, et al. 2019. Patellofemoral Pain. J Orthop Sports Phys Ther. 49(9):CPG1-CPG95. doi:10.2519/jospt.2019.0302. PMID: 31475628.
Sources in Chinese
- 李冀, 连建伟, 主编. 方剂学. 第 325–326 页.
