Essential knee terminology
Sag sign search for term

The sag sign indicates a possible incompetency of the posterior cruciate ligament.

Sagittal plane search for term

The sagittal plane is the plane of a body 'slice' in a front to back direction.

Saphenous nerve search for term

The saphenous nerve is the nerve branching off from the larger femoral nerve, and which transmits sensation on the inner aspect of the leg. 

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

Scaffold search for term

A scaffold in orthopaedics is a framework that is used to facilitate regenerating a damaged tissue or bone.

Schatzker classification search for term

The Schatzker classification is a visual system for the classification of tibial plateau fractures types I - VI.

Schenck Classification search for term

The Schenck Classification gives an idea of the degrees of knee dislocation based on the number of ligaments damaged, and the presence of associated fractures.

Screw home mechanism search for term

The screw home mechanism is a movement of the joint that is key to keeping the knee stable while standing upright.

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

Second look arthroscopy search for term

A 'second look' arthroscopy is when a patient is pro-actively booked to have an arthroscopy just to check up on a previous surgical procedure.

Segond Fracture search for term

A Segond Fracture is an avulsion of a small chip of bone off the lateral side of the femur, commonly seen in association with an anterior cruciate ligament rupture. 

Semi-lunar cartilage search for term

A semi-lunar cartilage is the old-fashioned name for a meniscus. 'Semi-lunar' means 'half-moon' and refers to the shape of the meniscus.

Semimembranosus search for term

The semimembranosus muscle is one of the three hamstrings muscles.

Semitendinosus search for term

The semitendinosus muscle is one of the hamstrings muscles.

Semitendinosus graft search for term

A semitendinosus graft is a transplant derived from the tendon of the semitendinosus muscle.

Semitendinosus tenodesis search for term

Semitendinosus tenodesis is one of several surgical procedures to improve knee stability.

Septic arthritis search for term

Septic arthritis in deep infection within the knee joint. It is a dreaded complication of knee injury or surgery.

Sherman Classification search for term

The Sherman classification identifies the positioning of an anterior cruciate ligament (ACL) tear.

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

Shin bone search for term

The shin bone larger bone of the lower leg, correctly called the 'tibia'.

Short arc extensions search for term

Short arc extensions are knee rehabilitation exercises to re-trigger quads activity.

Side-stepping search for term

Side-stepping is a knee rehabilitation exercise to improve hip abduction.

Single Stage Autologous Chondrocyte Implantation search for term

Single Stage Autologous Chondrocyte Implantation (STACi) is a one-step surgical cartilage repair procedure.

Single-bundle ACL graft search for term

A single-bundle ACL graft is a reconstruction of the anterior cruciate ligament using a 'single-bundle' of graft material as opposed to a 'double-bundle'. 

Single-photon-emission computed tomography search for term

Single-photon-emission computed tomography is a radioactive imaging technique to give information about blood flow in the body.

Slocum test search for term

The Slocum test is a modification of the anterior drawer test and assesses the integrity of the anterior cruciate ligament.

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

Small-incision knee replacement search for term

A small-incision knee replacement is a knee replacement performed with a smaller incision than traditionally, and using special techniques and instruments.

Snapping search for term

Snapping is a knee symptoms where the patient experiences a sharp noisy snap of structures usually at the outer side or back of the knee.

SPECT search for term

SPECT is an abbreviation of 'single-photon-emission computed tomography'.

Sports therapist search for term

A Sports Therapist is a healthcare professional specifically concerned with the prevention of injury and the rehabilitation of the patient back to optimum levels of functional, occupational and sports specific fitness.

SPP search for term

SPP is an abbreviation of 'suprapatellar plica'.

Spurs search for term

Spurs are small and sometimes sharp abnormal bony outgrowths at the joint edges, usually associated with osteoarthritis.

Squats search for term

Squats are knee rehabilitation exercises - with your arms out in front of you, bending as if you are going to sit, but then straightening up again.

Squinting patellae search for term

Squinting patellae is when the two kneecaps face towards each other despite the patient standing comfortably with the feet facing forwards.

STACi search for term

STACi is an abbreviation of Single Stage Autologous Chondrocyte Implantation.

Standing wall slides search for term

Standing wall slides are knee rehabilitation exercises to improve flexion and strengthen the quads muscles.

Staple search for term

Staples for ACL graft fixation are made of cobalt chrome with two sharp leg spikes for easier penetration into the bone without predrilling.

Static bicycle search for term

A static bicycle is an exercise bicycle on a stand, where the wheels turn but the bicycle stays still.

Static quads search for term

Static quads are very early knee rehabilitation exercises to activate the quadriceps muscle of the lap.

Stem cell search for term

A stem cell is an unspecialised cell with a remarkable ability to divide over and over and become differentiated into another type of cell, replacing damaged body tissue.

Stem cell line search for term

A stem cell line is a commercial culture of stem cells all derived from the same original cell source, which has been allowed to multiply.

Stem cells search for term

Stem cells are unspecialised cells with a remarkable ability to reproduce and become differentiated into another type of cell, replacing damaged body tissue.

Step ups search for term

Step ups are knee rehabilitation exercises for rebuilding early quadriceps muscle strength.

Steroids search for term

Steroids used in orthopaedics are hormonal drugs used to suppress inflammation.

Stiff knee search for term

Knee stiffness can be a result of fluid in the joint, adhesions or scar tissue in the tissue folds, bony deformity or other mechanical obstructions.

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

Straight leg raise search for term

A straight leg raise is knee rehabilitation exercise to strengthen the quads muscles, but it is also used by surgeons to give a quick idea of the activity of the quads after surgery.

Stromal vascular fraction search for term

Stromal vascular fraction is the name given to a portion of tissue extracted by enzymes from microfragmented fat

Stutter test search for term

The stutter test is a test for the presence of a symptomatic medial synovial plica in the knee.

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

Subchondral search for term

The word 'subchondral' is an adjective referring to the layer of bone immediately under the articular cartilage.

Subchondral drilling search for term

Subchondral drilling is a surgical procedure where small holes are drilled through damaged joint cartilage into the bone marrow of the underlying bone.

Subluxation search for term

Subluxation is when the bones of a joint nearly dislocate, but not quite, and then return to a normal position, eg patellar subluxation.

Sudek's atrophy search for term

Sudeck's atrophy is an old term to describe tissue wasting secondary to complex regional pain syndrome.

Sulcus angle search for term

The sulcus angle is a measurement of the steepness of the walls of the groove in which the kneecap rides (the trochlear groove).

Superficial peroneal nerve search for term

The superficial peroneal nerve is the superficial branch of the common peroneal nerve.

Superior search for term

Superior is a positional word, meaning 'above'.

Suprapatellar search for term

Suprapatellar is a positional adjective describing something to be 'above the patella' (kneecap).

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

Suprapatellar bursa search for term

The suprapatellar bursa is an extension of the joint cavity above the kneecap.

Suprapatellar plica search for term

A suprapatellar plica is a membrane - possibly an embryonic remnant - that stretches across the joint cavity in the pouch above the kneecap.

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

Suprapatellar pouch search for term

The suprapatellar pouch (suprapatellar recess) is the extension of the knee joint cavity above the patella (kneecap).

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

Surface replacement search for term

A surface replacement involves an implant usually used on the surface of the condyles (end of the femur) or for the damaged kneecap and groove in which the kneecap (patella) runs.

SVF search for term

SVF is an abbreviation of Stromal Vascular Fraction.

Swelling search for term

Swelling of the whole knee or a region of the knee is typically a result of an accumulation of fluid.

Sympathetic nervous system search for term

The sympathetic nervous system is the nerve system that controls things like heart rate and blood pressure.

Symptom search for term

A symptom is a discomforture felt by the patient - for example pain, giving way, catching.

Syndrome search for term

A syndrome is a collection of signs and symptoms often found in association with one another.

Synovectomy search for term

Synovectomy is a surgical procedure to remove excessive joint lining (synovium).

Synovial chondromatosis search for term

Synovial chondromatosis is a rare disorder where the joint lining (synovium) proliferates and produces a benign proliferation of synovial tissue and bits of cartilage.

Synovial fluid search for term

Synovial fluid is the fluid lubricating the inside of any synovial joint, and it is secreted by the synovium (the cells of the joint lining).

Synovial joint search for term

Synovial joints are movable joints that contain a lubricating fluid called synovial fluid and have articular cartilage to keep the ends of the moving bones separate from each other.

Synovial membrane search for term

The synovial membrane is the cellular lining around the inside of lubricated joints.

Synovial plica search for term

A synovial plica is an infold of the joint lining or synovium - it is a normal anatomical structure but can sometimes become problematic.

Synovitis search for term

Synovitis is inflammation of the joint lining (synovium).

Synovium search for term

The synovium is the cell layer that constitutes the inner lining of the knee joint and other joints.

Synthetic graft search for term

A synthetic graft is a graft using artificial materials, eg Gore-Tex for cruciate ligament reconstruction.