[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Lower limb](https://durgical.com/en/anatomy/region/lower-limb/) › Semitendinosus tendon [Muscular system](https://durgical.com/en/anatomy/system/muscular-system/) · [Lower limb](https://durgical.com/en/anatomy/region/lower-limb/) # Semitendinosus tendon The semitendinosus tendon is a long, round hamstring tendon on the inner back of the knee; it is a common graft to rebuild the ACL. Official name: Tendon of semitendinosus [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=lower_limb&select=semitendinosus_tendon&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A long, thin hamstring tendon on the inner back of the knee, ending on the inner [tibia](https://durgical.com/en/anatomy/tibia/). ## What it does Helps bend the knee and turn the shin inward; supports the knee from the inner side. ## Key points - The most prominent cord at the back of the inner knee; its long round tendon makes it the first-choice hamstring autograft, often folded into four strands - Accessory bands from the tendon to the fascia of the [medial head of gastrocnemius](https://durgical.com/en/anatomy/medial-head-of-gastrocnemius/) are common: they are cut before stripping, or the stripper cuts the graft short - With the semimembranosus it forms the upper medial border of the popliteal fossa ## Key facts **Attaches** Long round tendon (lower half of the muscle) to the pes anserinus on the upper medial tibia, the lowest and most posterior of the three **Function** Knee flexion and medial rotation; hip extension; the most used hamstring graft for ACL reconstruction **Tight in** Hip flexion with the knee extended (straight-leg raise) ## Relations **Course** Lies on the [semimembranosus](https://durgical.com/en/anatomy/semimembranosus-muscle/) down the back of the thigh, becomes tendinous in the lower thigh, passes behind the medial femoral condyle and curves forward to the pes anserinus **Deep** Semimembranosus, on which it lies for most of its length **Above** [Gracilis tendon](https://durgical.com/en/anatomy/tendon-of-gracilis/), just above it at the pes anserinus **Lateral** Popliteal fossa, with the [tibial nerve](https://durgical.com/en/anatomy/tibial-nerve/), [popliteal artery](https://durgical.com/en/anatomy/popliteal-artery/) and [popliteal vein](https://durgical.com/en/anatomy/popliteal-vein/) **Superficial** [Sartorius](https://durgical.com/en/anatomy/sartorius-muscle/) aponeurosis at the insertion; fascia and [skin](https://durgical.com/en/anatomy/skin/) higher up ## How to find it Prone, with the knee bent against resistance, it is the sharp cord at the back of the inner knee; the semimembranosus is felt as a broader, softer mass on either side of it and deeper. ## On imaging On MRI or ultrasound after harvest, a new tendon-like structure often regrows along the old path over months; it is not the same as normal tendon. ## Common problems - Strains or tendinitis, mostly in sports with sprinting or kicking. - It is one of the most common graft sources for ACL reconstruction; the leg usually adapts well. ## How it is diagnosed Physical exam; ultrasound or MRI if needed. ## Treatment - Rest, ice and progressive physical therapy. - Used as a tendon graft in ACL reconstruction. ## Clinical notes - Harvest can injure the [saphenous nerve](https://durgical.com/en/anatomy/saphenous-nerve/) or its infrapatellar branch, so the incision and the stripper path are planned with them in mind - Distal ruptures are uncommon, mostly in sprinters; most hamstring injuries are higher, at the muscle–tendon junction or the proximal tendon shared with the biceps femoris - It can snap over the back of the inner knee (snapping pes), a rare cause of medial knee snapping ## Anatomical variants - Accessory slips can join it to the [gracilis](https://durgical.com/en/anatomy/gracilis-muscle/) (a 'double' pes anserinus) or end in the [crural fascia](https://durgical.com/en/anatomy/crural-fascia/) ## Related conditions - [Hamstring Strain](https://durgical.com/en/conditions/hamstring-strain/) ## Test yourself Think of the answer, then tap the question to see it. ## Why is the semitendinosus the first-choice hamstring autograft for ACL reconstruction? Its tendon is long and round, and it is often folded into four strands. ## What must be cut before stripping the semitendinosus tendon, and why? Accessory bands to the fascia of the medial head of gastrocnemius; otherwise the stripper cuts the graft short. ## Which border of the popliteal fossa does the semitendinosus form? The upper medial border, with the semimembranosus. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/tendon-of-semitendinosus/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** musculus semitendinosus TA2 2641 **Official Spanish (DeCS)** Tendón del semitendinoso DeCS D013710 **English (TA2)** Tendon of semitendinosus **Also called** musculus semitendineus ## Related - [Gracilis tendon](https://durgical.com/en/anatomy/tendon-of-gracilis/) - [Pes anserine bursa](https://durgical.com/en/anatomy/anserine-bursa/) - [Semitendinosus](https://durgical.com/en/anatomy/semitendinosus-muscle/) - [Tibia](https://durgical.com/en/anatomy/tibia/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=14088); [Anatomy, Bony Pelvis and Lower Limb: Thigh Semitendinosus Muscle](https://www.ncbi.nlm.nih.gov/books/NBK539862/); [Anatomy, Bony Pelvis and Lower Limb, Hamstring Muscle](https://www.ncbi.nlm.nih.gov/books/NBK546688/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/tendon-of-semitendinosus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/tendon-of-semitendinosus/