Essential knee terminology
Pain in the back of the knee search for term

Pain in the back of the knee is common, and may have a number of causes, because the back of the knee is structurally complex.

Pain score search for term

A pain score is a scoring system used by doctors to 'measure' pain.

Parapatellar search for term

Parapatellar means 'along the sides of the kneecap'.

Parapatellar recesses search for term

Parapatellar recesses are the anatomical 'gutters' alongside the patella or kneeap.

Parrot-beak tear search for term

A parrot-beak tear of the meniscus is an oblique tear of the knee meniscus where the torn end rounds off to resemble a parrot's beak.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Partial knee arthroplasty search for term

A partial knee arthroplasty replaces part of the knee joint with an implant.

Partial knee replacement search for term

A partial knee replacement (or unicompartmental knee replacement) replaces one region (compartment) of the knee with a metal and plastic implant.

Partial meniscal replacement search for term

Replacing an irreparably-damage portion of meniscus with a tissue-engineered one, such as a collagen meniscus.

Partial meniscectomy search for term

A partial meniscectomy is the removal of a part of a meniscus.

Passive extension search for term

Passive extension is a knee rehabilitation exercise (stretch).

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Paste graft search for term

A paste graft is a technique of cartilage repair, using morcelised cartilage.

Patella search for term

The patella is the kneecap, the bone sitting over the front of the knee. Plural = 'patellae'.

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Patella alta search for term

In patella alta the kneecap rides too high up on the femur (thigh bone). This may make it liable to sublux or even dislocate.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Patella baja search for term

Patella baja is a kneecap that is positioned abnormally low in relation to the groove of the femur. It is also known as patella infera or infrapatellar contracture syndrome.

Page content approved November 2023 by Dr Lars Blond (Knee Surgeon)

Patella infera search for term

In patella infera the kneecap (patella) rides too low down the femur (thighbone).

Patella stabilisation search for term

Patellar stabilisation methods include braces and surgery to reduce the tendency of the patella to sublux or dislocate sideways out of its underlying groove.

Patellae search for term

Patellae is the plural of 'patella'.

Patellar search for term

Patellar is the adjective to describe things related to the patella.

Patellar alignment search for term

Patellar alignment is the position of the kneecap relative to the groove in the underlying femur bone into which it slides when the knee is bent and straightened.

Patellar apprehension test search for term

The patellar apprehension test is performed to confirm the doctor's suspicion of an underlying patellar instability, such as patellar subluxation or dislocation.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Patellar brace search for term

A patellar brace is a knee brace designed to stabilise or protect the kneecap.

Patellar clunk search for term

A patellar clunk is an uncomfortable clunk noise (and feeling) around the patella, usually associated with certain types of knee replacement, and due to scarring above the patella.

Page updated July 2023 by Dr Sheila Strover (Clinical Editor)

Patellar dislocation search for term

Patellar dislocation is a painful and distressing event, when the patella jumps clean out of the restraining walls of the groove in which it normally rides.

Page updated December 2023 by Dr Sheila Strover (Clinical Editor)

Patellar dysplasia search for term

Patellar dysplasia means an abnormally-shaped patella.

Page updated October 2023 by Dr Sheila Strover (Clinical Editor)

Patellar fracture search for term

A patellar fracture is a traumatic break of the patella bone (knee cap).

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Patellar instability search for term

Patellar instability is when the kneecap does not ride smoothly throughout its excursion in the underlying groove of the femur, popping over to one side, or even de-railing.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Patellar malalignment search for term

Patellar malalignment is present when the kneecap - for whatever reason - does not sit optimally in the underlying groove as the knee bends and straightens. 

Patellar mobilisations search for term

Patellar mobilisations are soft tissue stretches around the kneecap that prevent adhesions from tethering it down and causing a stiff knee.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Patellar resurfacing search for term

Patellar resurfacing is a surgical procedure to replace the joint surface of the patella.

Patellar retinaculum search for term

The patellar retinaculum is the fibrous material at the sides of the patella, that act to stabilise it.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Patellar subluxation search for term

Patellar subluxation is when the patella rides suddenly up the side of its groove, but does not fully dislocate.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Patellar tendinitis search for term

Patellar tendinitis is a painful condition of the patellar tendon where tiny tears within the tendon attempt to heal themselves but lead to foci of mucoid deterioration within the tendon.

Patellar tendinopathy search for term

Patellar tendinopathy is a degenerative disorder of the patellar tendon.

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Patellar tendon search for term

The patellar tendon is the broad tendon under the kneecap, joining it to the tibia (shin).

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Patellar tendon rupture search for term

A patellar tendon rupture is a partial or complete breaking of the patellar tendon under the kneecap.

Patellar tilt search for term

Patellar tilt is when the patella is tilted to one side, generally the lateral (outer) side, secondary to tightness in the lateral retinaculum, the fibrous restraint at the lateral side of the patella.

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Patellar tilt test search for term

The patellar tilt test assesses the amount of patellar tilt which can be elicited by an examiner, and gives an idea of the tightness of the retinaculum on each side of the patella.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Patellar tracking search for term

Patellar tracking is the gliding of the patella within the underlying groove of the femur bone.

Patellectomy search for term

Patellectomy is a surgical procedure where part or all of the patella bone is cut out.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Patellofemoral search for term

'Patellofemoral' means that area of the knee where the kneecap (patella) is in contact with the thighbone (femur).

Patellofemoral arthritis search for term

Patellofemoral arthritis is osteoarthritic joint cartilage destruction of the patellofemoral joint - either the patella, or the trochlear groove, or both.

Patellofemoral dislocation search for term

Patellofemoral dislocation is when the patella jumps completely out of the walls of the groove in the femur bone, making the joint look horribly deformed.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Patellofemoral instability search for term

In patellofemoral instabilty the patella (kneecap) changes its relationship to the groove of the femur bone (thighbone) and may partially or fully de-rail.

Patellofemoral joint search for term

The patellofemoral joint is the contact area between the undersurface of the patella and the groove of the femur bone.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Patellofemoral pain syndrome search for term

Patellofemoral pain syndrome is a group of symptoms related to the joint between the kneecap (patella) and its underlying groove in the femur bone, as well as the soft tissues related to the patella, such as the fat pad.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Patellofemoral resurfacing search for term

Patellofemoral resurfacing is a partial knee replacement involving the areas of both patella and femur where they come into contact.

Patellofemoral subluxation search for term

Patellofemoral subluxation is when the patella briefly jumps almost out of the walls of the groove in the femur bone, but then returns to its normal position.

Patellofemoral syndrome search for term

Patellofemoral syndrome is pain experienced around the kneecap and which may be caused by a combination of several possible factors.

Patellotrochlear engagement index search for term

This seems to have gotten lost

Patellotrochlear engagement index search for term

The patellofemoral engagement index is a measurement derived from MRI images and which gives an idea of the degree of patella alta in patients with recurrent instability.

Pathophysiology search for term

Pathophysiology is the disordered body processes associated with disease or injury.

PCL search for term

PCL is an abbreviation of 'posterior cruciate ligament'.

PCP search for term

PCP is an abbreviation of 'primary care physician'.

PE search for term

PE is an abbreviation of 'pulmonary embolus'.

Peer review search for term

A medical publication that has passed peer review is one that has been carefully evaluated by other doctors who are expert in the same field.

Peri-articular search for term

Peri-articular means 'around the joint'.

Periosteum search for term

The periosteum is the thin web-like covering of fibrous tissue around the outside of bones.

Peroneal nerve search for term

The peroneal nerve is a branch of the sciatic nerve that supplies movement and sensation to the lower leg.

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Pes anserine bursa search for term

The pes anserine bursa is a sac (lined space) under the attachments of the pes anserine tendons on the inner aspect of the knee.

Pes anserine bursitis search for term

Pes anserine bursitis is inflammation of the pes anserine bursa.

Pes planus search for term

Pes planus is the same as flat foot.

Pes tendons search for term

The pes tendons are the attached tendon of the sartorius, gracilis and semitendinosus muscles, which insert together on the upper tibia on the medial side of the knee.

PFPS search for term

PFPS is an abbreviation of 'Patellofemoral pain syndrome'.

PFS search for term

PFS is an abbreviation of 'patellofemoral syndrome'.

Physes search for term

Physes are the growth plates of bones in children.

Page updated July 2023 by Dr Sheila Strover (Clinical Editor)

Physical therapist search for term

A physical therapist is a clinician specialising in rehabilitation.

Physiotherapist search for term

Physiotherapy is a health care profession concerned rehabilitation; musculoskeletal physiotherapy (MSK) deals with human function and movement and maximising potential.

Physis search for term

The physis is the growth plate near the end of bones, from which the new bone cells develop.

Pie-crusting search for term

Pie-crusting is a surgical technique where tiny holes are deliberately poked into a ligament to allow it to stretch more than usual.

Pigmented villonodular synovitis search for term

Pigmented villonodular synovitis (PVNS) is an unusual condition of the lining inside the knee joint, where the synovial cells are abnormally laden with a brown pigment.

Piriformis muscle search for term

The piriformis is a muscle in the buttock.

Piriformis stretch search for term

A piriformis stretch is a knee rehabilitation exercise (stretch) to loosen the piriformis muscle and tendon.

Piriformis syndrome search for term

The piriformis syndrome is buttock pain due to tightening or irritation of the piriformis muscle where it is crossed by the sciatic nerve.

Pivot shift test search for term

The pivot shift test is a test to assess the integrity of both the anterior cruciate ligament and and also the other key structures that contribute to the knee's stability.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

PKR search for term

PKR is an abbreviation of 'partial knee replacement'.

Placebo search for term

A placebo is a dummy drug used in clinical trials.

Platelet Rich Plasma search for term

Platelet Rich Plasma is a blood preparation where a portion of plasma rich in platelets is extracted from the rest of the blood.

PLC search for term

PLC is an abbreviation of 'posterolateral corner', that region at the side of the knee towards the back.

Plica search for term

A plica is a ribbon-like fold of joint lining (synovium) which may be present in any knee as an embryological remnant.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Plica surgery search for term


Plica surgery in the knee is performed to remove a plical fold of joint lining that is being troublesome, perhaps because it is catching in the joint.

Plica syndrome search for term

Plica syndrome is a collection of symptoms commonly experienced together when a fold of joint lining called a plica is irritated, thickened and intermittently catches in the joint.

Page updated November 2023 by Dr Sheila Strover (Clinical Editor)

Pluripotent search for term

Pluripotent - referring to stem cells - a cell that has the capacity to differentiate into any cell type within the three main tissue groups of the body.

Polyarthropathy search for term

Polyarthropathy means joint problems - such as inflammation - affecting several joints.

Polyethylene search for term

Polyethylene is a variety of plastic.

Polymer search for term

A polymer is a long chain molecule used for making plastics.

Popliteal search for term

Relating to the popliteal area, ie the recess at the back of the knee.

Popliteal cyst search for term

A popliteal cyst is a fluid-filled lump at the back of the knee.

Popliteal fossa search for term

The popliteal fossa is the indented area at the back of the knee.

Popliteofibular ligament search for term

The popliteofibular ligament connects the popliteus tendon to the top of the fibular bone, in the area at the back of the knee known as the posterolateral corner.

Popliteomeniscal fascicles search for term

The popliteomeniscal fascicles are small but important connections between the popliteus muscle and tendon and the back of the lateral meniscus.

Popliteus muscle search for term

The popliteus muscle is a small but important muscle at the back of the knee.

Page updated September 2023 by Dr Sheila Strover (Clinical Editor)

Popliteus tendinitis search for term

Popliteus tendinitis is an overuse condition, where the attachment of the popliteus tendon to the lateral femoral condyle (bone on the outer side of the knee) becomes painful.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Popliteus tendon search for term

The popliteus tendon is the tendon of the popliteus muscle, which is a muscle at the back of the knee. 

Popliteus tendonitis search for term

Popliteus tendonitis is the same condition as 'popliteus tendinitis', but the latter is the more accepted spelling.

Portal search for term

A portal in the knee is the small cut made by the surgeon during arthroscopy, to allow the passage of the instruments.

Portal scar search for term

A portal scar is a small scarred area related to an arthroscopic portal - the small hole the surgeon makes to inserts the arthroscopy instruments.

Posterior search for term

Posterior is a positional word meaning 'behind'.

Posterior capsulotomy search for term

A posterior capsulotomy or posterior capsular release is a surgical procedure to release scar tissue within the folds of the capsule at the back of the knee.

Page updated July 2023 by Dr Sheila Strover (Clinical Editor)

Posterior cruciate ligament search for term

The posterior cruciate is one of the two cruciate ligaments which are important in stabilising the knee.

Posterior cruciate ligament injury search for term

Posterior cruciate ligament injury may involve an intrasubstance tear (complete or incomplete) or an avulsion from the bone.

Posterior cruciate ligament reconstruction search for term

Posterior cruciate ligament (PCL) reconstruction involves using graft material to refashion and replace a damaged posterior cruciate ligament.

Posterior drawer test search for term

The posterior drawer test assesses the integrity of the posterior cruciate ligament.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Posterior horn search for term

The meniscus is crescentic, with two horns (like a new moon) - and the posterior horn is the one at the back.

Posterior oblique ligament search for term

The posterior oblique ligament is a structure that considered by some to be part of the medial collateral ligament and by others to be a ligament in its own right.

Posterior tibial slope search for term

Posterior tibial slope exists when the top of the tibia slopes downward towards the back of the knee. A few degrees of posterior slope is normal.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Postero-lateral search for term

Postero-lateral is a compound 'positional' word - meaning behind and to the outer aspect.. It is derived from 'posterior' and 'lateral'.

Postero-medial search for term

Postero-medial is a 'positional' word - meaning behind and to the inner aspect. It is derived from 'posterior' and 'medial'.

Posterolateral corner search for term

The posterolateral corner is the region on the outer aspect of the knee, towards the back. The anatomy here is complex, and repair of any damage is the domain of only the expert surgeon.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Posterolateral corner injury search for term

A posterolateral corner injury includes damage to structures at the back of the knee on the outer side.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Posterolateral rotatory instability search for term

Posterolateral rotatory instability is a particular multi-ligament injury involving damage to the structures of the posterolateral corner at the back of the knee.

Posteromedial corner search for term

The posteromedial corner (PMC) is the region towards the back of the knee on the inner side.

Page updated January 2024 by Dr Sheila Strover (Clinical Editor)

Pre-patellar bursa search for term

A pre-patellar bursa is a space between the tissues in front of the knee which is enclosed like an envelope and lined with lubricating cells.

Pre-patellar bursitis search for term

Pre-patellar bursitis is inflammation in the pre-patellar bursa, appearing as a tense swelling in front of the kneecap and discreet from the kneecap bone itself.

PRICE search for term

PRICE is a mnemonic for remembering the rehabilitation regime of Protection, Rest, Ice, Compression, Elevation

Pridie drilling search for term

Pridie drilling is a now defunct cartilage repair procedure that paved the way for microfracture and nanofracture.

Pridie procedure search for term

The Pridie Procedure is a procedure from the 1980s, where damaged joint surface is drilled with a fine drill, to enable stem cells to migrate from the bone marrow underneath and to cover the surface with new fibrocartilage cells.

Primary care physician search for term

A primary care physician is the family doctor.

Primary Repair search for term

A primary repair is a term used in knee surgery, where a structure (eg ligament, meniscus) is repaired rather than reconstructed.

Primary varus search for term

Primary varus are bow legs that the person was simply born with.

Prodrome search for term

The prodrome is the early phase of a medical problem, before the incident is fully apparent but early symptoms have started.

Progenitor cell search for term

A progenitor cell is a stem cell that is already partially differentiated. A stem cell can multiply an infinite number of times, but a progenitor cell can only multiply a certain number of times.

Progenitor cells search for term

Progenitor cells are stem cells that are already partially differentiated.

Prolotherapy search for term

Prolotherapy is the injection of an irritant, usually dextrose, into disturbed soft tissues such as tendons and fascia in an effort to stimulate self regeneration with new cells.

PROM search for term

PROM is an abbreviation for 'Passive Range-of-Motion'.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Prone hangs search for term

Prone hangs are simple rehabilitation stretches to improve knee extension.

Page updated December 2023 by Dr Sheila Strover (Clinical Editor)

Proprioception search for term

Proprioception is the ability to sense the position and movement of a joint in space and it is a key component of balance and knee joint stability.

Prosthesis choice search for term

Total knee replacement requires the surgeon to consider a number of factors when deciding on the type of total knee replacement for any particular patient.

Proximal search for term

Proximal is a positional word, referring to a position closer to the head.

Proximal realignment search for term

Proximal realignment procedures are those surgical procedures performed above the attachment of the kneecap in an attempt to better align it in the groove of the underlying femur bone.

Page updated August 2023 by Dr Sheila Strover (Clinical Editor)

Proximal tibial nerve search for term

The proximal tibial nerve arises from the sciatic nerve just proximal to the knee joint.

PRP search for term

PRP is an abbreviation for 'Platelet Rich Plasma', a concentration of platelets separated from a blood sample by centrifuge.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Pseudo search for term

Pseudo means 'false'. So 'pseudo-locking', for example, is when the knee appears to be stuck in a bent position, but readily unlocks.

Pseudolocking search for term

Pseudolocking is the condition where the knee suddenly is unable to fully extend, but then a little manoeuvre allows it to loosen up and have full range of motion again.

PT search for term

PT is an abbreviation of 'physical therapist'.

Pulmonary embolus search for term

A pulmonary embolus is a blood clot shooting to the lungs, usually from a clot in the leg veins.

PVNS search for term

PVNS is an abbreviation of 'pigmented villonodular synovitis'.

PWB search for term

PWB is an abbreviation for 'partial weight bearing'.

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