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The Tibiofibular Joint and Knee Pain

A neglected joint in the diagnosis of knee pain (and near-knee pain)

Paul Ingraham • 5m read
Anatomical diagram of the proximal tibiofibular joint, bones only.

The proximal tibiofibular joint.

The proximal tibiofibular joint (PTFJ) is just below the knee on the outside of the leg. It is a simple joint that does not move much, just a bit of sliding. It connects the top end of the large shin bone (tibia) to the top end of the much smaller leg bone (fibula) beside it. The tiba and fibula are the two main long bones of the lower leg. (The distal tibiofibular joint is part of the ankle.)

The PTFJ is obscure and unstudied, overshadowed by the exciting knee joint and its many problems, and rarely considered in diagnosis — but it can be an important driver of lateral knee pain, or occasionally mistaken for a shin injury. Occasionally it is mistaken for runners knee, and it could be considered runners knee insofar as it is knee-ish problem that runners sometimes get — but almost all runners knee is either IT band syndrome or patellofemoral pain.

“The human proximal tibiofibular joint mechanics has been largely unknown due to lack of attention by both the clinicians and the anatomists alike.”

Sarma et al., “Proximal tibiofibular joint: Rendezvous with a forgotten articulation”1

A neglected cause of lateral knee pain

Injury to the PTFJ is “an often-forgotten cause of lateral knee pain,”2 and yet the PTFJ is not really a knee joint — it’s just nearby. If the knee was New York, the PTFJ would be Queens. Trauma to the knee can leave the PTFJ untouched, and vice versa. However, dislocation of the PTFJ can sometimes compromise knee joint stability, due to some (variable) shared ligamentous support.

Sometimes patients suffering mainly from PTFJ pain are repeatedly evaluated for knee trouble, even get knee surgery, all without even looking at the PTFJ. It’s surprising how diagnostically neglected this joint is, considering that it is close enough to the knee that it is usually imaged along with the knee.

The PTFJ is not a knee joint … except when it is

The knee and the PTFJ are not always entirely separate joints. In quite a few people — estimates vary from 10 to 60% — they are connected by a tunnel of joint cavity,3 sharing joint fluid. In this case, the PTFJ is a “fourth compartment” of the knee joint.

The main clinical implication is that swelling may be shared. If the knee swells, the PTFJ swells! Injury to either joint could potential change the mechanics of the other — although the knee affecting the PTFJ is probably more likely than the other way around.4

A dislocated proximal tibiofemoral joint. Courtesy of Assoc Prof Craig Hacking,, from the case rID: 39346. This sports injury was caused by twisting.

Symptoms of proximal tibiofibular joint disorders

Symptoms arising from PTFJ mainly are mostly low lateral knee pain, almost low enough to be mistaken for shin pain (but probably not often). Pain in this location is routinely mistaken for common knee injuries, chiefly runners’ knee, and strains of the lateral collateral ligament of the knee.

Injury to the common peroneal nerve around the head of the fibula can also result in tingling or numbness on the top of the foot and/or the side of the leg, and foot drop (the foot slapping down a bit with each step).

Tibiofibular pain versus IT band pain

ITB syndrome is one of the two major kinds of “runner’s knee” (along with patellofemoral pain). It’s a common and notorious injury, a tendinitis or bursitis-like injury on the side of the knee (and not the thigh or hip), and it is the most obvious diagnostic suspect for any lateral knee pain. It’s true that both IT band pain and tibiofibular pain cause “lateral knee pain,” and cause pain in very similar locations, the location of each kind of pain is specific and clear:

  1. Tibiofibular pain is definitely below the knee joint line.
  2. ITBS pain occurs on or just above the joint line, on the big bump of bone on the side of the femur at the knee (lateral epicondyle of the femur).

Also, ITBS always develops insidiuously, while tibiofibular injury is probably mostly traumatic.

Common PTFJ injuries and conditions

The most common issues with the PTFJ are:

The PTFJ may also get “stuck” (hypomobile). This is a plausible pathology, but it has never been formally described. There is just a single published case report of putative hypomobility.5

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter., or subscribe:


  1. Sarma A, Borgohain B, Saikia B. Proximal tibiofibular joint: Rendezvous with a forgotten articulation. Indian J Orthop. 2015;49(5):489–95. PubMed 26538753 ❐ PainSci Bibliography 52026 ❐
  2. Forster BB, Lee JS, Kelly S, et al. Proximal Tibiofibular Joint: An Often-Forgotten Cause of Lateral Knee Pain. American Journal of Roentgenology. 2007;188(4):W359–W366. PainSci Bibliography 52025 ❐
  3. Bozkurt M, Yilmaz E, Atlihan D, et al. The proximal tibiofibular joint: an anatomic study. Clin Orthop Relat Res. 2003 Jan;(406):136–40. PubMed 12579012 ❐
  4. The knee is a much more spacious joint — the largest joint capsule in the body. Plenty of “overflow” room. The PTFJ probably cannot produce enough synovial fluid to significantly affect it.
  5. Beazell JR, Grindstaff TL, Magrum EM, Wilder R. Treatment of lateral knee pain by addressing tibiofibular hypomobility in a recreational runner. N Am J Sports Phys Ther. 2009 Feb;4(1):21–8. PubMed 21509117 ❐ PainSci Bibliography 52021 ❐ This paper describes a diagnosis of hypomobility made based mainly on palpation: the joint just felt stiff, basically. It’s a data point, but we really have no idea if PTFJ hypomobility is a real phenomenon.


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