Anterior Knee Pain: What’s all the hype around the Runner’s and the Jumper’s knee? Part I.
Updated: Nov 30, 2020
There we go. Another lockdown is affecting our daily sports routine, as almost all the gyms are closed around the globe. Over the summer, some of you were studiously building your own home gym, containing smart bike trainers, rowing machines or the omnipresent Peloton trainer. As the ski season opening is currently at high risk, some of you are looking for alternatives, mainly around the mountains. What first comes to mind, is hiking and running. Interestingly, we see an increased number of patients coming to our clinic with anterior knee pain. And let’s be honest. If you ever challenged yourself to a long-running distance, you know that anterior knee pain can be a true motivation killer. We will explain to you all the fuss around anterior knee pain, and how you can avoid being a long-term patient.
As you may know, the knee is one of the most complex joints in your body. Complex interaction between muscles, ligaments, capsule, bony structures, and menisci are needed to provide a biomechanical stable system ensuring optimal function. So, let’s start with some simplified anatomy in the First Part of the review: (Part I).
The thighbone (femur), the underside of the kneecap (patella), and the upper end of the shinbone (tibia) are covered by articular cartilage and a thin layer of tissue (=synovium) which ensures a smoothly gliding against each other. The menisci, which are located medially and laterally in the joint, withstand many different forces within the knee and play a crucial role in loadbearing and shock absorption. (Kohn and Moreno 1995, Allaire, Muriuki et al. 2008, Willinger, Lang et al. 2019) Simplified, the meniscus tissue is wedge-shaped, which is needed to stabilize the curved femoral condyle during active motion with the flat tibial plateau. (Hoshino and Wallace 1987, Makris, Hadidi et al. 2011) Additionally, a small pad of fat (e.g. Hoffa Pad) is located just underneath the patella behind the patellar tendon, which is supposed to act as a shock absorber by cushioning the patella. As you will later see, this small tissue of fat will play an important role in what we think causes anterior knee pain.
When scanning current literature, you will probably see hundreds of studies investigating the reasons for anterior knee pain. One of the most common reasons is overuse while jogging (especially downhill!), excessive hiking, climbing stairs, or squatting. Most of our patients present after a sudden change in physical activity, especially CrossFitters, when preparing for the next challenge. In some patients, changes in footwear or the use of wrong sports training techniques can be a cause for anterior knee pain. Nowadays, we encounter many patients, who have no pain while hiking upwards, but who have increased pain while climbing downstairs. This is often related to increased weight-bearing of the joint and fatigue of the upper limb musculature. As such, you may feel anterior knee pain as a consequence of increasing intra-articular pressure. This may lead to acute inflammation of the surrounding tissue, mostly, of the Hoffa pad, which may be painful. In the long term, this could enhance hypertrophy of the fatty tissue, leading to an impingement of the fat pad during active motion of the knee.
Additionally, some patients may also present with softening and breakdown of the articular cartilage of the patella. The so-called “chondromalacia patella” can lead to chronic, painful inflammation of the synovium. As softening of the cartilage also leads to increased loads and pressure within the underlying bone, bony edema (known as a bone bruise) may occur, which is also known to be a source of significant pain.
The last condition, which we often encounter within this patient cohort, are muscular imbalances, weaknesses, or a lack of mobility, especially in the quadriceps muscle group and in the hip. These conditions are known to be a source of anterior knee pain, as increased pressure between the back of the patella and the trochlea results, may ending in alteration of the cartilage. Additionally, some patients do also complain about patellar malalignment, which, simplified, means that abnormal tracking of the patella in the groove leads either to lateralizing of the patella, or to a high riding patella (=Patella Alta) during knee flexion. Similar to the condition described above, increased pressure between patella and trochlea may be expected leading to irritations of the surrounding tissues.
Alright, let's go to Part II.
Allaire, R., M. Muriuki, L. Gilbertson and C. D. Harner (2008). "Biomechanical consequences of a tear of the posterior root of the medial meniscus: similar to total meniscectomy." J Bone Joint Surg Am 90(9): 1922-1931.
Hoshino, A. and W. A. Wallace (1987). "Impact-absorbing properties of the human knee." J Bone Joint Surg Br 69(5): 807-811.
Kohn, D. and B. Moreno (1995). "Meniscus insertion anatomy as a basis for meniscus replacement: a morphological cadaveric study." Arthroscopy 11(1): 96-103.
Makris, E. A., P. Hadidi and K. A. Athanasiou (2011). "The knee meniscus: structure-function, pathophysiology, current repair techniques, and prospects for regeneration." Biomaterials 32(30): 7411-7431.
Willinger, L., J. J. Lang, C. von Deimling, T. Diermeier, W. Petersen, A. B. Imhoff, R. Burgkart and A. Achtnich (2019). "Varus alignment increases medial meniscus extrusion and peak contact pressure: a biomechanical study." Knee Surgery, Sports Traumatology, Arthroscopy: 1-7.